Transcript Remote Sensing and Image Interpretation

Speaker
Shagufta Akbari
Assistant Prof.
KL University
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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
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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
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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)
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Spatial objects in the real world can be thought of as
occurring in four easily identifiable types namely, points,
lines, areas and surfaces
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Points, lines and areas can be represented by using
symbols to depict the real world.
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Surfaces are represented by any combination of these
spatial entities.
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In general, all the geographic surfaces are in two tangible
forms, namely, discrete and continuous.
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Trees, houses, road intersections and similar items are
discrete spatial features.
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On the basis of scale
◦ Small scale map
◦ Large scale map- urban plan map, transportation
and network map
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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
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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
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Verbal Scale- This is an expression in common speech like “an
inch to a mile”
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To locate objects with respect to some reference
system
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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
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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
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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
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Arc- GIS
ARC- VIEW etc.
Types of data products
Depending on correction applied &
level of processing
RS data products
Photographic products such as paper
prints, film negatives, diapositives of
black and white and FCC False color
composite
Digital form CCTs
computer compatible
tapes
RS data products
Raw data: radiometrically and
geometrically uncorrected
data
Standard data: radiometrically
and geometrically corrected
data
Geocoded products:data: products are north
oriented and compatible to survey of India
mapsheet
Precision product: radiometrically and
geometrically corrected data with the use
of GCP to achieve greater locational accuracy
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
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Interpretation Keys: Criterion for
identification of an object with interpretation
elements
X, Y location
size
shape
shadow
Basic elements
of image
interpretation
Tone
colour
Texture
Pattern
Height & Depth
Site, Situation & Association
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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
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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
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Shadow – usually a visual obstacle for image
interpretation
Gives height information about towers, tall
buildings
H
object
tan  
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S
Shadow
H
S
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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
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Colour
◦ more convenient for the identification of object
details
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Texture
◦ Characteristics placement & arrangement of
repetitions of tone or colour in an image
◦ Visual impression of roughness or smoothness of
an image region