Types of curves and introduction of GIS

1. Surveyingand Applicationof GIS in Civil
Technology
Lecture1 &2
 By Engr.UMAR ZAHID

2. What is GIS
A geographic information system or
(GIS) is a system designed to capture,
store, manipulate, analyse, manage,
and present all types of spatial or
geographical data

3. Topography map
In modern mapping, a topographic map is a
type of map characterized by large-scale
detail and quantitative representation of
relief, usually using contour lines, but
historically using a variety of methods.
Traditional definitions require a
topographic map to show both natural and
man-made features.

4. Mapping on GIS
Mapping and GIS applications allow to capture,
store, manipulate, analyse, manage, and present
all types of geographically referenced data. GIS
technology combines database, mapping and
statistical methods to integrate geo referenced
data into visual displays where the relationships,
patterns and trends in the data can be more easily
identified.
GIS technologies to be more generally used.

6. Curves:-
Curves are provided whenever a road changes its direction
from right to left (vice versa) or changes its alignment from up to
down (vice versa). Curves are a critical! element in the pavement
design. They are provided with a maximum speed limit that should
lie followed very strictly. Following the speed limit becomes
essential as the exceed in speed may lead to the chances of the
vehicle becoming out of control while negotiating a turn and thus
increase the odds of fatal accidents. Also, it is very necessary that
appropriate safety measures be adopted at all horizontal and
vertical curves to make the infrastructure road user friendly and
decrease the risks of hazardous circumstances.
Types of Curves
There are two types of curves provided primarily for the comfort
and ease of the motorists in the road namely:
Horizontal Curve
Vertical Curve

7. Horizontal Curves
Horizontal curves are provided
to change the direction or alignment of a
road. Horizontal Curve are circular curves or
circular arcs. The sharpness of a curve
increases as the radius is decrease which
makes it risky and dangerous. The main
design criterion of a horizontal curve is the
provision of an adequate safe stopping sight
distance

8. Types of Horizontal Curve:
Simple Curve:
A simple arc provided in the road to impose a curve between the
two straight lines.

9. Compound Curve:
Combination of two simple curves combined together to curve in
the same direction.

10. Reverse Curve:
In civil engineering, a reverse curve (or "S" curve) is a section of the
horizontal alignment of a highway or railroad route in which
a curve to the left or right is followed immediately by a curve in the
opposite direction.

11. Transition or Spiral Curve:
A curve that has a varying radius. Its provided with a simple curve
and between the simple curves in a compound curve.
While turning a vehicle is exposed to two forces. The first force
which attracts the vehicle towards the ground is gravity. The second
is centripetal force, which is an external force required to keep the
vehicle on a curved path. At any velocity, the centripetal force
would be greater for a tighter turn (smaller radius) than a broader
one (larger radius). Thus, the vehicle would have to make a very
wide circle in order to negotiate a turn
This issue is encountered when providing horizontal curves by
designing roads that are tilted at a slight angle thus providing ease
and comfort to the driver while turning. This phenomenon is
defined as super elevation, which is the amount of rise seen on a
given cross-section of a turning road, it is otherwise known as
slope.

13. Vertical Curves
Vertical curves are provided to change the slope in the road and
may or may not. be symmetrical. They are parabolic and not
circular like horizontal curves. Identifying the proper grade and
the safe passing sight distance is the main design criterion of the
vertical curve, in crest vertical curve the length should be
enough to provide safe stopping sight distance and in sag
vertical curve the length is important as it influences the factors
such as headlight sight distance, rider comfort and drainage
requirements.
Types of Vertical Curve:
Sag Curve:
Sag Curves are those which change the alignment of the road
from uphill to downhill.
Crest Curve/Summit Curve:
Crest Curves are those which change the alignment of the road
from downhill to uphill. In designing crest vertical curves it is
important that the grades be not] too high which makes it
difficult for the motorists to travel upon it.

15. Discharge
Discharge is the volume of water moving down a stream or river per unit of
time, commonly expressed in cubic feet per second or gallons per day. In
general, river discharge is computed by multiplying the area of water in a
channel cross section by the average velocity of the water in that cross section:
Current Meter
The most common method used by the USGS for measuring discharge is the
mechanical current-meter method. In this method, the stream channel cross
section is divided into numerous vertical subsections. In each subsection, the
area is obtained by measuring the width and depth of the subsection, and the
water velocity is determined using a current meter . The discharge in each
subsection is computed by multiplying the subsection area by the measured
velocity. The total discharge is then computed by summing the discharge of
each subsection.

16. Numerous types of equipment and methods are used by USGS personnel
to make current-meter measurements because of the wide range of
stream conditions throughout the United States. Subsection width is
generally measured using a cable, steel tape, or similar piece of
equipment. Subsection depth is measured using a wading rod, if
conditions permit, or by suspending a sounding weight from a calibrated
cable and reel system off a bridge or boat .
The velocity of the stream flow is measured using a current meter. The
most common current meter used by the USGS is the Price AA current
meter. The Price AA current meter has a wheel of six metal cups that
revolve around a vertical axis. An electronic signal is transmitted by the
meter on each revolution allowing the revolutions to be counted and
timed. Because the rate at which the cups revolve is directly related to the
velocity of the water, the timed revolutions are used to determine the
water velocity. The Price AA meter is designed to be attached to a wading
rod for measuring in shallow waters or to be mounted just above a weight
suspended from a cable and reel system for measuring in fast or deep water.

18. Question 1
A reservoir has the following areas by contours at various elevation. Determine
the
Elevation
(m)
200 220 240 260 280 300
Area of
contours
(km2)
150 175 210 270 320 400

19. Solution by cone method
Elevation
interval(m)
Area(km2) Equation Volume in km2-m
200 150 20/3*(150+175+(150*175)^1/2) 3246.79
220 175
220 175 20/3*(175+210+(175*210)^1/2 3844.69
240 210
240 210 20/3*(210+270+(210*270)^1/2 4787.45
260 270
260 270 20/3*(270+320+(270*320)^1/2 5892.93
280 320
280 320 20/3*(320+400+(320*400)^1/2 7185.14
300 400
Total storage volume 24975