Lesson 306 Satellite Imagery Theory

Question 1

List the two types of satellite systems

Answer 1

Geostationary (GEOS)
Polar orbiting (POES)

Question 2

Name the two types of radiation measured by satellite sensors

Answer 2

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)

Question 3

Define sensor resolution

Answer 3

The smallest area that can be distinguished from surrounding areas by the satellite sensor.

Question 4

Define image resolution

Answer 4

The smallest area that can be distinguished from the surrounding areas on a satellite image.

Question 5

What are the advantages and disadvantages for the GOES satellite?

Answer 5

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.

Question 6

What are the advantages and disadvantages of the POES satellite?

Answer 6

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.

Question 7

List the four spectral bands used by Nav Canada

Answer 7

Visible (VIS)
Water vapour (WV)
Infrared (IR)
Near Infrared (NIR)

Question 8

List the typical albedo values used on infrared imagery

Answer 8

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%.

Question 9

What is the major advantage of the IR image over the VIS image?

Answer 9

Because cloud top temperature decreases with height, IR images show good contrast between clouds at different levels.

Question 10

Clouds with a high albedo have:

LHS

Answer 10

Large vertical depth
High cloud-water content
Small average cloud-droplet size

Question 11

Clouds with a low albedo have:

SLL

Answer 11

Shallow depth
Low cloud-water content
Large average cloud-droplet size

Question 12

List the problem areas in interpreting VIS imagery

DST

Answer 12

Distinguishing clouds from snow covered ground
Small clouds
Thin clouds

Question 13

How many tones of grey are used on the grey scale?

Answer 13

Up to 256 shades of grey. The human eye can only perceive 15-40 tones.

Question 14

Why do we enhance satellite imagery?

Answer 14

In order to more easily identify phenomena of interest.