Flashcards in Lesson 306 Satellite Imagery Theory Deck (14):
List the two types of satellite systems
Polar orbiting (POES)
Name the two types of radiation measured by satellite sensors
Solar - visible shortwave radiation reflected from the earth's surface and the top of clouds (0.2-4 micrometers)
Terrestrial - infrared long wave radiation (3-100 micrometers)
Define sensor resolution
The smallest area that can be distinguished from surrounding areas by the satellite sensor.
Define image resolution
The smallest area that can be distinguished from the surrounding areas on a satellite image.
What are the advantages and disadvantages for the GOES satellite?
GOES: distant, one scan every 15 min., resolution 1km VIS/4km IR/8 km WV, poor resolution N of 60 deg., high cost, 5-7 years life expectancy, solar eclipses affects reception twice per year.
What are the advantages and disadvantages of the POES satellite?
Close to earth (850 km), images produced twice daily, resolution 1 km (always), low cost, 3-5 years life expectancy, solar eclipses have no effect.
List the four spectral bands used by Nav Canada
Water vapour (WV)
Near Infrared (NIR)
List the typical albedo values used on infrared imagery
Clouds 44-95%, fresh snow 85%, desert land 30-40%, land surface 8-40%, grass land 25%, cities 14-18%, forest 9-18%, water 3%.
What is the major advantage of the IR image over the VIS image?
Because cloud top temperature decreases with height, IR images show good contrast between clouds at different levels.
Clouds with a high albedo have:
Large vertical depth
High cloud-water content
Small average cloud-droplet size
Clouds with a low albedo have:
Low cloud-water content
Large average cloud-droplet size
List the problem areas in interpreting VIS imagery
Distinguishing clouds from snow covered ground
How many tones of grey are used on the grey scale?
Up to 256 shades of grey. The human eye can only perceive 15-40 tones.