Remote Sensing and Image Interpretation

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Remote Sensing and Image Interpretation

• Speaker
• Shagufta Akbari
• Assistant Prof.
• KL University

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contents

• Introduction
• Map as a model
• Spatial elements and terminology
• Classification of Maps
• Map Scale
• Spatial referencing system
• Computers in map production
• General softwares in map production
• Types of data products

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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

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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 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.

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Classification of Maps

• On the basis of scale
• Small scale map
• Large scale map- urban plan map, transportation
  and network map

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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

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• In India commonly used fractional map scales are
  11,00,000,00 1250,000, 150,000 125,000 and
  110,000
• 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

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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
  earths 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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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

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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

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General softwares in map production

• Arc- GIS
• ARC- VIEW etc.

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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
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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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Levels of interpretation keys

• Interpretation Keys Criterion for identification
  of an object with interpretation elements

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Basic elements of image interpretation
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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

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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

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Shadow

• Shadow usually a visual obstacle for image
  interpretation
• Gives height information about towers, tall
  buildings

H object
S Shadow
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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

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• 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