Satellite Images. Similar idea as aerial photos Similar idea as aerial photos Have some of the same...
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Transcript of Satellite Images. Similar idea as aerial photos Similar idea as aerial photos Have some of the same...
Satellite Images
Satellite Images
Similar idea as aerial photos Have some of the same uses
• Basis for mapping• Image interpretation• Backdrop for map
…but there are some important differences…
How Satellite Images differ from Aerial Images
Have spectral ranges beyond aerial film Very high perspective
• Reduces terrain distortion Cover large areas
• High cost for small area coverage May require specialized image
processing Image acquisition must be scheduled
days or weeks in advance• Follow fixed flight schedules
Lower effective resolution
Basic Principles
Scanners on satellite operate by pointing detectors at area to be imaged• Instantaneous field of view (IFOV) –
corresponds to size of area viewed by each detector
Scanner builds 2D image of surface by recording reflected energy
Ikonos
High-resolution Launched September 1999 1-meter panchromatic infrared 4-meter visible/infrared 13 kilometer swath Revisit times 1-3 days
Landsat
Launched July 1972 First system designed to gather data
about Earth’s land surface Three imaging scanners onboard
• Video camera• Multispectral scanner• Thematic Mapper• Enhanced Thematic Mapper
Revisit time 16-18 days
MODIS
Collects data at range of wavelengths from visible through thermal infrared
Resolution between 250 meters and 1 kilometer
Revisit time 1-2 days at 1 kilometer resolution
Which to use?Satellite or Aerial?
Take the following factors into account• Spatial resolution required• Size of analysis area• Price• Time constraints• Post processing
Mosaicing of Aerials• Spectral requirements• Digital vs Film format