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Fundamentals of remote sensing

Description

First class quiz for Remote Sensing of Global Change, an honours module in the School of GeoSciences, Edinburgh University.
Iain Woodhouse
Quiz by Iain Woodhouse, updated more than 1 year ago
Iain Woodhouse
Created by Iain Woodhouse almost 9 years ago
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Resource summary

Question 1

Question
Which of the following would NOT normally be considered as a form of remote sensing?
Answer
  • Sonar
  • Radar
  • Seismology
  • Ultrasound
  • Gravimetrics
  • None of the above. They are all forms of remote sensing.

Question 2

Question
Electromagnetic radiation can be described completely using wavelength, wave velocity, frequency and amplitude?
Answer
  • True
  • False

Question 3

Question
Label all the key points in this diagram of the temperature profile through the atmosphere. You need to name the zones defined by the temperature changes, the boundaries between them and also label the altitude axis (approximately)
Image:
0bc3794d-2ccc-4c86-a05b-c2e2ea1a7eaf (image/jpeg)
Answer
  • Tropopause
  • Heliopause
  • Thermopause
  • Stratopause
  • Mesopause
  • Troposphere
  • Heliosphere
  • Atmosphere
  • Hydrosphere
  • Stratosphere
  • Mesosphere
  • Thermosphere
  • 20
  • 10
  • 25
  • 40
  • 50
  • 70
  • 60
  • 80

Question 4

Question
Label the different regions of the electromagnetic spectrum.
Image:
dec8bfaf-1371-47fb-a3e8-b8a7c5cd8c5b (image/jpeg)
Answer
  • Visible
  • Gamma rays
  • Optical
  • Electromagnetic
  • Radar
  • Radio
  • Microwave
  • Sonic
  • Seismic
  • Millimetre
  • Sub-millimetre
  • Thermal IR
  • Near Infra-Red
  • Ultra-violet
  • X-rays

Question 5

Question
Label this EM Spectrum with the typical processes that emits radiation of that approximate wavelength.
Image:
6ad9a528-f70f-44c5-9757-b42223cadef0 (image/jpeg)
Answer
  • Molecular transitions (e.g. rotation)
  • High energy molecular transitions
  • Non-ionising electron transitions
  • Ionising electron transitions
  • Thermo nuclear transitions
  • Nuclear transitions

Question 6

Question
Electromagnetic radiation can be created when... (note: there may be more than one answer)
Answer
  • an electron moves from one energy state to a lower energy state.
  • an molecule moves from one kinetic energy state to a lower energy state (e.g. vibration or rotation states).
  • an atomic nucleus changes from one energy state to a lower energy state.
  • an electron moves from one energy state to a higher energy state.
  • an molecule moves from one kinetic energy state to a higher energy state (e.g. vibration or rotation states).
  • an atomic nucleus changes from one energy state to a higher energy state.
  • None of the other answers are correct.

Question 7

Question
Which of the following best describes why a "blackbody" is black?
Answer
  • It is invisible to the naked eye.
  • It completely absorbs all wavelengths of visible light.
  • It completely absorbs all wavelengths of EM radiation, including the ones we can't see.
  • It absorbs all wavelengths of EM radiation equally well, including the ones we can't see.

Question 8

Question
Which of the following statements is NOT true?
Answer
  • Geostationary satellites take 24 hours to orbit the Earth and therefore always remain above the same point on the ground.
  • Geostationary satellites are never in near-polar orbits -- they are always in equatorial orbits.
  • Earth observation satellites in a sun-synchronous orbit travel slightly East-to-West -- the opposite direction to the rotation of the Earth.
  • Some Earth observation satellites in LEO are near-equatorial, so that they only cover the tropical regions.
  • Sun synchronous orbits are always arranged to have a local solar time beneath the satellite at approximately 10:00-10:30 in the morning so as to minimise the cloud cover.

Question 9

Question
The albedo of Earth is the fraction of incident sunlight...
Answer
  • absorbed at Earth’s surface, and has a value of 49%
  • reflected at Earth’s surface, and has a value of 5%
  • absorbed by Earth’s surface and atmosphere, and has a value of 31%
  • reflected by Earth’s surface and atmosphere, and has a value of 31%
  • absorbed by Earth’s surface and atmosphere, and has a value of 69%

Question 10

Question
If a represents Earth’s albedo and P is the total power of sunlight incident on Earth, then the power radiated by Earth to space is approximately...
Answer
  • aP
  • (1-a)P
  • 1-aP
  • a(1-P)
  • a

Question 11

Question
An object will appear red to the naked eye if...
Answer
  • It scatters all visible wavelengths equally.
  • It scatters only red wavelengths and absorbs all the other visible wavelengths.
  • It absorbs only red wavelengths.
  • It transmits only red wavelengths.

Question 12

Question
An object will appear white to the naked eye if... (Note: more than one answer may be correct).
Answer
  • it scatterers all visible wavelengths equally.
  • it absorbs all visible wavelengths equally.
  • it scatters all wavelengths equally.
  • it transmits all wavelengths.
  • it absorbs all wavelengths equally.

Question 13

Question
Approximately what proportion of the mass of the Earth's atmosphere lies within the Troposphere?
Answer
  • 100%
  • 95%
  • 90%
  • 50%
  • 15%

Question 14

Question
Which of the following in NOT an advantages of satellite measurements?
Answer
  • Consistent measurements globally.
  • Rapid large area coverage.
  • Near continuous measurements over many years.
  • Making measurements above the atmosphere.
  • None of the other answers (they are all advantages)

Question 15

Question
Satellite observations always have to deal with [blank_start]trade-offs[blank_end]. One particular example is [blank_start]temporal[blank_end] coverage (frequency of measurements) versus level of [blank_start]detail[blank_end]. Typically, a single satellite that provides very [blank_start]frequent[blank_end] measurements will provide a [blank_start]low[blank_end] level of spatial detail.
Answer
  • trade-offs
  • temporal
  • general
  • detail
  • data
  • frequent
  • infrequent
  • low
  • high

Question 16

Question
In the context of atmospheric measurements, the abbreviation "ppmv" means...
Answer
  • Parts per million by volume
  • Parts per mass of volume
  • Precipitation per mass volume
  • Particles per mass by volume

Question 17

Question
Which of the following cannot (yet) be measured from satellite?
Answer
  • Below ground biomass.
  • Above ground biomass.
  • mm scale ground surface displacements.
  • Atmospheric motion (wind).
  • Sea surface temperature.
  • Wind direction over the oceans.

Question 18

Question
The sky appears blue because atmospheric molecules are [blank_start]Rayleigh[blank_end] scatterers in the [blank_start]visible[blank_end] part of the spectrum. Light at the [blank_start]blue[blank_end] end of the spectrum is therefore [blank_start]scattered[blank_end] significantly more than at the [blank_start]red[blank_end] end, where the light mostly passes through atmosphere.
Answer
  • Rayleigh
  • Mie
  • Optical
  • Blackbody
  • visible
  • infra-red
  • ultraviolet
  • microwave
  • blue
  • green
  • yellow
  • scattered
  • absorbed
  • transmitted
  • red

Question 19

Question
Which of the following exhibit signs of "optical scattering" in the visible part of the spectrum? (There may be more than one correct answer -- click all that apply).
Answer
  • Polar bear fur.
  • Milk.
  • White emulsion paint.
  • Clouds.
  • Healthy leaves.
  • The atmosphere.

Question 20

Question
Why are long term (decadal) measurements from satellites difficult, and how is this problem overcome?
Answer
  • Satellites don't last more than a few years. The solution is to have a period of overlap in sequential missions to perform an inter-calibration between the sensors.
  • Satellites don't last more than a few years. The solution is to make sure sequential missions have exactly the same sensor on board.
  • Satellites typically don't last more than a few years because of fuel constraints. The solution is to increase the lifetime to tens of years by carrying more fuel.
  • The measurement instruments degrade over time. The solution is to replace the instrument in situ (i.e. in orbit).

Question 21

Question
Which of the following might a "passive" remote sensing system measure? (Select all that apply).
Answer
  • Emitted radiation from the Earth's surface.
  • Emitted radiation from the atmosphere.
  • Solar NIR radiation scattered off the surface of the Earth.
  • Solar radiation scattered off the atmosphere.
  • Scattered microwave radiation originating from the remote sensing system.
  • Scattered NIR radiation originating from the remote sensing system (e.g. a laser).
  • Solar visible radiation scattered off the surface of the Earth.
  • Solar radiation after it has passed through the atmosphere.

Question 22

Question
The five different resolutions are: [blank_start]spatial[blank_end] (based on angular resolution of the instrument), [blank_start]range[blank_end] (based on pulse size for active instruments), [blank_start]spectral[blank_end] (ability to distinguish in wavelength), [blank_start]radiometric[blank_end] (ability to distinguish different brightness levels), [blank_start]temporal[blank_end] (ability to distinguish events in time).
Answer
  • spatial
  • range
  • spectral
  • radiometric
  • temporal

Question 23

Question
Which of the following best describes the general term "resolution"?
Answer
  • The ability to distinguish (separate) two infinitely narrow signals in some measurement system.
  • The size (on the ground) of a pixel in an image.
  • The area (on the ground) of a pixel in an image.
  • The ability to distinguish (separate) two point targets on the ground.

Question 24

Question
When a blackbody warms up, it will emit radiation with [blank_start]more[blank_end] total energy and with a [blank_start]peak[blank_end] that will go from [blank_start]longer[blank_end] wavelengths to [blank_start]shorter[blank_end] wavelengths.
Answer
  • more
  • less
  • equal
  • longer
  • shorter
  • peak
  • minimum
  • shape

Question 25

Question
The Earth's greenhouse effect is mostly driven by which gas?
Answer
  • Water vapour
  • Carbon dioxide
  • Methane
  • Nitrogen gas
  • Oxygen

Question 26

Question
1) What frequency of EM radiation corresponds to a wavelength of a) 600nm, and b) 3cm?
Answer
  • (a) 500 THz and (b) 10 GHz
  • (a) 50 THz and (b) 10 GHz
  • (a) 500 THz and (b) 1 GHz
  • (a) 500 GHz and (b) 10 GHz
  • (a) 500 THz and (b) 10 THz

Question 27

Question
Domestic electricity supply is at a frequency of 50Hz. What wavelength of electromagnetic radiation would you expect as a result of this oscillating electric field?
Answer
  • 6000km
  • 3000km
  • 600km
  • 60km
  • 6m

Question 28

Question
Use Wein’s Law for this question (find this on the NLN tutorials or a source of your choice). If you heat an iron bar in a furnace, at what temperature would the rod be at to have a peak in its radiance curve in the middle of the visible range (about 550nm)?
Answer
  • T= 5269 K
  • T= 527 K
  • T= 527 ˚C
  • T= 5269˚C

Question 29

Question
Use Wein’s Law for this question (find this on the NLN tutorials or a source of your choice). If you have an iron bar at the ambient room temperature (say about 20°C) what frequency and wavelength would the maximum be? In what region of the EM spectrum is this?
Answer
  • 10µm or 30 THz. Thermal IR.
  • 10µm or 10 THz. Thermal IR.
  • 30µm or 10 THz. Thermal IR.
  • 1µm or 100 THz. Near IR.
  • 1µm or 30 THz. Near IR.

Question 30

Question
If a satellite has an inclination angle of 98° it will pass the equator on the ascending pass with a bearing of [blank_start]352˚[blank_end]. At its closest pass to the poles, its bearing will be [blank_start]270˚[blank_end]? (Note, bearings are relative to North).
Answer
  • 352˚
  • 8˚
  • 90˚
  • 270˚
  • 188˚
  • 172˚

Question 31

Question
An EO satellite has an inclination angle of 98° and is orbiting at an altitude of 800km. The orbital period is [blank_start]101mins[blank_end]. If the swath width is 100km, the shortest time this satellite could conceivably provide global coverage is approximately [blank_start]28 days[blank_end]. The instrument measurements [blank_start]do not[blank_end] cover the polar regions.
Answer
  • 101mins
  • 90 mins
  • 3 hours
  • 120 mins
  • 28 days
  • 22 days
  • 28 hours
  • 280 days
  • do not
  • do
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