Arguments
A.
Arguments are found in many texts and media and it is important to be able to recognize, formulate, and evaluate arguments. Doing well in this class will depend upon whether you can acquire and improve these three skills. We will be concentrating on the arguments found in the philosophy texts we are reading this semester, but this skill is something you should carry with you through the rest of your college career and beyond.
Recognizing an argument is the first step in the process. An argument is where a claim is stated and it is supported by evidence. The claim is the conclusion of the argument and the evidence is known as the premises. In an argument, the conclusion follows from the premises, or, more specifically, the premises connect together in such a way that one can draw an inference from them, i.e., the conclusion.
But recognition of argument is not sufficient. One must also be able to formulate the argument. This involves listing the premises as well as unstated assumptions so one can see more clearly how the conclusion follows from the premises. This task will at first seem tedious and frustrating, but like anything else, the more you practice, the better you will get. Hopefully, you find this exercise beneficial and enlightening.
Here are some sample arguments:
1) All men are mortal.
Socrates is a man.
Socrates is mortal.
2) If there is snow on the ground, it must be cold.
There is snow on the ground.
It must be cold.
3) Animals are either vertebrates or invertebrates.
Walruses, an animal, are not invertebrates.
Walruses are vertebrates.
4) It rained almost every day in April for the last three years.
April is a rainy month.
B.
Not all texts will contain arguments. Some passages will just contain a description, explanation, or dialogue. Here are some examples.
1) Tuesday is the second day of the week.
2) If you do not exercise, you will not be healthy.
3) There are many students who attend state universities. Some explanation for this is that state universities are affordable and offer a variety of disciplines to study.
4) Parent: “You have not cleaned up your room this week.”
Child: “Yes I have.”
Parent: “No, I am afraid your room is still messy.”
Child: “But I have.”
Parent: “No you haven’t, at least not according to me.”
Child: “Well, according to me, I have.”
This last example may seem like an argument because we call it an argument. But this is using the word equivocally, that is using the same word to signify two different things. Example 4 is a disagreement, which does not always constitute an argument. There are no premises to support any claims being made in this example. Further, one should recognize that Example 2 is only a conditional claim and not an argument. A conditional claim is composed of an antecedent and a consequence. One must also affirm the antec.
2024.03.23 What do successful readers do - Sandy Millin for PARK.pptx
ArgumentsA. Arguments are found in many texts and media .docx
1. Arguments
A.
Arguments are found in many texts and media and it is
important to be able to recognize, formulate, and evaluate
arguments. Doing well in this class will depend upon whether
you can acquire and improve these three skills. We will be
concentrating on the arguments found in the philosophy texts
we are reading this semester, but this skill is something you
should carry with you through the rest of your college career
and beyond.
Recognizing an argument is the first step in the process. An
argument is where a claim is stated and it is supported by
evidence. The claim is the conclusion of the argument and the
evidence is known as the premises. In an argument, the
conclusion follows from the premises, or, more specifically, the
premises connect together in such a way that one can draw an
inference from them, i.e., the conclusion.
But recognition of argument is not sufficient. One must also be
able to formulate the argument. This involves listing the
premises as well as unstated assumptions so one can see more
clearly how the conclusion follows from the premises. This
task will at first seem tedious and frustrating, but like anything
else, the more you practice, the better you will get. Hopefully,
you find this exercise beneficial and enlightening.
Here are some sample arguments:
1) All men are mortal.
2. Socrates is a man.
Socrates is mortal.
2) If there is snow on the ground, it must be cold.
There is snow on the ground.
It must be cold.
3) Animals are either vertebrates or invertebrates.
Walruses, an animal, are not invertebrates.
Walruses are vertebrates.
4) It rained almost every day in April for the last three years.
April is a rainy month.
B.
Not all texts will contain arguments. Some passages will just
contain a description, explanation, or dialogue. Here are some
examples.
1) Tuesday is the second day of the week.
2) If you do not exercise, you will not be healthy.
3) There are many students who attend state universities. Some
explanation for this is that state universities are affordable and
offer a variety of disciplines to study.
4) Parent: “You have not cleaned up your room this week.”
3. Child: “Yes I have.”
Parent: “No, I am afraid your room is still messy.”
Child: “But I have.”
Parent: “No you haven’t, at least not according to me.”
Child: “Well, according to me, I have.”
This last example may seem like an argument because we call it
an argument. But this is using the word equivocally, that is
using the same word to signify two different things. Example 4
is a disagreement, which does not always constitute an
argument. There are no premises to support any claims being
made in this example. Further, one should recognize that
Example 2 is only a conditional claim and not an argument. A
conditional claim is composed of an antecedent and a
consequence. One must also affirm the antecedent for the
consequence to follow from this claim. Finally, Example 3 is
an explanation and is not presented as an argument. The author
could have presented this as an argument, but it is more likely
just conveying information. It is essential to distinguish
between information, which is both the premises and the
conclusion by themselves, and an argument, which entails a
relation between both the premises and a conclusion.
C.
To locate an argument, it is beneficial to know several key
words that indicate whether something is a premise or a
conclusion. These are often called “hint words.” The following
list will help pick up arguments in texts:
1) (conclusion) …, for
(premise)
4. 2) (conclusion) …, because
(premise)
3) (conclusion) …, since
(premise)
4) (conclusion) …, as
(premise)
5) (conclusion) …, assuming
that (premise)
6) (premise) …, hence
(conclusion)
7) (premise) …, therefore
(conclusion)
8) (premise) …, so
(conclusion)
9) (premise) …, thus
(conclusion)
10) (premise) …,
consequently (conclusion)
11) (premise) …, for this
reason (conclusion)
These hint words also serve as the connection between the
premises and the conclusion. One should note that some of
these words do not always signify an argument. An example of
this is “for”, which is also used as a preposition – “He used the
shovel ‘for moving dirt’.” One should also note that not all
5. arguments do contain hint words. Be careful. Finally, both the
premises and the conclusion of an argument must form complete
sentences.
D. Here are some pointers for picking out arguments.
1) Look for key words first. If none are found, then look for
anything that sounds like a claim. One important skill you
should acquire is recognizing claims and that claims need
support.
2) Begin with the conclusion, the claim, and then find the
premises, the support for the claim. This is because the
premises will be easier to recognize once you know what you
are trying to prove.
3) Not all premises are explicitly stated. Authors do this
because some things seem obvious, and they are concerned with
the aesthetic quality of their writing or speech. But in the
presentation of an argument, one must always list implicit or
implied premises.
Here are some examples:
#1) John cannot be eligible; he is over twenty.
Argument: Premise 1) John is over twenty
Premise 2) (No one over twenty is eligible.)
Conclusion: John is not eligible.
#2) You should not vote for Jones for he is a child molester.
Argument: Premise 1) Jones is a child molester.
6. Premise 2) (One should not vote for child
molesters.)
Conclusion: One should not vote for Jones.
4) Just as premises are not always stated, so the same applies
for the conclusion.
Here are some examples:
#1) Smith is a liberal, and no good Americans are liberals.
Argument: Premise 1) Smith is a liberal.
Premise 2) No good Americans are liberals.
Conclusion (Smith is not a good American.)
#2) That man has a deadly weapon, and deadly weapons are
dangerous.
Argument: Premise 1) That man has a deadly weapon.
Premise 2) Deadly weapons are dangerous.
Conclusion: (That man is dangerous.)
E.
There are several kinds of arguments that you need to be
familiar with and be able to distinguish. The main two kinds of
arguments are deductive and inductive. The difference between
these two is found in the way the premises relate to the
conclusion. In inductive arguments, the conclusion is only
probable. They are further classified as strong or weak
depending upon how the evidence supports the conclusion. In
section A, example 4 is an inductive argument. It is only likely
7. that April is a rainy month. The evidence presented for the
conclusion does not necessitate it.
Deductive arguments are when the conclusion necessarily
follows from the premises. This means that you cannot doubt
the conclusion if you accept all the premises. In section A,
examples 1, 2, and 3 are deductive arguments. As you will see,
most of the arguments presented in this class will be deductive.
Philosophers are interested in you accepting their arguments.
Deductive arguments are the most powerful and more persuasive
of the two – it is important that you recognize this feature of
deductive arguments.
Finally, there are several other forms of arguments, e.g.,
abductive and dialectical, but these are more controversial and
open for debate. These are better introduced after some
exposure to inductive and deductive arguments.
F.
Now that you have some grasp of recognizing and formulating
arguments, it is appropriate to discuss evaluating arguments.
There are two properties of arguments to determine whether the
argument is good or bad: validity and soundness. One should
note that arguments are never true or false, only valid or
invalid, sound or unsound.
Validity deals with the form or structure of the argument. An
argument is valid if the conclusion follows from the premises.
(This applies to both inductive and deductive arguments.) Since
validity is concerned with the form of the argument, it does not
matter whether the premises are actually true or not. What
matters is that if the premises were all true (and this implies the
possibility of their truth), then the conclusion must be true. Or
in other words, if the premises are all true then it is
inconceivable that the conclusion be false. (This formulation
only applies to deductive arguments. Remember, deductive
8. arguments claim that the conclusion necessarily follows from
the premises.) Here are some examples of valid forms of
deductive arguments.
#1) Modus ponens: If A, then B. #2) Modus tollens:
If A, then B.
A.
not B.
B.
not A.
#3) Exhaustive Disjunction: Either A or B. #4) Basic
Syllogism: All As are Bs.
not A.
All Bs are Cs.
B.
All As are Cs.
#5) Reductio Ad Absurdum: Assume P.
one assumes the opposite
Q. of what you want
to prove. Then you
Not Q. derive a
contradiction and what follows
Not P. is the opposite of
what you assumed
9. There are also several invalid structures with which you should
be familiar.
#1) Affirming the Consequent: If A, then B. #2) Denying the
Antecedent: If A, then B.
B.
not A.
A
not B.
(note: Since these are invalid forms, the conclusion does not
follow from the premises. So, although the author asserts [or
implies] the conclusion, one should not accept it.)
There are also several common fallacies you should know as
well.
#1) Fallacy of equivocation: This is where a word appears in
two or more premises and yet does not contain the same sense in
each use. Example:
Chickens have feathers.
Your friend is a chicken.
Your friend has feathers.
#2) Fallacy of ambiguity: This involves a premise that can be
interpreted in several different ways.
#3) Fallacy of vagueness: This involves a premise that has no
clear interpretation.
The difference between the two terms is important, although
10. note that it is only technical language. Technical language is
used within a certain context to keep track of certain
distinctions, e.g., validity and soundness used above are both
technical terms. The best way to distinguish between ambiguity
and vagueness is to ask whether any interpretation can be
derived from the premises. If more than one can be derived,
meaning one can find two or three or four (some limited,
definite amount), then it is ambiguous. If no definite number of
interpretations can be found, then it is vague.
Finally, when constructing counter-arguments against an author
or speaker, one should avoid these fallacies as well. 1) Ad
hominem: This literally means against the man. One should not
attack the character of the presenter of the argument. The
argument is something distinct from the speaker, for anyone can
make the same argument. 2) Straw man: This is where the
counter-argument does not attack the original argument itself,
but presents a weaker version or something that appears to be
the argument but is not. 3) Tu Quoque: Known as the “You,
too” fallacy, this is more to defend your own argument by
claiming that the other argument makes the same mistake .
Soundness involves both the validity of the argument and the
truth of the premises. For an argument to be sound, it must be
valid and have all true premises. To check for soundness, one
must question the truth of the premises. This involves
constructing an argument that has for its conclusion the
negation of one of the premises of the argument you are
evaluating. You should be careful never to attack the
conclusion of the argument. If you attack the conclusion, you
have only created a dilemma. You now have two arguments
with opposing conclusions, but you do not know which of the
two is the sound argument. This skill is difficult to acquire and
will take much practice to get good at it. One final note: we are
studying good philosophers. If you find something obviously
wrong with their arguments, think again. Remember, you are
11. constructing an argument that itself could be unsound or miss
the point. But do not discount your criticism so quickly either,
instead you should build from that point and think more. The
more you think about the argument, the more you will learn.
Exercises
I. Identify the premises and conclusions in the following
passages, each of which only contains one argument. Do not
forget the implicit premises and conclusions.
1. There must be simple substances because there are
composites; for a composite is nothing else than a collection or
aggregation of simple substances.
2. No man will take counsel, but every man will take money;
therefore, money is better than counsel.
3. God created the universe from nothing; …time did not exist
previously, but was created; for it depends on the motion of the
sphere, and the sphere has been created.
4. …Since there are more people on the earth than hairs on any
person’s head, I know that there must be at least two people
with the same numbers of hairs…
5. It is our duty to do what is right. We have the right to
disregard good advice. Hence, it is our duty to disregard good
advice.
6. All goods are either outside or in the soul, and of these those
in the soul are more desirable… For prudence, virtue, and
pleasure are in the soul, and some or all of these seem to all to
be the end.
7. Even the Fool, then, is forced to agree that than which
nothing greater can be conceived exists in the mind, since he
understands this when he hears it, and whatever is understood is
12. in the mind. And assuredly that than which nothing greater can
be conceived cannot exist in the mind alone. For, suppose it
exists in the mind alone: then it can be conceived to exist in
reality, which is greater. If that which nothing greater can be
conceived exists in the mind alone, then this same that which
nothing greater can be conceived is that which something
greater can be tconceived. But that is impossible.
II. Each of the following passages contains more than one
argument. Distinguish them and identify their premises and
conclusions.
1. …We are told that this God, who prescribes forbearance and
forgiveness of every fault, exercises none himself, but does the
exact opposite; for punishment which comes at the end of all
things, when the world is over and done with, cannot have for
its object either to improve or deter, and is therefore pure
vengeance.
2. There is a perennial classical question that asks which part
of the motorcycle, which grain of sand in which pile, is the
Buddha. Obviously to ask that question is to look in the wrong
direction, for the Buddha is everywhere. But just as obviously
to ask that question is to look in the right direction, for the
Buddha is everywhere.
3. …If Materialism is true, all our thoughts are produced by
purely material antecedents. These are quite blind, and are just
as likely to produce falsehood as truth. We have thus no reason
for believing any of our conclusions – including the truth of
Materialism, which is therefore a self-contradictory hypothesis.
4. Man is good, and better than the cattle because he is capable
of receiving the precept; better still when he has received the
precept; and still better when he has obeyed it; best of all when
he is made happy by the eternal light of wisdom. Sin, or evil,
consists in neglect to receive the precept or to obey it, or to
13. hold fast the contemplation of wisdom. So we learn that, even
although the first man had been created wise, it was
nevertheless possible for him to be seduced. Because his sin
was committed with his free will, a just penalty followed by
divine law.
5. With regard to good and evil, these terms indicate nothing
positive in things
considered in themselves, nor are they anything else than modes
of thought, or notions which we form from the comparison of
one thing with another. For one and the same thing may at the
same time be both good and evil or indifferent. Music, for
example, is good to a melancholy person, bad to one mourning,
while to a deaf man it is neither good nor bad.
1
The ‘Four Principles’ Approach
to Health Care Ethics
TOM L. BEAUCHAMP
My objective is to explain the so-called four principles ap-
proach and to explain the philosophical and practical roles
these principles play. I start with a brief history and then
turn to the four principles framework, its practicality, and
philosophical problems of making the framework specifi c.
THE ORIGINS OF PRINCIPLES IN HEALTH
CARE ETHICS
Prior to the early 1970s, there was no fi rm ground in which
14. a commitment to principles or even ethical theory could
take root in biomedical ethics. This is not to say that phy-
sicians and researchers had no principled commitments to
patients and research subjects. They did, but moral princi-
ples, practices and virtues were rarely discussed. The health
care ethics outlook in Europe and America was largely that
of maximizing medical benefi ts and minimizing risks of
harm and disease. The Hippocratic tradition had neglected
many problems of truthfulness, privacy, justice, communal
responsibility, the vulnerability of research subjects and the
like (Jonsen, 1998; Pellegrino & Thomasma, 1993). Views
about ethics had been largely confi ned to the perspectives
of those in the professions of medicine, public health and
nursing. No sustained work combined concerns in ethical
theory and the health care fi elds.
Principles that could be understood with relative ease
by the members of various disciplines fi gured prominently
in the development of biomedical ethics during the 1970s
and early 1980s. Principles were used primarily to present
frameworks of evaluative assumptions so that they could be
used, and readily understood, by people with many different
forms of professional training. The distilled morality found
in principles gave people a shared and serviceable group of
general norms for analysing many types of moral problems.
In some respects, it could even be claimed that principles
gave the embryonic fi eld of bioethics a shared ‘method’ for
attacking its problems, and this gave some minimal coher-
ence and uniformity to bioethics.
There were two primary sources of the early interest in
principles in biomedical ethics. The fi rst was the Belmont
Report (and related documents) of the National Commis-
sion for the Protection of Human Subjects (Childress et al.,
2005; National Commission for the Protection of Human
16. (a principle requiring respect for the decision-making capaci-
ties of autonomous persons); (2) nonmalefi cence (a principle
requiring not causing harm to others); (3) benefi cence (a
group of principles requiring that we prevent harm, provide
benefi ts and balance benefi ts against risks and costs); (4) jus-
tice (a group of principles requiring appropriate distribution
of benefi ts, risks and costs fairly). I will concentrate now on
an explication of each of the principles and how they are to
be understood collectively as a framework of principles.
RESPECT FOR AUTONOMY
Respect for autonomy is rooted in the liberal moral and
political tradition of the importance of individual freedom
and choice. In moral philosophy personal autonomy refers
to personal self-governance: personal rule of the self by ad-
equate understanding while remaining free from control-
ling interferences by others and from personal limitations
that prevent choice. ‘Autonomy’ means freedom from exter-
nal constraint and the presence of critical mental capacities
such as understanding, intending and voluntary decision-
making capacity (Childress, 1990; Engelherdt, 1996; Katz,
1984; Kukla, 2005). The autonomous individual acts freely
in accordance with a self-chosen plan, analogous to the way
an independent government manages its territories and sets
its policies. A person of diminished autonomy, by contrast,
is in some respect controlled by others or incapable of de-
liberating or acting on the basis of his or her desires and
plans.
To respect an autonomous agent is to recognize with
due appreciation that person’s capacities and perspectives,
including his or her right to hold certain views, to make
certain choices, and to take certain actions based on per-
sonal values and beliefs. The moral demand that we respect
the autonomy of persons can be expressed as a principle of
17. respect for autonomy, which should be stated as involving
both a negative obligation and a positive obligation. As a
negative obligation, autonomous actions should not be sub-
jected to controlling constraints by others. As a positive ob-
ligation, this principle requires both respectful treatment in
disclosing information and actions that foster autonomous
decision making.
Many autonomous actions could not occur without others’
material cooperation in making options available. Respect for
autonomy obligates professionals in health care and research
involving human subjects to disclose information, to probe
for and ensure understanding and voluntariness, and to foster
adequate decision making. True respect requires more than
mere noninterference in others’ personal affairs. It includes,
at least in some contexts, building up or maintaining others’
capacities for autonomous choice while helping to allay fears
and other conditions that destroy or disrupt their autonomous
actions. Respect, on this account, involves acknowledging
the value and decision-making rights of persons and enabling
them to act autonomously, whereas disrespect for autonomy
involves attitudes and actions that ignore, insult, demean or
are inattentive to others’ rights of autonomy.
Many issues in professional ethics concern failures to
respect a person’s autonomy, ranging from manipulative
underdisclosure of pertinent information to nonrecognition
of a refusal of medical interventions. For example, in the
debate over whether autonomous, informed patients have
the right to refuse medical interventions, the principle of re-
spect for autonomy suggests that an autonomous decision to
refuse interventions must be respected. Although it was not
until the late 1970s that serious attention was given to rights
to refuse for patients, this is no reason for thinking that
respect for autonomy as now understood is a newly added
18. principle in our moral perspective. It simply means that the
implications of this principle were not widely appreciated
until recently (Faden & Beauchamp, 1986).
Controversial problems with the principle of respect for
autonomy, as with all moral principles, arise when we must
interpret its signifi cance for particular contexts and deter-
mine precise limits on its application and how to handle
situations when it confl icts with other moral principles.
Many controversies involve questions about the condi-
tions under which a person’s right to autonomous expres-
sion demands actions by others, and also questions about
the restrictions society may rightfully place on choices by
patients or subjects when these choices confl ict with other
values. If restriction of the patient’s autonomy is in order,
the justifi cation will always rest on some competing moral
principles such as benefi cence or justice.
NONMALEFICENCE
Physicians have long avowed that they are obligated to
avoid doing harm to their patients. Among the most quoted
principles in the history of codes of health care ethics is
the maxim primum non nocere: ‘Above all, do no harm’.
British physician Thomas Percival furnished the fi rst
developed modern account of health care ethics, in which
he maintained that a principle of nonmalefi cence fi xes the
physician’s primary obligations and triumphs even over the
principle of respect for the patient’s autonomy in a circum-
stance of potential harm to patients:
To a patient…who makes inquiries which, if faithfully
answered, might prove fatal to him, it would be a gross and
unfeeling wrong to reveal the truth. His right to it is suspended,
and even annihilated; because…it would be deeply injurious to
himself, to his family, and to the public. And he has the
19. strongest
1 THE ‘FOUR PRINCIPLES’ APPROACH TO HEALTH CARE
ETHICS 5
claim, from the trust reposed in his physician, as well as from
the common principles of humanity, to be guarded against
whatever would be detrimental to him (Percival, 1847).
Many basic rules in the common morality are the
requirements to avoid causing a harm. They include rules
such as do not kill, do not cause pain, do not disable, do not
deprive of pleasure, do not cheat and do not break promises
(Gert, 2005). Similar, but more specifi c prohibitions are
found across the literature of biomedical ethics, each
grounded in the principle that intentionally or negligently
caused harm is a fundamental moral wrong.
Numerous problems of nonmalefi cence are found in
health care ethics today – some involving blatant abuses of
persons and others involving subtle and unresolved ques-
tions. Blatant examples of failures to act nonmalefi cently
are found in the use of physicians to classify political dis-
sidents as mentally ill, thereafter treating them with harm-
ful drugs and incarcerating them with insane and violent
persons (Bloch & Reddaway, 1984). More subtle examples
are found in the use of medications for the treatment of ag-
gressive and destructive patients. These common treatment
modalities are helpful to many patients, but they can be
harmful to others.
A provocative question about nonmalefi cence and phy-
sician ethics has been raised by Paul S. Appelbaum in an
investigation of ‘the problem of doing harm’ through testi-
20. mony in criminal contexts and civil litigation – for example,
by omitting information in the context of a trial, after which
a more severe punishment is delivered to the person than
likely would have been delivered. Appelbaum presents the
generic problem as one of nonmalefi cence:
If physicians are committed to doing good and avoiding
harm, how can they participate in legal proceedings from
which harm may result? If, on the other hand, physicians in
court abandon medicine’s traditional ethical principles, how
do they justify that deviation? And if the obligations to do
good and avoid harm no longer govern physicians in the legal
setting, what alternative principles come into play? . . . Are
physicians in general bound by the principles of benefi cence
and nonmalefi cence? (Appelbaum, 1990)
BENEFICENCE
The physician who professes to ‘do no harm’ is not usually
interpreted as pledging never to cause harm, but rather to
strive to create a positive balance of goods over infl icted
harms. Those engaged in medical practice, research and pub-
lic health know that risks of harm presented by interventions
must often be weighed against possible benefi ts for patients,
subjects and the public. Here we see the importance of benef-
icence as a principle beyond the scope of nonmalefi cence.
In ordinary English the term benefi cence connotes acts
of mercy, kindness, charity, love and humanity. In its most
general meaning, it includes all forms of action intended
to benefi t other persons. In health care ethics benefi cence
commonly refers to an action done to benefi t others, whereas
benevolence refers to the character trait or virtue of being
disposed to act for the benefi t of others. The principle of
benefi cence refers to a moral obligation to act for the benefi t
21. of others. No demand is more important when taking care
of patients: the welfare of patients is medicine’s context
and justifi cation. ‘Benefi cence’ has long been treated as a
foundational value – and sometimes as the foundational
value (Pellegrino, 1994; Pellegrino & Thomasma, 1988) – in
health care ethics.
The principle of benefi cence requires us to help oth-
ers further their important and legitimate interests, often
by preventing or removing possible harms. This principle
includes rules such as ‘maximize possible benefi ts and
minimize possible harms’ and ‘balance benefi ts against
risks’. Many duties in medicine, nursing, public health and
research are expressed in terms of a positive obligation to
come to the assistance of those in need of treatment or in
danger of injury. The harms to be prevented, removed or
minimized are the pain, suffering and disability of injury
and disease. The range of benefi ts that might be considered
relevant is broad. It could even include helping patients fi nd
appropriate forms of fi nancial assistance and helping them
gain access to health care or research protocols. Sometimes
the benefi t is for the patient, at other times for society.
Some writers in health care ethics suggest that certain
duties such as not to injure others are more compelling than
duties to benefi t them. They point out that we do not con-
sider it justifi able to kill a dying patient in order to use the
patient’s organs to save two others, even though benefi ts
would be maximized, all things considered. The obligation
not to injure a patient by abandonment has been said to be
stronger than the obligation to prevent injury to a patient who
has been abandoned by another (under the assumption that
both are moral duties). Despite the attractiveness of these
notions that there is a hierarchical ordering rule, Childress
and I reject such hierarchies on grounds that obligations of
benefi cence do, under many circumstances, outweigh those
22. of nonmalefi cence. A harm infl icted by not avoiding caus-
ing it may be negligible or trivial, whereas the harm that
benefi cence requires we prevent may be substantial. For ex-
ample, saving a person’s life by a blood transfusion clearly
justifi es the infl icted harm of venipuncture on the blood do-
nor. One of the motivations for separating nonmalefi cence
from benefi cence is that these principles themselves come
into confl ict. As the weights of the two principles can vary,
there can be no mechanical decision rule asserting that one
obligation must always outweigh the other.
Perhaps the major theoretical problem about benefi cence is
whether the principle generates general moral duties that are
incumbent on everyone – not because of a professional role,
6 PRINCIPLES OF HEALTH CARE ETHICS
but because morality itself makes a general demand of benefi -
cence. Many analyses of benefi cence in ethical theory (most
notably utilitarianism, Kagan, 1989; Miller, 2004; Singer,
1993; 1999) seem to demand severe sacrifi ce and extreme
generosity in the moral life – for example, giving a kidney
for transplantation or donating bone marrow to a stranger.
Consequently, some moral philosophers have argued that such
benefi cent action is virtuous and a moral ideal, but not an ob-
ligation, and therefore that there is no principle of benefi cence
of the sort proclaimed in the four principles approach.
I agree, of course, that the line between what is required
and what is not required by the principle is diffi cult to draw,
and that drawing a precise line independent of context
is impossible. I do not agree, however, with the radical
view that there are no obligations of benefi cence – neither
general nor specifi c obligations. I return to this problem of
23. weighing, judging and specifying below in a discussion of
the notion of prima facie duties.
JUSTICE
Every civilized society is a cooperative venture structured by
moral, legal and cultural principles of justice that defi ne the
terms of cooperation. A person in any such society has been
treated justly if treated according to what is fair, due or owed.
For example, if equal political rights are due all citizens, then
justice is done when those rights are accorded. The more re-
stricted notion of distributive justice refers to fair, equitable
and appropriate distribution in society. Usually this term re-
fers to the distribution of primary social goods such as eco-
nomic goods and fundamental political rights, but burdens
are also within its scope. Paying for forms of national health
insurance is a distributed burden; medical-welfare checks
and grants to do research are distributed benefi ts.
There is no single principle of justice in the four princi-
ples approach. Somewhat like principles under the heading
of benefi cence, there are several principles, each requiring
specifi cation in particular contexts. But common to almost
all theories of justice – and accepted in the four principles
approach – is the minimal (formal) principle that like cases
should be treated alike, or, to use the language of equality,
equals ought to be treated equally and unequals unequally.
This elementary principle, or formal principle of justice,
states no particular respects in which people ought to be
treated. It merely asserts that whatever respects are relevant,
if persons are equal in those respects, they should be treated
alike. Thus, the formal principle of justice does not tell us
how to determine equality or proportion in these matters,
and it lacks substance as a specifi c guide to conduct.
Many controversies about justice arise over what should
24. be considered the relevant characteristics for equal treat-
ment. Principles that specify these relevant characteristics
are often said to be ‘material’ because they identify relevant
properties for distribution. Childress and I take account of
the fact that philosophers have also developed diverse theo-
ries of justice that provide sometimes confl icting material
principles. We try to show that there are some merits in
egalitarian theories, libertarian theories and utilitarian
theories, and we defend a mixed use of principles in these
theories. We think that these three theories of justice all
capture some of our intuitive convictions about justice and
that they can all be tapped as resources that will help to
produce a coherent conception of justice.
However, many issues of justice in health care ethics are
not easily framed in the context of traditional principles and
abstract moral theories (Buchanan, 1997; Buchanan et al.,
2000; Daniels, 1985; 2006; Powers & Faden, 2006). For
example, some basic issues in health care ethics in the last
three decades centre on special levels of protection and aid
for vulnerable and disadvantaged parties in health care sys-
tems. These issues cut across clinical ethics, public health
ethics and research ethics. The four principles approach
tries to deal with several of these issues, without producing a
grand theory for resolving all issues of justice. For example,
we address issues in research ethics about whether research
is permissible with groups who have been repeatedly used
as research subjects, though the advantages of research are
calculated to benefi t all in society. We argue that as medical
research is a social enterprise for the public good, it must be
accomplished in a broadly inclusive and participatory way,
and we try to specify the commitments of such generaliza-
tions. Thus, we incorporate principles of justice but do not
produce a general theory of justice.
25. THE FRAMEWORK OF FOUR PRINCIPLES
AND THE EVOLUTION OF THE THEORY
The choice of our four types of moral principle as the frame-
work for moral decision-making in bioethics derives in part
from professional roles and traditions. As noted earlier,
health professionals’ obligations and virtues have for centu-
ries (as found in codes and learned writings on ethics) been
framed by professional commitments to provide medical
care and to protect patients from disease, injury and system
failure. Our principles build on this tradition, but they also
signifi cantly depart from it by including parts of morality
that traditionally have been neglected in health care ethics,
especially through the principles of respect for autonomy
and justice. All four types of principles are needed to pro-
vide a comprehensive framework for biomedical ethics, but
this general framework is abstract and spare until it has
been further specifi ed – that is, interpreted and adapted for
particular circumstances.
Principles of Biomedical Ethics has evolved appreciably
since the fi rst edition in its understanding of abstractness
and the demands of particular circumstances. This is not
1 THE ‘FOUR PRINCIPLES’ APPROACH TO HEALTH CARE
ETHICS 7
because the principles have changed, but because over the
years Childress and I have altered some of our views about
the grounding of the principles and about their practical sig-
nifi cance. Two major changes deserve special attention. The
fi rst is our development of the idea that the four principles
are already embedded in public morality – a universal com-
mon morality – and are presupposed in the formulation of
26. public and institutional policies. The second is our adoption
of Henry Richardson’s account of the specifi cation of moral
norms. These changes of theory and their signifi cance will
be discussed in the next two sections.
THE CENTRALITY OF THE COMMON
MORALITY
The source of the four principles is what we, Childress and
I, call the common morality (a view only incorporated at
the point of the third edition of Principles, following the
language of Alan Donagan). The common morality is appli-
cable to all persons in all places, and all human conduct is
rightly judged by its standards. The following are examples
of standards of action (rules of obligation) in the common
morality: (1) ‘do not kill’; (2) ‘do not cause pain or suffer-
ing to others’; (3) ‘prevent evil or harm from occurring’;
(4) ‘rescue persons in danger’; (5) ‘tell the truth’; (6) ‘nur-
ture the young and dependent’; (7) ‘keep your promises’;
(8) ‘do not steal’; (9) ‘do not punish the innocent’; (10) ‘treat
all persons with equal moral consideration’.
Why have such norms become parts of a common moral-
ity, whereas other norms have not? To answer this question,
I start with an assumption about the primary goal – that is,
objective – of the social institution of morality. This objec-
tive is to promote human fl ourishing by counteracting con-
ditions that cause the quality of people’s lives to worsen. The
goal is to prevent or limit problems of indifference, confl ict,
suffering, hostility, scarce resources, limited information,
and the like. Centuries of experience have demonstrated
that the human condition tends to deteriorate into misery,
confusion, violence and distrust unless norms of the sort
just listed (1–10) – the norms of the common morality – are
observed. When complied with, these norms lessen hu-
man misery and preventable death. It is an overstatement
27. to maintain that all of these norms are necessary for the
survival of a society (as some philosophers and social sci-
entists have maintained (Bok, 1995), but it is not too much
to claim that these norms are necessary to ameliorate or
counteract the tendency for the quality of people’s lives to
worsen or for social relationships to disintegrate (Mackie,
1977; Warnock, 1971).
These norms are what they are, and not some other set of
norms, because they have proven over time that their obser-
vance is essential to realize the objectives of morality. What
justifi es them is that they achieve the objectives of morality,
not the fact that they are universally shared across cultures. It
is conceivable, of course, that the set of norms that is shared
universally is not the same set of norms as the set pragmati-
cally justifi ed by their conformity to the objectives of moral-
ity. I agree that if another set of norms would better serve
the objectives of morality, then that set of norms ought to
displace the norms currently in place. However, I believe that
there are no good candidates as alternatives to these norms.
What Childress and I call ‘principles’ simply are the most
general and basic norms of the common morality. In Prin-
ciples of Biomedical Ethics, we devote an entire chapter to
each principle in the attempt to explain its nature, content,
specifi cation and the like. The assumption behind the argu-
ment in each chapter is that our framework of four prin-
ciples should incorporate and articulate the most general
values of the common morality.
Our framework encompasses several types of moral
norms, including not only principles, but also rules, rights
and moral ideals. We treat principles as the most general
and comprehensive norms, but we make only a loose dis-
tinction between rules and principles. Rules, we argue, are
28. more precise and practical guides to action that depend on
the more general principles for their justifi cation. We de-
fend several types of rules, all of which should be viewed
as specifi cations of principles. These include substantive
rules (e.g. truth telling, confi dentiality and privacy rules),
authority rules (e.g. rules of surrogate authority and rules of
professional authority) and procedural rules (e.g. rules for
determining eligibility for organ transplantation and rules
for reporting grievances to higher authorities).
THE PRIMA FACIE CHARACTER OF PRINCIPLES
AND RULES
These principles and rules (or other norms in the common
morality) can in some circumstances be justifi ably over-
ridden by other moral norms with which they confl ict. For
example, we might justifi ably not tell the truth in order to
prevent someone from killing another person, and we might
justifi ably disclose confi dential information about a person
in order to protect the rights of another person. Principles,
duties and rights are not absolute (or unconditional) merely
because they are universal. There are exceptions to all prin-
ciples, each of which is merely presumptive in force.
Oxford philosopher W. D. Ross developed a theory that
has been part of Principles since the fi rst edition. Ross’s
theory is intended to assist in resolving problems of confl ict
between principles. His views are based on an account of
prima facie duties, which he contrasts with actual duties. A
prima facie duty is one that is always to be acted upon unless
it confl icts on a particular occasion with another duty. One’s
8 PRINCIPLES OF HEALTH CARE ETHICS
29. actual duty, by contrast, is determined by an examination
of the respective weights of competing prima facie duties in
particular situations. When principles contingently confl ict,
no supreme principle is available – in the four principles
approach – to determine an overriding obligation. There-
fore, discretionary judgement becomes an inescapable part
of moral thinking that relies on principles.
Here is an example. A physician has confi dential in-
formation about a patient who is also an employee in the
hospital where the physician practises. The employee is
seeking advancement in a stress-fi lled position, but the phy-
sician has good reason to believe this advancement would
be devastating for both the employee and the hospital. The
physician has duties of confi dentiality, nonmalefi cence and
benefi cence in these circumstances. Should the physician
break confi dence? Could the matter be handled by making
thin disclosures only to the hospital administrator and not
to the personnel offi ce? Can such disclosures be made con-
sistent with one’s general commitments to confi dentiality?
Addressing these questions through a process of moral jus-
tifi cation is required to establish one’s actual duty in the face
of these confl icts of prima facie duties. I will discuss how
this is to be done in the section below on specifi cation.
Once we acknowledge that all general principles have
exceptions, we are free to view every moral conclusion that
is supported by a principle and every principle itself as sub-
ject to modifi cation or reformulation. Change of this sort
is to be accomplished through specifi cation, the means by
which principles come to have real practical value.
THE SPECIFICATION OF PRINCIPLES
AND RULES
To say that principles have their origins in and fi nd sup-
30. port in the common morality and in traditions of health care
is not to say that their appearance in a developed system
of biomedical ethics is identical to their appearance in the
traditions from which they spring. Many authors have cor-
rectly pointed out that prima facie principles underdeter-
mine moral judgements because there is too little content
in such abstract principles to determine concrete outcomes.
Every norm and theory contains regions of indeterminacy
that need reduction through further development of their
commitments in the system, augmenting them with a more
specifi c moral content. I turn, then, to these questions: ‘How
does the prima facie conception of principles work in prac-
tical bioethics?’; ‘How are general principles to reach down
to concrete policies?’; ‘How does one fi ll the gap between
abstract principles and concrete judgements?’
The answer is that principles must be specifi ed to suit the
needs and demands of particular contexts, thus enabling
principles to overcome their lack of content and to handle
moral confl ict. Specifi cation is a process of reducing the
indeterminateness of abstract norms and providing them with
specifi c action-guiding content (Degrazia & Beauchamp,
2001; DeGrazia, 1992; Richardson, 1990; 2000). For exam-
ple, without further specifi cation, ‘do no harm’ is too abstract
to help in thinking through problems such as whether physi-
cians may justifi ably hasten the death of patients. The general
norm has to be specifi ed for this particular context.
Specifi cation is not a process of producing or defending
general norms such as those in the common morality; it as-
sumes that they are available. Specifying the norms with
which one starts (whether those in the common morality
or norms that were previously specifi ed) is accomplished
by narrowing the scope of the norms, not by explaining
what the general norms mean. The scope is narrowed, as
31. Henry Richardson puts it, by ‘spelling out where, when,
why, how, by what means, to whom, or by whom the action
is to be done or avoided’ (Richardson, 2000). For example,
the norm that we are obligated to ‘respect the autonomy of
persons’ cannot, unless specifi ed, handle complicated prob-
lems of what to disclose or demand in clinical medicine and
research involving human subjects. A defi nition of ‘respect
for autonomy’ (as, say, ‘allowing competent persons to ex-
ercise their liberty rights’) might clarify one’s meaning in
using the norm, but would not narrow the general norm or
render it more specifi c.
Specifi cation adds content to general norms. For example,
one possible specifi cation of ‘respect the autonomy of per-
sons’ is ‘respect the autonomy of competent patients when
they become incompetent by following their advance direc-
tives’. This specifi cation will work well in some medical
contexts, but will not be adequate in others, thus necessi-
tating additional specifi cation. Progressive specifi cation can
continue indefi nitely, gradually reducing the confl icts that
abstract principles themselves cannot resolve. However, to
qualify all along the way as a specifi cation, some transpar-
ent connection must always be maintained to the initial norm
that gives moral authority to the resulting string of norms.
Now we come to a critical matter about particular mo-
ralities, by contrast to the common morality. There is al-
ways the possibility of developing more than one line of
specifi cation of a norm when confronting practical prob-
lems and moral disagreements. It is simply part of the moral
life that different persons and groups will offer different
(sometimes confl icting) specifi cations, potentially creating
multiple particular moralities. On any problematic issue
(such as abortion, animal research, aid in disaster relief,
health inequities, euthanasia, etc.) competing specifi cations
are likely to be offered by reasonable and fair-minded par-
32. ties, all of whom are committed to the common morality.
We cannot hold persons to a higher standard than to make
judgements conscientiously in light of the relevant basic and
specifi ed norms, while attending to the available factual
1 THE ‘FOUR PRINCIPLES’ APPROACH TO HEALTH CARE
ETHICS 9
evidence. Conscientious and reasonable moral agents will
understandably disagree with equally conscientious per-
sons over moral weights and priorities in circumstances of
a contingent confl ict of norms.
Nothing in the model of specifi cation suggests that we
can always eliminate circumstances of intractable confl ict-
ing judgements. However, we should always try to do so by
justifying whatever specifi cation we put forward. This sug-
gests that specifi cation as a method needs to be connected
to a model of justifi cation that will support some specifi ca-
tions and not others. Only brief attention can be paid here
to this diffi cult philosophical problem.
JUSTIFYING SPECIFICATIONS USING
THE METHOD OF COHERENCE
A specifi cation is justifi ed, in the four principles approach,
if and only if it maximizes the coherence of the overall set
of relevant, justifi ed beliefs. These beliefs could include
empirically justifi ed beliefs, justifi ed basic moral beliefs
and previously justifi ed specifi cations. This is a version of
so-called wide refl ective equilibrium (Daniels, 1979; 1996).
No matter how wide the pool of beliefs, there is no reason
to expect that the process of rendering norms coherent by
specifi cation will come to an end or be perfected. Particular
33. moralities are, from this perspective, continuous works in
progress – a process rather than a fi nished product. There
is no reason to think that morality can be rendered coherent
in only one way through the process of specifi cation. Many
particular moralities present coherent ways to specify the
common morality. Normatively, we can demand no more
than that agents faithfully specify the norms of the common
morality with an attentive eye to overall coherence.
The following are some of the criteria for a coherent (and
therefore, according to this model, justifi ed) set of ethical
beliefs: consistency (the avoidance of contradiction); ar-
gumentative support (explicit support for a position with
reasons); intuitive plausibility (the feature of a norm or
judgement being secure in its own right); compatibility or
coherence with reasonable nonmoral beliefs (in particular,
coherence with available empirical evidence); comprehen-
siveness (the feature of covering the entire moral domain or
as much of it as possible); simplicity (reducing the number
of moral considerations to the minimum possible without
sacrifi ce in terms of the other criteria) (DeGrazia, 2003;
DeGrazia & Beauchamp, 2001).
CONCLUSION
I have explained, and argued in defence of, what has often
been called the four principles approach to biomedical eth-
ics, and now increasingly called principlism (Arras, 1994;
Gert et al., 1997; Evans, 2000; Strong, 2000; Winkler,
1996). The four clusters of principles derive from both con-
sidered judgements in the common morality and enduring
and valuable parts of traditions of health care. Health care
ethics has often been said to be an ‘applied ethics’, but this
metaphor may be more misleading than helpful. It is rarely
the case that we simply apply a principle to resolve a tough
34. problem. We will almost always, I have argued, be engaged
in collecting evidence, reasoning and specifying general
principles. This is how problems should be treated and how
progress can be made in health care ethics. From this per-
spective, the four principles form only a starting point – the
point where the practical work begins.
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Via encouraging increasingly accessible, reliable and user-
friendly ways to interrogate and visualise geographic data, open
source GIS methods are providing enormous scope for greater
and more widespread understanding of spatial patterns across a
multitude of fields and applications (Steiniger and Bocher,
2009). The visualisations created as part of this assessment aim
to demonstrate how a range of these open source tools and
software can be utilised in order to analyse and present spatial
data in ways where it can have an informative and meaningful
impact upon its audience. The patterns and messages revealed
by the visualisations will consequently be discussed and
comment will be made upon any limitations of the maps created
39. and challenges encountered whilst putting the GIS methods into
practise.
The first geovisualisation (Figure 1) presented consists of a
series of heat maps showing the spatial pattern of road traffic
collisions (RTC) in the borough of Manhattan, New York City
(NYC) over a period of three years. Using a series of small,
similar maps offers the benefit of visually enforcing the
comparison of changes within them (Tufte, 1991). With this in
mind, the small multiples approach was the ideal method for
visualising and comparing the different spatial patterns of RTC
causes. The idea behind this visualisation was to identify areas
of high collision concentration both overall and in terms of
specific causes. Highlighting where these “hotspots” occur may
help authorities to understand why high numbers of collisions
are concentrated in certain locations and therefore help to
formulate measures to improve road safety.
The dataset used in this visualisation was sourced from the
NYC Open Data website and is a product of all RTC recorded in
the New York Police Department database between the 7th
January 2012 and the 31st December 2014. The data was
downloaded in the form of a CSV file with georeferenced fields
for the majority of cases included. Once downloaded, the data
was imported to QGIS using the “Add delimited text layer”
function with geometry defined using the latitude and longitude
fields. This could then be converted to a shapefile consisting of
103,398 individual georeferenced points. By filtering this
dataset using different criteria, I was able to create new
shapefiles for a number of different causal factors. These, along
with the original unfiltered shapefile could then be used to
create individual heat maps with the QGIS Heatmap Plugin.
Ensuring the heat maps effectively displayed patterns in the
data required significant experimentation, a large part of which
was finding a suitable radius. Too large a radius, for example,
would distort the pattern of collisions by suggesting they
occurred over excessively wide an area. Given that the overall
dataset being used contained over 100,000 points covering an
40. area of around 90km2, a fairly small radius of 300m was
chosen.
The basemap used in the visualisations consisted of vector lines
data sourced from the Open Street Map (OSM) project. This was
downloaded as a KML file, converted to a shapefile and clipped
to the Manhattan boundary. Use of the basemap was important
as the location and size of roads provided some useful context
to the information on collisions. A grayscale basemap was
chosen as it showed up most effectively beneath the coloured
raster surfaces of the heatmaps. Labels for a number of major
roads were added for further context using an additional filtered
OSM layer.
Observation of the heatmap for total collisions shows us that the
highest concentrations of RTCs are located around major road
intersections close to 60th Street, the Lincoln Tunnel and two
major bridges on the south of the island. Generally, the lower
half of the island appears to experience a greater number of
collisions than the upper half. Hotspots for collisions involving
slippery roads can be identified along Henry Hudson Parkway
and also in the Noho area near to Williamsburg Bridge.
Speeding collisions appear to have a distribution less centred on
the busy Midtown area of the borough. For example, hotspots
can be found in the Financial District and along Broadway on
the Upper West Side. Finally, road-rage related collisions show
the greatest concentration in busy areas just south of Central
Park.
The RTCs visualisation demonstrates the potential of the QGIS
heat map function as a means of identifying spatial patterns.
However, major challenges exist with regard to the scale at
which the analysis is being carried out and the consequent
definition of suitable parameters such as heatmap radius. These
challenges should be viewed with particular caution in light of
the wider non-expert user base which open source GIS is
making map production accessible to. In terms of the
visualisation presented here, the main limitations relate to the
level of detail shown. The decision to highlight collision
41. patterns on a boroughwide scale means that to some extent, the
precision of individual collision locations had to be sacrificed.
One way of overcoming this problem of scale would be to
present the data as an interactive web map with the ability to
zoom in on specific point locations.
Figure 1. Road traffic collisions in Manhattan, NYC.
The second visualisation (Figure 2) displays the distribution of
English Heritage listed buildings across London’s boroughs.
The data involved consisted of over 18,000 individual points
situated within the area of Greater London. Due to its suitability
for summarising densities of large numbers of points (Graser,
2013,) a hexagonal binning approach was chosen to visualise
the distribution of London’s listed buildings.
The data was sourced from the English Heritage website,
located via a search using the government open data portal.
After downloading the data as a CSV, it was imported into
QGIS and converted into a shapefile. Following this, the
georeferenced point layer was clipped using a polygon
representing the Greater London boundary. This polygon was
constructed by filtering a national layer of unitary authority
boundaries. Using the “hex grid from layer bounds” function in
the QGIS processing toolbox, a 2km2 hexagonal grid was
created covering the extent of the listed buildings points which
could then be used in a “count points in polygon” operation.
Choosing a suitable resolution for this grid was key to
achieving an effective visualisation. A number of different
resolutions were tested and following experimentation I decided
that 2km was sufficient resolution to display boroughlevel
variations in listed building density without being so fine-
grained that overall clarity was sacrificed. The new hexagonal
grid layer containing information on listed building numbers
could then be clipped to the Greater London boundary and
styled using no outline and a graduated colour scheme based on
42. a natural breaks classification. Borough outlines and labels were
consequently added to provide context.
Figure 2 shows that higher concentrations of listed buildings
generally exist in central areas of London. In terms of boroughs,
the highest concentration appears to occur in Westminster.
Outer boroughs show much lower concentrations of listed
buildings, particularly in the south and east of the city. Barking
and Dagenham seems to contain the least listed buildings in the
city, with only three areas where the concentration of listed
buildings per 2km2 exceeds 3. The apparent negative
relationship between distance from London’s centre and
concentration of listed buildings can be explained by a number
of factors, one of which may be the age of buildings. The
English Heritage website states that “the older a building is, the
more likely it is to be listed”. London’s historical growth from
the centre outwards may hence explain why more, older
buildings and hence more, listed buildings lie near to the centre
of the city. The pattern of low listed building concentrations in
eastern boroughs of the city may, to an extent, represent the
effects of bombing in the Second World War. However, perhaps
the most important factor underlying the patterns of listed
building concentration demonstrated is the general density of
the built environment. The fact that the number of all buildings
per 2km2 in central London is significantly higher than in outer
boroughs logically increases the probability that the number of
listed buildings will also be higher.
The hex-bin approach used in this visualisation demonstrates an
alternative method to the heatmap when visualising point
density. Significant caution was required when selecting a
radius distance for the heatmaps in Figure 1 and this was again
necessary when defining the area of hexagons used in Figure 2.
An issue with regard to the aggregation of points to any larger
areas, in this case a 2km2 hexagonal grid, is that an assumption
of uniformity is made. This assumption rarely holds. Parallels
can be drawn with examples in raster data, where, despite sub-
pixel variations, a pixel must take on a single value to
43. represent, e.g. a landcover type (Fisher, 1997). With the hex-bin
map presented here, some variation in listed building density
may occur below the level of the 2km2 hexagon and hence
remain undetected. For example, five listed buildings may occur
in one street within a hexagon yet the remaining area may be
completely devoid of them.
Figure 2. English Heritage listed buildings, London.
The final visualisation presented consists of an interactive web
map created using Google Fusion Tables:
https://www.google.com/fusiontables/DataSource?docid=18rPxF
U67BsWooVrr23X0NdLRc W-nim04FZS6ucDO.
The map displays European countries using a choropleth map
coloured on the basis of the number of Summer Olympic medals
won (1896-2008) per 1000 members of their respective
populations (Figure 3). More detail, including total medal
count, estimated population and most successful Olympic
Games is provided via an info-window which appears on the
clicking of individual countries.
All data on Olympic medals was sourced from the International
Olympic Committee (IOC) Research and Reference Service via
The Guardian Data Blog website. International boundary data
was downloaded as part of the Natural Earth admin countries
dataset. The first step in creating the visualisation was to
identify the data that I wished to include and to organise this in
a suitable tabular format in Excel. This involved applying a
number of filters to the IOC data, adding a field for estimated
population and calculating a field for medals per 1000 people.
Next, a unique identifier field was added to the table which
matched a corresponding field in the geographical boundary
data. Following the import of the medals data to QGIS as a
CSV, this unique identifier field could be used to create a
tabular join between the medals and boundary data. The
resulting joined data could then be saved as a shapefile and a
44. KML which could consequently be uploaded for use in Google
Fusion Tables.
Styling of the data on Google Fusion Tables involved using
“buckets” to control fill colour on the basis of values within the
“medals per 1000” field. I experimented with different
classification schemes in QGIS before deciding on a quantile
classification using 8 classes and consequently copying the
break values into Google Fusion Tables. A sequential colour
scheme was chosen in QGIS and hex-codes copied in. The info-
window was reorganised by editing the window’s HTML code.
This involved selecting the fields to be included and altering the
order, style and format in which they would be displayed.
The Olympic medals visualisation shows us that the most
successful countries in terms of medals per 1000 include the
Scandinavian countries as well as Hungary. Through use of the
info-window, a possible trend of countries with smaller
populations having more medals per person can be identified. A
pattern of low Olympic success in recently formed countries
such as the Czech Republic, Bosnia and Herzegovina and Serbia
is clearly evident in the visualisation. This is a product of the
lower number of Olympic Games they have taken part in
compared to their older neighbours.
The process of producing the Olympic medals web map was
extremely straightforward, firstly due to the flexibility of QGIS,
exemplified by the conversion of data from shapefile to KML
form. Once the data was uploaded, the functionality of Google
Fusion Tables, for example the option to view and edit fields in
the attribute table, enabled me to experiment with a number of
different map options before deciding on my preferred choice.
One aspect of Google Fusion Tables that I felt was limited
involved the creation of classes in the styling of the map and
consequent colour scheme selection. Creating an option to
classify data via a choice of algorithms and improving the range
of pre-loaded colour schemes would prevent the need to copy in
break values and hex codes from QGIS. Significant time could
be spent improving the Olympic medals web map, much of
45. which would involve adding more data and further
experimenting with display options in the info-window. For
example, adding a field for most successful sport, images of
national flags or perhaps a second layer representing success at
Winter Olympics.
The three visualisations presented here: a series of heatmaps, a
hex-bin map and an interactive web map, demonstrate some of a
wide range of geo-spatial techniques that open source GIS
software makes freely available and accessible. Despite the
great potential that open source GIS offers, the techniques
involved have been shown to have their limitations, particularly
if being used by a non-GIS expert. However, via thoughtful use
of these techniques, I have been able to highlight important
spatial trends which further our understanding of the phenomena
being studied and have the potential to inform future decision
making.
Figure 3. Olympic medals visualisation. Screenshot from
Google Fusion Tables.
References
English Heritage, Listed buildings. Available from:
http://www.englishheritage.org.uk/caring/listing/listed-
buildings/[last accessed: 18/01/2015]
Fisher, P. (1997). The pixel: a snare and a delusion.
International Journal of Remote Sensing, 18(3), 679-685.
Graser, A. (2013). Learning QGIS 2.0. Packt Publishing Ltd.
Guardian Data Blog, If Michael Phelps were a country, how
would his medal haul compare? Available from:
http://www.theguardian.com/sport/datablog/2012/aug/01/ifmich
ael-phelps-were-a-country[last accessed: 18/01/2015]
IOC Research and Reference Service. Available from:
http://www.olympic.org/content/theolympic-studies-
centre/service-pages-container/the-research-and-reference-
service/[last accessed: 18/01/2015]
New York City Open Data, NYPD motor vehicle collisions.
46. Available from:
https://data.cityofnewyork.us/NYC-BigApps/NYPD-Motor-
Vehicle-Collisions/h9ginx95[last accessed: 18/01/2015]
Open Street Map. Available from:
https://www.openstreetmap.org/#map=13/52.1441/-
0.4683[last accessed: 18/01/2015]
Steiniger, S., & Bocher, E. (2009). An overview on current free
and open source desktop GIS developments. International
Journal of Geographical Information Science, 23(10), 1345-
1370.
Tufte, E. R. (1991). Envisioning information. Optometry &
Vision Science, 68(4), 322-324.
TRP620 Open Source GIS and Spatial Data Analysis
Geoprocessing and Map Styling in QGIS
Session led by Ruth
Hamilton
Introduction
Part 1
For the first part of this practical, we are going to think about
how best to display point data.
47. This map shows the highest point in each county in the US.
Your brain can tell you that there are lots of points on the map
and that there are probably hotspots in certain locations but
once you have hundreds of points in a small area like this, it’s
very difficult to process this information mentally or to really
distinguish any patterns. For example, we can see the density of
points is higher in the east of the US than the west, but we can’t
identify much beyond that.
We are going to look at two simple approaches, that allow us to
lighten the cognitive load of points maps like the one above and
make sense of the data. This makes it much easier to then
interpret the underlying spatial patterns. The methods we are
going to look at are:
->Heatmaps and
-> Hex-bins
Part 2
In the second part of today’s session, we will be creating an A0
size map of Sheffield using Ordnance Survey open data – after
undertaking a number of simple geoprocessing steps. In case
you didn’t already know, Ordnance Survey is the national
mapping agency for Great Britain and has a wide range of open
data available for use.
We’re going to do the following things in this part of the
workshop…
· Download a number of different layers from the OS OpenData
web portal.
· Dissolve a layer based on a common attribute
· Buffer the boundary of Sheffield to 20km so we can define a
reasonable area of interest.
· Clip our layers using our buffered Sheffield boundary.
48. After we’ve done this we will then download apply layer
stylesheets to use in QGIS. A stylesheet allows you to
automatically symbolise a layer and Ordnance Survey have a
range of stylesheets you can use with QGIS so that you can
mimic their famous map styles.
The end result of the session should be an A0 size (84.1 x 118.9
cm) map of Sheffield which looks something like the image on
the next page.
Once you understand the method and how stylesheets work you
can then apply the technique to other areas and produce a map
of a different area of the country, if you wish.
As always, please remember to use an external hard drive or – if
you’ve forgotten it – the C drive of the machine you are
working on.
Some of the downloads today are quite big so don’t worry if it
takes a little while to download the data.
Part 1
Task 1: Creating a heatmap from points
Sometimes when you have hundreds, thousands or even millions
of points clustered together it can become hard to interpret
them. One way that can help summarise patterns like this is
called a ‘heatmap’; this interpolates discrete points to create a
continuous surface representing the density of points.
The simplest way of creating a visual heat map of point is to use
the Heatmap symbology option.
· Add the ‘AllSchools_ShefBNG’ shapefile to QGIS for this
task.
49. · Open the symbology tab of the properties box and select the
Heatmap option as shown.
· Click ‘Apply’ and look at your data. Zoom in and out.
You should see that the heatmap clustering changes and
disaggregates as you zoom in. This is useful for visualisation
purposes but because is calculated dynamically - depending on
the zoom scale - it can sometimes be unhelpful. We can also
calculate a heatmap that uses a fixed radius and so doesn’t
change as the zoom level changes. This is shown on the next
page.
Tip: An alternative way of rendering point layers is point
clustering. This option is also accessed from the renderer drop-
down menu in the Symbology tab. This results in a point cluster
symbol that indicates the number of points that overlap in that
area. Like the heatmap renderer this will change as you zoom in
and out. You see this kind of visualisation a lot in online maps
but you can also use in printed maps.
You can also create heatmap layer in QGIS using the
Interpolation tool. Rather than changing the way the data is
visualised, this creates a new, raster layer that is fixed
irrespective of zoom level. You can find this by opening the
Processing toolbox (Processing > Toolbox) and typing
‘heatmap’ into the search box
· The first thing I want you to do is follow the very basic
example on the next page which shows you how to create an
interpolated heatmap. This is not very revealing and is just a
quick example of how to the plugin works.
· Instead of the default values, I want you to enter 2500 as the
radius (this indicates a radius of 2.5km) and make sure you
change the pixel size to at least 10 – you don’t need to touch
any of the other settings.
50. · Once you’ve done this you will see a new black to white
coloured raster surface called Heatmap.
· Go into the properties for the layer and change it to a different
style by going to the colour options (via Style) and then
changing the Render type to ‘Singleband pseudocolor’.
· Select a colour scheme and then you just need to click Load
(bottom right) and then Classify – I have also ticked the ‘Invert’
box so the colour scheme runs from blue to red. The final
product should look something like the image below.
· It may helpful if you add a basemap (Web>OpenLayersPlugin)
and change the transparency of the Heatmap layer (for a raster
layer, you do this from the transparency tab).
This gives you a raster surface image that indicates the density
of schools in Sheffield. Note, how this heat map remains the
same as you zoom in and out.
Making a heatmap of locations like this doesn’t always make
sense from an analytical point of view. What I want you to think
about is what kind of data might be more suitable for this kind
of analysis. Two data examples that should come to mind
immediately are crime data and fire incident data. You can find
some interesting fire incident data for London at the link below.
This could make for an interesting and relevant heat map! The
other link is for crime data, via police.uk.
· http://data.london.gov.uk/dataset/london-fire-brigade-incident-
records
· http://data.police.uk/data/
The question of what radius you should specify is, of course, a
very important issue and will vary from dataset to dataset, there
51. needs to be some kind of distance decay function but precisely
what this should be is up to you as the analyst.
Caution: The Heatmap plugin in QGIS can generate some lovely
looking maps but there is a danger that what you produce can be
misleading and/or simply wrong. What you must be careful to
do when presenting the results of any heat mapping is to declare
your method and say why you took such an approach. Without
such information a heatmap is much more difficult to interpret.
Task 2: Mapping density with hex grids
Mapping densities using a hexagonal grid is an increasingly
common method in spatial analysis – and is a useful alternative
to creating heatmaps. Search online now for ‘hex binning gis’ or
look at the links below. Follow up on this afterwards if you
want to learn more.
· https://datavizproject.com/data-type/hexagonal-binning/
· https://odileeds.org/blog/2017-05-08-mapping-election-with-
hexes
· https://blog.mapbox.com/binning-an-alternative-to-point-
maps-2cfc7b01d2ed
It’s a very effective approach if you have lots of points and has
some advantages over heatmaps.
We are going to have a go using the schools dataset we have
just used.
· First, we are going to create a hex-bin shapefile that covers
the geographical extent we are interested in, this is just a
polygon shapefile which is tiled with identical polygons. These
have no value to start with but we are then going to use the
‘Points in polygon’ tool to calculate the number of points from
the schools layer that are within each hexagon.
In QGIS version 3.2, you do this from MMQGIS menu (you may
have to install the MMQGIS plugin first). Select Create
followed by Create Grid Layer. Then fill in the dialog box as
52. shown in the picture below:
4. Select a location and name for the output file
3. Make sure this is your Schools layer
2. This should be set to Layer Extent
1. This should be set to ‘Hexagons’
2. Set this to ‘layer extent’
3. Select your layer here – in this case the schools layer
4. Select a location for your ‘grid’ layer and click OK
· After you’ve created your new hex bin layer you need to add
the school data to it. Do this by using the ‘Points in polygon’
tool from the Vector > Analysis menu. This will count the
number of points in each hexagon and add that as an attribute
to the hex-grid layer.
This is the attribute field that will contain the ‘count’ of points
This is the layer you want to ‘count’
This is the hex-grid layer
· Symbolise the layer using the NUMPOINTS field as shown
below – and the result will similar to the image on the next
page. This shows the density of schools in Sheffield on a hex
grid. You can use the ‘Count points in polygon (weighted)’ tool
if you want to use the values in an attribute (for example,
population counts) to weight your point shapefile. You can find
this tool by searching in the Processing toolbox.
· Once you’ve created the heatmap and the hexbinned data, add
53. a base map (Web > OpenLayers Plugin) and experiment with
colours and transparencies until you get a map that you like.
· Compare the two approaches and think about how they could
be used.
· Again, crime data and fire incident data may be more useful
examples of when we could use hex binning. The example
below is one I produced using London fire data from 2012 to
2014.
Part 2
An explanation of the British National Grid
The British National Grid – or Ordnance Survey National Grid
reference system – divides Great Britain up into a number of
different areas based on a lettering system. It is a little more
complicated in reality but that’s what you need to know for
now.
When you download data from OS OpenData (or Digimaps) you
will often get data relating to an individual ‘tile’, which has a
two letter code – as you can see below. Very often, the area you
want to map will overlap two tiles.
I created the shapefile shown to the right so you can find your
way around and understand what data you need if you want to
map other areas. As shown below, Sheffield (just) overlaps the
SE and SK tiles but we are going to ignore this for today and
work with the SK tile.
I have placed the tile shapefile (OS_opndata_2letters.shp) in the
Data Folder on MOLE because it can often save you time if you
add it to QGIS, turn on an underlying base layer (e.g. Google
Streets) and then figure out exactly which tile you need. It’s
much easier this way! You don’t need to use it today, but feel
free to use it if you wish.
Task 1: Get the Data
54. There are a few different datasets you need to download today.
DO NOT follow my instructions below. I am including these for
reference because I want you to know about different data
sources. The files downloaded from these sites are very large
and include much more than required for this workshop.
Instead, use the data I have made available on the Blackboard
page.
1. Go to the OS Open Data download page – link below – and
download the following datasets
https://www.ordnancesurvey.co.uk/opendatadownload/products.
html
2. The first step involves selecting all the data you want to
download, so do the things below first.
· Scroll down and tick the box to download the OS VectorMap
District vector layer for the SK National Grid Reference square.
You can select an individual tile by clicking on the relevant
square in the image or by selecting it from the list.
· Then tick the box to download the OS VectorMap District
raster layer for the SK National Grid Reference square.
Tip:
· The OS VectorMap vector layer is useful if you want to select
elements from it e.g. to only display buildings and roads.
· The OS VectorMap raster layer is a good option if you just
want a basemap image.
· Then, tick the box to download the Boundary-Line layer. This
is a vector layer and is about 340mb in size.
· Make sure you click the ‘Download’ box (the one to the right)
rather than the DVD. If you select DVD they will send you a
DVD but that’s no good for today!
· Once you’ve selected the data you need, scroll to the bottom
of the screen and click ‘Continue’
· At the next step you’ll have to add some information. You’ll
need to enter your e-mail address (where you want the download
link to be sent to) and market sector (you can put ‘public sector’
here) and then for Company Name you can just say ‘University
55. of Sheffield’ – all other information is optional.
· You then have to add in the little CAPTCHA code in the
bottom left before you can click ‘Continue’. Once you do this
you’ll see a ‘thank you’ screen and an order ID.
· Soon after this you’ll receive an e-mail with 3 download links
– when you do, download the data to your external hard drive –
it should only take about 5 minutes at the most.
If you’ve followed the above steps correctly, here is what you
should have in your folder:
· Now you just need to unzip these files to your external hard
drive. When you do, take a look inside the folders and you’ll
see that there are lots of layers! Don’t add anything to QGIS
just yet.
Before we go any further, I want you to download the
cartographic style sheets for QGIS that we’ll use later on. These
files allow us to use styling consistent with that used by the OS
(we can also save or own styles). Follow the simple steps
below.
· Go to the web link below
https://github.com/OrdnanceSurvey/OS-VectorMap-District-
stylesheets; then click the green ‘Clone or Download’ button.
· Select the ‘Download Zip’ option.
· Once you’ve downloaded the folder, unzip it and look inside
it. The stylesheets you need can be found by following this file
path:
…OS-VectorMap-District-stylesheets-masterOS-VectorMap-
District-stylesheets-masterESRI Shapefile stylesheetsQGIS
stylesheets (QML)
56. What is a QML file?
The QML file (.qml) contains: Style information
The QML (.qml) file in QGIS is a style file. It contains an
export of the style information, including labels, from a layer.
The .qml file however has no reference to the layer. This means
I can share a .qml file with you and you can apply it to your
own data without needing the data I exported it from. QML files
are handy if you have one, or more, layers but have a collection
of different style that you want to apply to them.
(from https://nathanw.net/2014/03/22/all-the-q-files/)
Task 2:
Now I want you to add the following shapefile layers from the
OSVectorMapExtract folder to QGIS:
1.
14
· SK_Building
· SK_NamedPlace
· SK_RailwayStation
· SK_RailwayTrack
· SK_RailwayTunnel
· SK_Road
· SK_SurfaceWater_Area
· SK_SurfaceWater_Line
· SK_Woodland
These are some of the individual layers that go to make up the
57. OSVectorMap the name should give you an indication of what
they contain! As you can see form the QGIS canvas window, it
is quite hard to make out what is going on. By applying
different styles to the different layers we can make this look
much better. First, however, we are interested in just the area
around Sheffield and this is only a small part of the area in the
SK data. The next few steps are going to walk you through the
process of clipping the layers so that we only show our area of
interest.
Task 3: Dissolve the boundary line layer
The next thing I want you to do is to create an outline boundary
layer for Sheffield. We are going to use the Dissolve tool to
create a boundary layer for Sheffield – like the one shown on
page 3 of the workbook. We could of course just use a ready-
made Sheffield layer but I want to show you how to create a
boundary out of smaller shapes when you don’t have one. This
is a really useful GIS skill to learn. I have done the first steps
below for you, this is in the BoundarySheffieldWard.zip file.
· Navigate to the folder with the Boundary-Line data in it –
that’s the one called bdline_essh_gb, this dataset contains a
number of shapefiles for different administrative boundaries and
can be very useful. Now add the following layer from the Data
folder: district_borough_unitary_ward_region.shp .
· This covers most of Great Britain but if you open the attribute
table you’ll see that there is a field called FILE_NAME which
you can use to dissolve the layer to create a new shape for
Sheffield.
· First of all, Filter the layer so that only Sheffield is showing (
right click layer, select Filter… and then type in the expression
"FILE_NAME" = 'SHEFFIELD_DISTRICT_(B)'). You should
see that although it is the outline of Sheffield, it is made up of
lots of smaller areas. We are going to use this to make a layer
with a single feature showing only the outline of Sheffield.
58. · Add the BoundarySheffieldWard.shp file. You should see
Sheffield and the ward boundaries within it. We are going to
‘dissolve’ this dataset so that is only one feature – Sheffield.
· You may want to ‘turn off’ the other layers at this point (all of
those starting with ‘SK_’ as re-drawing them can cause your
computer to run more slowly.
· Now you need to go to Vector >> Geoprocessing Tools >>
Dissolve (you can also find this by searching in the Processing
Toolbox). Make sure your settings look like the image below
and then click OK. It should only take a few seconds to add the
new boundary to the map – then save your QGIS project.
Task 4: Create a buffer around Sheffield
Great work so far! As mentioned, the SK data covers a much
larger area than we actually need. This means QGIS is drawing
and re-drawing much more data than it needs to and it can slow
down the mapping process. We are now create a buffer around
the Sheffield boundary, we are then going to use this buffered
layer to clip the other SK layers to a more manageable area.
· Using the dissolved Sheffield boundary layer from the
previous step, go to Vector >> Geoprocessing Tools >>
Buffer(s) and make sure your settings are the same as the image
below, then click OK.
The new buffered layer can now be used to clip the layers we
added earlier on.
· Although we’re just doing this to reduce our shapefile size,
you can use buffers in a wide variety of contexts in GIS – e.g.
to identify the extent of territorial waters along a coastline, to
identify areas within a certain distance of a motorway, to
identify how many people live within a distance of a particular
point, and so on. Always keep in mind the other uses for
59. geoprocessing tools.
Task 5: Clip your SK layers
Now that you’ve got an extended Sheffield boundary from the
buffer procedure above, I want you to use it to clip all the SK
layers you created previously. Just follow the instructions below
to do this.
· Go to Vector >> Geoprocessing Tools >> Clip and make sure
your settings match my example below – the input vector layer
should be the layer you want to clip (i.e. SK_Building,
SK_NamedPlace etc.) and the clip layer should be the new
Sheffield buffered layer. Once you click OK it will take a little
while to process before it is added to the map canvas.
· You should repeat the process so that you have clipped all 9
layers. To make the next steps easier, I recommend you name
the new clipped files as shown in the table below:
Original layer name
New ‘Clipped’ name
· SK_Building
· Building
· SK_NamedPlace
· NamedPlace
· SK_RailwayStation
· RailwayStation
· SK_RailwayTrack
· RailwayTrack
· SK_RailwayTunnel
· RailwayTunnel
· SK_Road
· Road
· SK_SurfaceWater_Area
· SurfaceWater_Area
· SK_SurfaceWater_Line
60. · SurfaceWater_Line
· As you can see below, the clipped versions have much smaller
file sizes and this will make things much easier for us.
Task 6: Putting it all together in a map
The task now is to put all this data together in a map, styled
using Ordnance Survey’s QGIS layer stylesheets. This will
make your map look beautiful and with a little extra bit of
trickery you can add a nice glowing buffer around Sheffield so
that it highlights the city boundary and darkens everything else.
These are the files we downloaded earlier and should be in a
folder called ‘OS-VectorMap-District-stylesheets-master’.
· Make sure you have the following clipped files in your QGIS
window:
· Building
· NamedPlace
· RailwayStation
· RailwayTrack
· RailwayTunnel
· Road
· SurfaceWater_Area
· SurfaceWater_Line
· Woodland
· You should now make sure that the only layers you have in
QGIS are the new SK clipped layers listed above (there should
be 9 of these) AND plus the Sheffield boundary layer you
created using the Dissolve process (NOT the buffered layer).
You can remove any other layers because it may get confusing.
The next step is to style the layer using the Ordnance Survey
stylesheets we’ve already downloaded. Ordnance Survey maps
are very carefully created by expert cartographers and are easily
recognisable to many people. We can use the stylesheets they
provide to create maps that use the same symbology and styling.
61. To recreate their styles, we first need to make sure our layers
are in the correct order in the Layers panel. They provide an
image (shown left) so you know what order they should be in.
This file is VMD_layer_order.png file in the Images folder
Make sure your 9 layers (indicated by the red boxes in this
image) are in the order indicated.
Next, go to the properties for each layer in your map and in the
Style properties, click ‘Load Style’ in the bottom left.
Then navigate to the qml stylesheet for that layer – e.g. the
correct style for the Building layer is called Building.qml (as
you can see below). Once you’ve done this you can click OK
and you’ll see that the map style changes. Make sure you follow
the path below and use the files within the ‘ESRI Shapefile
stylesheets’ folder
‘…OS-VectorMap-District-stylesheets-masterOS-VectorMap-
District-stylesheets-masterESRI Shapefile stylesheetsQGIS
stylesheets (QML)Full Color Style’
· Note that the latest OS style sheets have multiple styles for
roads. These allow for details including overpasses and
complicated intersections. For most maps we won’t so much
detail so we can use only the Level 0 sytles. To do this first
duplicate your clipped road layer (right click on the layer name
and select duplicate). Then select the Level – 0 (Casings) and
Level -0 (Fill) files for the two road layers in that order.
· Once you’ve styled the layers, you’ll have to make sure that
they are in the right order and that some layers are not
obscuring others – e.g. if you have the RailwayTrack layer over
the Road layer in Sheffield then you won’t see the tram routes
on the streets. The folder you downloaded containing the styles
62. also contains a folder called ‘images’; in here is an example
output and a screenshot showing the correct layer order to help
you organise your layers.
· See the image below for an example of how it should look.
Zoom in to different areas in the map to see how it looks.
You’ll notice that the qml stylesheets sort out all sorts of
things.
· Once you have your map the way you want it, start a new Print
Layout (press CTRL + P), give it a name (e.g. Sheffield A0
Map), and then add the map to the layout.
· I want you to create an A0 size Landscape orientation map of
Sheffield. On the next page I have shown you the settings I
used, so please follow them to achieve the same look.
These are the settings I used in the Page Setup box from the
Layout menu in Print Layout:
You can use the Sheffield outline layer to create a nice
boundary effect (as seen on the front cover). These are the
settings I used to achieve the green glow for the Sheffield
boundary – black may look better, but you can experiment
yourself.
· Check that the Sheffield boundary layer is on the top to make
sure you get the correct effect.
· When you’re happy with it, go to Layout, Export as Image and
save the file as a png. It will take a few minutes and produce a
massive file. Click OK if it gives you a memory warning at this
point.
63. Styling comments and tips
The purpose of the second part of today’s session was to get
you to understand some basic geoprocessing tools in QGIS and
to help you produce a nice looking map of Sheffield with the
results. However, you don’t need to merge, clip, buffer or
dissolve any data to produce a nice map with Ordnance Survey
data – it’s just that it can significantly improve map quality and
reduce data volume if you do. The final few bullet points offer
some comments and tips for you.
· If your qml files have the same name as a shapefile- and are in
the same folder - then the styling will be automatically applied
when you add the shapefile to QGIS.
· To save time, you could omit the buffer and clip process and
just skip straight to styling the layers and setting up the map in
the Print Composer. But if you only want to map a small area
then it can be really tiresome waiting for the map to redraw
massive shapefiles. And of course the point of today was about
geoprocessing techniques.
· Why not create a beautiful wall map of your home town? You
can really get creative here once you’ve got the method nailed
down.
· When you’ve got the Inverted Polygon style on and you’re
using the Shapeburst fill to create a glow effect around a
polygon, you can set the second colour to Transparent. This will
fade the colour from your chosen colour transparent so that the
surrounding areas are not dimmed.
· You can also create your own ‘style’ files. Once you have
symbolised a layer, select the ‘Save style’ option from the drop
down ‘Style’ box at the bottom of the Symbology box. You can
then re-use this symbology by simply loading as we did above.
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