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Basics of Imaging systems

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Basics of Imaging systems Lecture 1 prepared by Rick Lathrop 8/02 The remote sensing process Acquisition and analysis Reading this viewgraph eyes acquire the data ... – PowerPoint PPT presentation

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Title: Basics of Imaging systems


1
Basics of Imaging systems
  • Lecture 1
  • prepared by Rick Lathrop 8/02

2
Basics of Imaging Systems Remote Sensing
Remote sensing is the science and art of
obtaining information about an object, area, or
phenomenon through the analysis of data acquired
by a device that is not in contact with the
object, area, or phenomenon under
investigation.- Lillesand Kiefer (1987)
Alternative term Digital Image Analysis
3
The remote sensing process
  • Acquisition and analysis
  • Reading this viewgraph
  • eyes acquire the data, the brain processes it
    into information (I hope)
  • Aerial photography-the traditional means of
    remote sensing
  • Camera captures data with a lens system and
    chemical reactions on light sensitive films
  • Print is the storage and presentation media-eyes
    and brain process the data into useful information

4
Remote Sensing Model
  • Remote sensing systems record reflected and/or
    emitted electromagnetic energy (i.e. light) as a
    2D image.
  • Of critical interest is how earth surface
    features (i.e. the target) interact and affect
    the reflected and/or emitted energy

5
The visible spectrum
  • The visible spectrum is only a tiny window
  • We are blind to 99.99 of the energy in the
    universe
  • One of the strengths of remote sensing is that we
    have created devices that allow us to see beyond
    the range of human vision

6
The electromagnetic spectrum
7
Framing systems Instantaneously acquire an image
  • Analog Camera - uses a lens to form an image at
    the focal plane. A shutter opens at selected
    intervals to allow light to enter, where the
    image is recorded on photographic film or an
    array of detectors
  • Digital Camera - type of camera that records an
    image on an 2D array of photosensitive detectors
    that is then recorded as a digital image file

8
Aerial photos
  • The traditional form of remote sensing
  • Pro
  • Can be easily customized to meet specific
    requirements
  • Historical archive
  • Con
  • Can be expensive
  • Need access to plane
  • Visual interpretation Time consuming
  • Repeat coverage often infrequent
  • Different sun angles

9
Aerial photos Film Types
  • Black White panchromatic (Visible)
  • Black White Infrared Near Infrared
  • Color Visible Blue, Green, Red
  • Color Infrared Visible to Near Infrared

10
Primary Colors
Red
Green
Blue
11
Subtractive Primary Colors
Yellow (RG) absence of blue
Cyan (GB) absence of red
Magenta (RB) absence of green
12
Color Additive Process
R
Y
G
W
C
M
Black background
B
13
Color Subtractive Process
G
Y
C
B
B
R
M
White background
14
Color film
Original colors
G
R
B
Y
M
C
Dye Layers
B
G
R
Film Image colors
15
Color Infrared film
Original colors
G
R
NIR
B
Filter
Dye Layers
Y
M
C
B
G
R
Film Image colors
16
Fundamental Recognition Elements
  • Shape
  • Size
  • Shadows - shape height
  • Tone/Color
  • Texture
  • Pattern
  • Site
  • Association

17
Photointerpretation Recognition Elements
  • Shape
  • cultural features - geometric, distinct
    boundaries
  • natural features - irregular shapes and
    boundaries
  • Shape helps us distinguish old vs. new
    subdivisions, some tree species, athletic fields,
    etc.

18
Photointerpretation Recognition Elements
  • Size
  • relative size is an important clue
  • apartments vs. houses
  • single lane road vs. multilane

19
Photointerpretation Recognition Elements
  • Shadows
  • shadows cast by some features can aid in their
    i.d.
  • some tree types, storage tanks, bridges can be
    identified in this way
  • shadows can also accentuate terrain

Powerline transmission towers
20
Photointerpretation Recognition Elements
  • Color/Tone
  • irrigated vs. dry fields, coniferous vs.
    deciduous trees

An algae bloom in color
An algae bloom in CIR
21
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22
Photointerpretation Recognition Elements
  • Texture
  • coarseness/smoothness caused by variability or
    uniformity of image tone or color
  • smoothness - surface features of similar height
    crops, bare fields, water, etc.
  • coarseness - irregular surface forest, lava flows

Helyar Woods and points south
23
Photointerpretation Recognition Elements
  • Pattern
  • overall spatial form of related features
  • repeating simple geometric patterns tend to
    indicate cultural features
  • more complex, curving patterns tend to indicate
    natural features
  • drainage patterns can help geologists determine
    bedrock type

A dendritic pattern is characteristic of
flat-lying sedimentary bedrock
24
Photointerpretation Recognition Elements
  • Site
  • site - relationship of a feature to its
    environment/location
  • oak on hillside, Atlantic. white cedar in stream
    corridor
  • Association
  • identifying one feature can help i.d. another -
    correlation
  • cooling towers, HT lines gt power generating
    plant
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