thermal images

Question 1

what part of the EM spectrum does thermal remote sensing sense

Answer 1

in infrared region

Question 2

wavelength range of thermal remote sensing

Answer 2

3-5 microns in middle infrared region
8-14 microns in thermal infrared region

Question 3

what is the main factor in thermal remote sensing

Answer 3

surface temperature

Question 4

how does thermal remote sensing vary?

Answer 4

seasonally, by location and exposure to solar irradiation

Question 5

what does thermal remote sensing measure

Answer 5

emitted energy (thermal)

Question 6

when can thermal remote sensing be done

Answer 6

no restrictions even at night time

Question 7

how is thermal remote sensing different from reflected light imagery

Answer 7

• main factor: surface temp
• measures emitted energy
• can be performed at night
• varies seasonally, depending on location and exposure to irradiance

Question 8

when energy varies, what also varies?

Answer 8

spectral characteristics

Question 9

what is wiens displacement equation

Answer 9

𝜆𝑚 = A/T

𝜆𝑚 = wavelength of maximum spectral radiance exitance in microns
A = 2898 microns
T = temperature in K

Question 10

wavelength at which the blackbody radiation curve reaches a maximum

Answer 10

dominant wavelength

Question 11

Materials that absorb and radiate only a certain fraction compared to a blackbody

Answer 11

greybody

Question 12

radiate only a certain fraction of a blackbody, but this fraction changes with wavelength

Answer 12

selective radiator

Question 13

The fraction of energy that is radiated by a material compared to a true blackbody

Answer 13

emissivity

Question 14

emissivity equation

Answer 14

e𝜆 = M 𝜆,T / M bb𝜆T

emissivity = radiant emittance of a real material in given temp / radiant emittance of a blackbody at the same temp

Question 15

describe the ability of objects to absorb and emit if they reflect well

Answer 15

objects that reflect well would have a poor ability to absorb/emit

Question 16

law that describes the relationship between an object’s absorbance/emittance ability and its reflectance ability

Answer 16

Kirchhoff’s law

Question 17

Kirchhoff’s equation

Answer 17

e𝜆 = 1 - p𝜆

e𝜆 = emissivity
p𝜆 = reflectance
both in given 𝜆

Question 18

what are the 2 objectives for thermal data processing

Answer 18

1. distinguish between surface geologies using emissivity values
2. actual surface temperature needs to be determined

Question 19

highlights the areas where a surface material of interest is predominant

Answer 19

band ratio

Question 20

what is band ratio

Answer 20

radio of two bands near a rapid change in emissivity spectrum of that material

Question 21

what is the low emissivity of sandstone

Answer 21

around 9 microns

Question 22

what is the effect of band ratio to surface temperatures

Answer 22

reduces the influence of differences in surface temperature

Question 23

what is the function of transformations

Answer 23

• minimize the common information
• enhance visibility of differences in the bands

Question 24

in thermal infrared, how do u differentiate rock and soil

Answer 24

they show distinct spectra

Question 25

what are the cause of different spectra (absorption bands) of different soil and rock types

Answer 25

absorption bands are mainly caused by silicate minerals (quartz or felspar)

Question 26

detection and monitoring of small areas with thermal anomalies

Answer 26

thermal hotspot detection

Question 27

what geologic phenomena can be related to thermal hotspot detection

Answer 27

• fires (forest fires or underground coal fires)
• volcanic activity
• lava flows
• geothermal fields