Remote Sensing
and Image
Interpretation
By: Lokender Yadav

contents
 Introduction
 Map as a model
 Spatial elements and terminology
 Classification of Maps
 Map Scale
 Spatial referencing system
 Computers in map production
 General software’s in map production
 Types of data products

Continued ……Continued ……
 Image interpretation strategy
 Levels of interpretation keys
 Topography
 Types of Drainage pattern and Texture
 Erosion
 Process of image interpretation
 Basic elements of image interpretation
 Overview on visual image interpretation equipment

 Map as Model
 Representation of features of earth drawn to scale
 “A map is a very powerful tool and maps are typical
reductions which are smaller than the areas they portray”
(Robinson et.al 1984)

Spatial elements and terminology
 Spatial objects in the real world can be thought of as occurring in
four easily identifiable types namely, points, lines, areas and
surfaces
 Points, lines and areas can be represented by using symbols to
depict the real world.
 Surfaces are represented by any combination of these spatial
entities.
 In general, all the geographic surfaces are in two tangible forms,
namely, discrete and continuous.

 Trees, houses, road intersections and similar items are discrete
spatial features.

Classification of Maps
 On the basis of scale
 Small scale map
 Large scale map- urban plan map, transportation and
network map

Map Scale
 The ratio between the reduced depiction on the map
and the geographical features in the real world is
known as the Map Scale
 Scale expressed in three ways:
◦ Fractional scale-the method of representing this type of
scale is called representation fraction method

 In India commonly used fractional map scales
are 1:1,00,000,00; 1:250,000, 1:50,000;
1:25,000 and 1:10,000
 Graphical Scale- A line printed on the map and
divided into units that are equivalent to some
distance
 The measured ground distance appears directly
on the map in graphical representation
 Verbal Scale- This is an expression in common
speech like “an inch to a mile”

Spatial referencing system
 To locate objects with respect to some reference system
 Methods of spatial referencing systems
◦ Geographic coordinate systems-
 Denoted by latitude and longitude
◦ Rectangular coordinate systems(RCS)
 Spatial data are in two-dimensional form
 Relative position- location of any point on the earth’s surface w.r.t RCS
◦ Non- coordinate systems
 Spatial reference with descriptive codes such as postal codes which is
numeric in nature

Computers in map production
 Advantages
 To make existing maps more at a quicker pace
 To make existing maps at a cheaper rate
 To make maps for specific user needs
 To make map production possible in situations where skilled
staff are unavailable
 To allow experimentation with different graphical
representations of the same data

Continued…
 To facilitate map making and updating when the data are already in digital
form
 To minimize the use of the printed map as a data store and thereby to
minimize the effects of classification and generalization on the quality of
the data
 Introduction of automation can lead to a review of the whole map –
making process , which can also lead to savings and improvements

General software’s in map production
 Arc- GIS
 ARC- VIEW etc.

Types of data products
Depending on correction applied &
level of processing
Note: FCC are generated by combininig the data contained in three spectral bands
respectively. The choice of band combinations can be determined depending
upon application

Image interpretation strategy
Visual image interpretation : Process of indentifying
what we see on the images and communicate the
information obtained from these images to others for
evaluating its significance
Includes relative locations and extents
Use of data products like Satellite single band
imageries, FCC for performing image interpretations
to extract thematic information for subsequent input
to GIS

Levels of interpretation keys
 Interpretation Keys: Criterion for identification of an
object with interpretation elements

Basic elements of image interpretation

Size
 Size of objects in an image is a function of scale
 Proper photo scale selected depending on the purpose
of interpretation
 Most commonly measured parameters:- length, width,
perimeter, area and occasionally volume

Shape
 Shape of an object is described as the geometric form
represented form represented on an image
 Regular shapes are signs of man-made objects
 Irregular shapes with no distinct geometrical pattern
are signs of a natural environment

Shadow
 Shadow – usually a visual obstacle for image
interpretation
 Gives height information about towers, tall buildings
H
object
S
Shadow
θ
tan
H
S
θ =

Tone
 Band of EM spectrum recorded by RS system may be
displayed in shades of grey ranging from black to white
 Tone:-
 continuous grey scale varying from white to black
 It refers to relative brightness or colour of objects in an
image
Note:- Humans differentiate 40- 50 individual shades of grey
RS image

 Colour
 more convenient for the identification of object details
 Texture
 Characteristics placement & arrangement of repetitions of
tone or colour in an image
 Visual impression of roughness or smoothness of an image
region

Thank you!!!