Cells - Absolute Values

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Cells - Absolute Values

• In this instance, the value of the cell
  represents the value of the phenomenon of
  interest, e.g. the elevation at that pixel
  location.

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Flood Assessment
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General Classification of Scale

• Remember that the notions of small and large are
  reversed from our conventional thinking when we
  talk about scale ? large scale refers to looking
  at a smaller area in detail.
• Here are some scale guidelines
• Large scale ? 1400 to 150,000
• Intermediate scale ? 150,000 to 1250,000
• Small scale ? 1250,000 and beyond

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UTM Zone Projection
Central meridian
Standard lines
Transverse Mercator Projection applied to each
6o zone to minimize distortion
Transverse Mercator A cylindrical projection
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Geodetic Datums
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Digital Image Processing Image Enhancement
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Contrast Enhancement example

• A linear stretch is one of the most common types
  of contrast enhancement
• Minimum BV is remapped to 0
• Maximum BV is remapped to 255

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The sky is blue because of Rayleigh Scattering.
Shorter wavelengths (i.e. blue) of the visible
spectrum are scattered more than longer visible
wavelengths. So why isnt the sky indigo or
violet?
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Rayleigh Scattering

• Short wavelengths are scattered by this mechanism
  more than long wavelengths.

R O Y G B
I V
Short ?
Long ?
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Vector data

• County borders within a state

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Raster Data Model - Points
1 point 1 cell

• What problems do we have here?
• 2 points in a pixel
• Point on a border

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• Detecting Stress In CropsContinuous features
  vector or raster?

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Shape

• Differences in forms of symbols
• Options
• abstract (e.g circle, square)
• iconographic (e.g. airplane, flag, schoolhouse)
• Caution too many different shapes can get very
  busy and difficult for the map reader to
  discriminate

Utility
Ordinal Ratio Nominal
Bad ? Bad ? Good ?
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Rules for Assigning Cell Values

• Cell values can be assigned to cells accorded to
  some set of rules, and selecting those rules
  differently can also effect the representation of
  features

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Satellite Imagery

• Described by five resolutions
• Spatial resolution area on ground represented by
  each pixel
• Advanced Very High Resolution Radiometer (AVHRR)
  1 km
• Landsat - 30m
• SPOT 2.5m - 20m / 2.5m - 10m
• IKONOS - 1m/4m
• Temporal resolution how often a satellite
  obtains imagery of a particular area
• Spectral resolution specific wavelength
  intervals in the electromagnetic spectrum
  captured by each sensor
• Radiometric Resolution number of possible data
  values reportable by each sensor (how sensitive
  the sensor is to changes in brightness of objects
  that it views)
• View angle resolution the number of angles at
  which the ground objects are recorded by the
  sensor.

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Question 23

• In the following diagram of vector data, what is
  the Right polygon for arc 8?
• A
• B
• C
• D
• E

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Question 24

• Which 2 bands are most crucial to differentiate
  between Red Sand and Pinewoods?
• Bands 1 and 2.
• Bands 1 and 4.
• Bands 2 and 5.
• Bands 3 and 4.