Lecture 3

Question 1

Earth observation data can be used for:

Answer 1

1. Mapping
2. Deriving bio geo physical variables
   - change analysis
   - integration with other data
   - monitoring
   - policy and decision making

Question 2

Electromagnetic radiance recorded within IFOV is a function of:

Answer 2

1. wavelength of electromagnetic energy
2. geometry of acquisition
3. surface spectral characteristics

Question 3

What does DN (digital number) represent

Answer 3

the amount of radiance/ brightness value

Question 4

the smallest data set in an image is called:

Answer 4

PIXEL

Question 5

What is the structure of a remotely sensed image? (how do we find DN?)

Answer 5

RS images are stored using a raster representation:
the image is overlaid with a grid:
each box represents the average spectral response for each pixel/band (DN)

Question 6

What is a Band (image structure)

Answer 6

Bands are layers of the spectral data set (raster sets)

Question 7

What is spatial resolution (large vs small)

Answer 7

smallest angular or linear separation between 2 objects that can be solved by the remote sensing system: cell size in raster (IFOV- pixel)

Large cell= low spatial resolution
- course/grain data
- no shadows or geometric issues

Small cell= high spatial resolution
- finer data set= more detail

Question 8

Spectral Resolution

Answer 8

number of and size of specific wavelength’s in the electromagnetic spectrum that the RS system can detect

Question 9

Low spectral resolution VS High spectral resolution

Answer 9

low= entire visible spectrum lumped together
- cannot distinguish red/green/blue
- wider range
- panchromatic

high= finer portions of the spectrum captured
- separate bands ( red, blue or green)
- specific range of spectrum

Question 10

Multispectral data set

Answer 10

composed of several images: each portion of the electromagnetic spectrum
- detects singular bands of the electromagnetic spectrum
- RGB bands

Question 11

Hyperspectral data set

Answer 11

RS system that can detect several very narrow and continuous bands
- very high spectral resolution

Question 12

Radiometric resolution

Answer 12

sensitivity of a RS detector to differences in signal strength as it records the energy reflected from the terrain
- defines the number of discriminable signal levels
- 8-bit data (0-255), 10-bit data (0-1023)
- higher radiometric resolution= higher detail/features

Question 13

Temporal Resolution

Answer 13

amount of time it takes to collect data over the same area
- collected on regular time intervals or by request

image depends on satellites:
- orbit: polar, equatorial geostationary
- swath: narrow or wide
- sensor configuration (continuous/programmed, nadir or side-looking)

Question 14

Wave theory VS Particle theory

Answer 14

Wave theory: structure of radiation = waves
Particle theory: energy content of radiation= particles

Question 15

How is energy is transmitted from the sun to the earth

Answer 15

Emitted: (TIR)
Reflected: (Visible & NIR)

Question 16

Small vs Large Wavelengths (frequency/energy)

Answer 16

small wavelength= high energy= large frequency
Satellites collect data: higher energy= easier to measure

large wavelength= low energy= low energy

Question 17

Radiation Behavior

Answer 17

temperature of object increases = increase total radiant energy
- dominant wavelength shifts towards shorter wavelengths on spectrum

Question 18

What is Atmospheric attenuation? caused by?

Answer 18

Caused by scattering & absorption

Radiation has to pass through atmosphere to reach sensor= attenuation occurs
- short path: airborne sensor (atmosphere
- long path: spaceborne sensor

Question 19

3 types of scattering: what are they/examples of each

Answer 19

1. Rayleigh scattering: gas molecule
   - size of particle smaller than the wavelength of light
   - short wavelengths in upper 4.5km of atmosphere
   most reflective light = blue (sky is blue)
2. Mie Scattering
   - material with diameter approximately the same size of the wavelength
   - dust, smoke, gas
   - energy interacting with larger particles= long wavelengths impacted in lower atmosphere
3. Non-selective scattering ( water vapour)
   - equal amounts of all visible wavelengths are scattering = white appearance
   - particles are 10x greater the size of wavelength
   -Clouds/fog

Question 20

What is absorption

Answer 20

when radiant energy is absorbed and converted into other forms of energy
- efficent absorbers of solar radiation= water vapor, CO2, ozone

Question 21

What is atmospheric windows

Answer 21

portion of spectrum that transmit radiant energy effectively