Elements of Photographic Systems Chapter 2, Remote Sensing and Image Interpretation

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Elements of Photographic SystemsChapter 2,
Remote Sensing and Image Interpretation
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Topics

• Digital Imaging
• Image Capture
• Color Digitization
• Color Corrections
• Image Storage
• Aerial Videography
• Multiband Imaging

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Electronic Imaging(Khosla, 1992)

• Data Capture Photosensitive solid state devices
• Data storage Magnetic, optical, and solid-state
  media
• Data manipulation Digital image processing
• Data transmission Telemetry, telephone lines,
  computer networks
• Softcopy display Computer monitors, television,
  projection video
• Hardcopy display Dye sublimation, inkjet,
  thermal, and laser printers

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Digital (Electronic) Image Fundamentals

• The digital image
• Capture
• Processing
• Storage
• Output

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Image Enhancement
(Kodak)
Multiply or divide each pixel by constant value
Reverse image so black becomes white
Add or subtract constant value
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Analog vs. Digital Curves

• Analog (film) image
• Continuous analog waveform
• Digital image
• Digital values derived from sampling analog image
• Discrete electronic pulses translated into
  strings of zeros and ones

(Kodak)
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Digital Fidelity
(Kodak)
Vertical and horizontal cells sampled at same time
8 bit converter represents 28 256 brightness
levels, 12 bit 212 represents over 4000
Pixel has red level of 227, green level of 166,
and blue level of 97
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The Digital Image (Vector and Raster Graphics)

• Vector (object-oriented) graphics
• Stored as display list giving location and
  properties of objects
• Shapes, arcs, and lines
• Takes a few kilobytes storage
• Raster (bit-mapped) graphics
• Stores location / value of each pixel
• Can take thousands of times more memory than
  vector

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The Digital Image (Vector and Raster Graphics)
(Kodak)
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Image Capture
(Kodak)
Digital image system employs CCD as detector
Basic system is lens film
Pixels created by sensing light intensity of
small portion of film
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Color Digitization
(Kodak)
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Image Quality
(Kodak)
Quality of raster image determined by
spatial resolution and brightness resolution
Pixel resolution determined by rate at which
scanner samples
Brightness or color value of each pixel defined
by one bit or group of bits
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The 24-Bit Pixels
(Kodak)
(16.7 million colors)
(3/ 8-bit sets of numbers)
(one of 256 brightness values for red, green, and
blue)
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Color Corrections
(Kodak)
Reduce green by 50
Reduce red by 50
Reduce blue by 50
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Image Storage
(Kodak)
One 35 mm negative would require 18 megabyte file
Same negative would require 14 high
density floppy disks
120 megabyte hard drive could store six of these
images
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Aerial Videography

• Form of electronic imaging whereby analog or
  digital video signals are recorded on magnetic
  tape or magnetic or optical disks
• Cameras for aerial videography can have many
  configurations
• Single-band
• Multiband
• Multiple single-band
• Cameras can sense in some or all of the
  following
• Visible
• Near-IR
• Mid-IR
• Following configurations are available
• Shuttered cameras--exposure times as short as
  1/10000--used for both analog and digital aerial
  videography
• Analog video recording with 485 horizontal lines
  per image frame
• Digital video recording with horizontal
  resolution of 500 TV lines (TVLs)

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Aerial Videography (Concluded)

• Review of plate 6 (after page 20)
• (a) and (b) are images of cotton field with
  harvester ants
• Spatial resolution of video image (a) lower than
  photograph (b)
• Most of the ant mounds can easily be detected in
  (a)
• (c) and (d) are images of a cotton field with
  saline soils
• Barren to sparsely vegetated saline areas as
  readily distinguished in (c) as in (d)
• Color tones of video composites comparable to
  color IR film tones in both scenes

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Multiband Imaging

• Both normal color and color IR films are
  three-layer systems
• Normal color film layers individually sensitive
  to blue, green, and red energy
• Color IR film--used with appropriate filter-- has
  layers individually sensitive to green, red, and
  near-IR energy
• Three-layer films produce color images because of
  dye layers that control amount of blue, green,
  and red energy that form the final photographic
  image
• Best combination of multiband images for
  discriminating a given scene varies with spectral
  response pattern for objects of interest in the
  scene
• Understanding of object reflectances (and/or
  emittances) and application to multiband imaging
  normally enhances contrast between different
  terrain feature types and between different
  conditions of the same feature type
• Plate 7 (after page 20) shows normal color and
  color IR images that were prepared from
  individual band images shown in table 2.3, pg 122

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Four Views of Crab Nebula from Different
Multispectral Sensing Devices
X-ray
Optical
(rst)
Infrared
Radio
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Supplemental References

• NASA Goddard Remote Sensing Tutorial,
  http//rst.gsfc.nasa.gov/intro/Part2-12.htm
• Lenses The Basics, http//cybercollege.com/typo11
  .htm
• Kodak Digital Learning Center, http//www.kodak.co
  m
• Image Information in the Eye and the Camera,
  http//www.dai.ed.ac.uk/CVonline/LOCAL_COPIES/OWEN
  S/LECT1/node2.htmlSECTION00022100000000000000
• Photogrammetry, http//www.sli.unimelb.edu.au/nico
  le/lectures/lecintro.html