RS Fundamentals

Question 1

Remote sensing

Answer 1

involves the use of instruments or sensors to capture the spectral and spatial relations of objects and materials observable from a distance

Question 2

Components

Answer 2

• Energy source
• Radiation and atmosphere
• Interaction with target (changes nature)
• Energy recorded by sensor
• Transmission, reception, processing
• Interpretation and analysis
• Application of information

Question 3

In RS main types of radiation processes are…

Answer 3

• emission
• reflection
• absorption

Question 4

(ENERGY SOURCE) RS focuses on….

Answer 4

Measurement and information content of EM radiation

Question 5

EM spectrum

Answer 5

-each interval makes up band or channel by:
colour
descriptive label
specified wavelengths

Question 6

RS uses range of EM radiations

Answer 6

0.1 micrometers - 1m

Question 7

UV radtiation

Answer 7

100-400 nm
Shortest wavelength used
-Induced fluorescence in the visible

Question 8

Visible

Answer 8

0.4-0.7 micrometers
-Only visible wavelengths
(RGB)

Question 9

Near Infrared

Answer 9

0. 7-1.2 micrometers
   - Just beyond visible
   - Discriminated Green Vegetation well

Question 10

Mid Infrared

Answer 10

1. 2-8 micrometers

- Between NIR and thermal

Question 11

Short Wave Infrared

Answer 11

1. 2-3 micrometers
   - Detects solar radiation
   - Good for soil and veg moisture

3-8 micrometers

• Solar reflected and surface emitted
• Good for High temp sources

Question 12

Thermal Infrared

Answer 12

8-14 micrometers

-Used to map surface Temp

Question 13

Microwave

Answer 13

Penetrate cloud cover

-Detects Moisture

Question 14

Passive energy source

Answer 14

• reflected energy from sun

- radiation emitted by objects

Question 15

Active energy source

Answer 15

sensor generates own energy

Question 16

Atmospheric interactions

Answer 16

-Interacts with incoming and outgoing EM radiation
-Gases (N, O, CO2, O3) + particles effects:
absorption
reflection & scattering
transmission

Question 17

Atmospheric absorbers

Answer 17

Oxygen - filters UV below 0.1 micrometers
O3 - eliminates UV below 0.3 micrometers
Water vapour - strong absorber ~6 micrometers
CO2 - absorbs in TIR and from 2.5-4.5 micrometers

Question 18

Scattering

Answer 18

redirection of EM radiation from original path due to gas or particles in atmosphere
-amount is dependent on wavelength, amount of particles and distance travelled

Question 19

Rayleigh Scattering

Answer 19

particle &laquo_space;wavelength
shorter wavelength = more scattering
all directions

Question 20

Mie Scattering

Answer 20

particle >= wavelength

still spread out but more in direction of EM travel

Question 21

Non Selective scattering

Answer 21

particle > wavelength

dominantly direction of EM travel

Question 22

At surface radiation…

Answer 22

• is absorbed
• passes through target
• reflects

Question 23

Spectral response

Answer 23

• signature dependent on degree of reflectance
• Texture dependent (in comparison to wavelength)
• smooth = reflection one direction
• rough = all direction

Question 24

Land cover types do not always coincide with spectral reflectance curves due to variability of….

Answer 24

• solar elevation
• slope
• aspect
• atmosphere
• obstructions

Question 25

Spectral reflectance signatures 1. ) snow 2. ) glacier ice 3. ) rock 4. ) water

Answer 25

1. ) snow = high reflectance in visible 2. ) glacier ice = lower in visible and near IR 3. ) rock = high absorption 4. ) water = high absorption

Question 26

Water as target

Answer 26

Long wavelength = absorbed Short wavelength = reflected suspended sediment = better reflectivity

Question 27

Resolution

Answer 27

Ability to discriminate information: - spatial - spectral - radiometric - temporal

Question 28

Spatial Resolution

Answer 28

Min seperation at which objects appears independent and isolated -Expressed a pixel size Eg MODIS - 1km SPOT - 20m IKONOS - 1m

Question 29

When pixel size is smaller (greater spatial resolution)...

Answer 29

Pixel is more likely to be homogenous - closer to original value of target

Question 30

Spectral Resolution

Answer 30

Number of bands provided by sensor and associated spectral bandwidths

Question 31

Radiometric resolution

Answer 31

Indicated sensitivity of a sensor | For digital images the radiometric resolution = range of values coded by sensor

Question 32

Temporal Resolution

Answer 32

Observation frequency - cycle based on certain orbital characteristics and atmospheric conditions Meteorological : 15-20 min Landsat 5-7 : 16 days Radar : 28 days