This document provides an overview of remote sensing and image interpretation. It discusses key topics such as the use of maps as models to represent features on Earth, different types of map scales and spatial referencing systems, and how computers are used in map production. It also outlines the process of image interpretation, including levels of interpretation keys and basic elements to examine like size, shape, shadow, tone, color, and texture. Software programs used in map production like ArcGIS and types of data products from remote sensing are also reviewed.

1. Remote Sensing
and Image
Interpretation
By: Lokender Yadav

2. 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

3. 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

4.  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)

5. 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.

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

7. 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

8.  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”

9. 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

10. 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

11. 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

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

13. 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

14. 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

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

16. Basic elements of image interpretation

17. 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

18. 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

19. 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 =

20. 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

21.  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

22. Thank you!!!