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Remote Sensing > remote sensing > Flashcards

remote sensing Flashcards

1
Q

Which of the following is not EMR?

(a) Near infrared.
(b) Radio wave.
(c) Thermal radiation.
(d) Ultrasound.

A

(d) Ultrasound

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2
Q

The energy of a photon is given as Q = hv or Q = hc/λ and therefore:

(a) the energy level of the EMR is irrelevant to its wavelength.
(b) the EMR with higher frequency has lower energy.
(c) the EMR with shorter wavelength has lower energy.
(d) blue light transmits more energy than red light

A

(d) blue light transmits more energy than red light

Because blue light has a shorter wavelength than red light. The longer the wavelength of EMR the lower its energy content. EMR with higher frequency has higher energy.

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3
Q

The Wien’s displacement law states: λm = A/T where A = 2898 µmK, the peak radiation wavelength of the Earth as a black body of 300 K is:

(a) 0.966 mm
(b) 9.66 µm
(c) 9.66 nm
(d) 0.966 µm

A

(b) 9.66 µm

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4
Q

Which one of the following statements is WRONG?

(a) Rayleigh scattering in atmosphere happens when the size of scattering particles is greater than the wavelength of EMR.
(b) Mie scattering happens when the particle diameter is equivalent to the wavelength of EMR.
(c) Vapour particles in clouds are non-selective scatters to visible light.
(d) Rayleigh scattering is more significant to blue light than to red light.

A

(a) Rayleigh scattering in atmosphere happens when the size of scattering particles is greater than the wavelength of EMR.

TRUE: Rayleigh scatter is common when radiation interacts with atmospheric molecules and other tiny particles that are much smaller in diameter than the wavelength of the interacting radiation

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5
Q

An atmospheric window is:

(a) a spectral range where there is no atmospheric scattering effects.
(b) a spectral range in which the atmosphere is transparent to EMR.
(c) a spectral range in which the energy of EMR is absorbed by the atmosphere.
(d) A clear sky area without clouds.

A

(b) a spectral range in which the atmosphere is transparent to EMR.

An atmospheric absorption zone is (c) a spectral range in which the energy of EMR is absorbed by the atmosphere.

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6
Q

Which of the following spectral range is in an atmospheric window and of the maximum solar radiation?

(a) Shortwave infrared.
(b) Microwave.
(c) Thermal infrared.
(d) Visible.

A

(d) Visible.

Atmospheric windows occur in the visible, infrared, and radio regions of the spectrum. Higher solar radiation occurs in spectural ranges of shorter wavelength and higher frequency.

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7
Q

The spectral reflectance of a material is:

(a) the reflectivity of the material to EMR at a particular wavelength.
(b) the reflectivity of the material to visible light.
(c) the reflectivity of the material to thermal radiation.
(d) the temperature of the material.

A

(a) the reflectivity of the material to EMR at a particular wavelength.

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8
Q

Which of the following statement about a geostationary orbit is NOT TRUE?

(a) A geostationary orbit enables a satellite to orbit at a speed and direction which matches the rotation of the Earth.
(b) A geostationary orbit is 36000km above the Earth equator.
(c) A geostationary orbit enables high spatial resolution Earth observation.
(d) A geostationary orbit enables Earth observation day and night.

A

(c) A geostationary orbit enables high spatial resolution Earth observation.

TRUE: Satellites in geostationary orbits can observe and collect information continuously over specific areas but at relatively low spatial resolution because of the large distance.

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9
Q

For an Earth observation satellite on circular, near-polar, sun synchronous orbits, which statement below is correct?

(a) It can image entire Earth’s surface except the regions near the North and South poles.
(b) It can take images of near infra-red spectral bands on both descending and ascending passes.
(c) It can take images only on descending passes.
(d) It images different areas of the Earth surface at very different local time

A

(a) It can image entire Earth’s surface except the regions near the North and South poles.

The ascending pass is on the night-time side and the descending pass is on the day-time side of the Earth. Solar illumination is available only during day-time so get day time images on decending path and thermal on decending path.

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10
Q

A push-broom scanner allows much longer dwell time than an across-track scanner and therefore the following resolutions can be improved except:

(a) spectral resolution.
(b) spatial resolution.
(c) temporal resolution.
(d) radiometric resolution.

A

(c) temporal resolution

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11
Q

A digital image is a:

(a) dataset of coordinates: x, y and z.
(b) two dimensional array of numbers.
(c) two dimensional array of symbols.
(d) matrix.

A

(b) two dimensional array of numbers.

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12
Q

Which of the following colour vectors is on the GREY LINE in a RGB colour cube?

(a) r=127, g=0, b=0
(b) r=100, g=0, b=255
(c) r=135, g=135, b=135
(d) r=130, g=230, b=200

A

(c) r=135, g=135, b=135

Because r=g=b

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13
Q

A point operation..

A

does not involve neighbouring pixels

And is irrelevant to pixel position

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14
Q

Which of the following should not, strictly speaking, be called ‘Earth observation’ remote sensing?

(a) Taking colour photographs of the land surface from an airborne camera.
(b) Acquiring multi-spectral images of the Earth’s surface from a satellite sensor.
(c) Measuring the Earth’s magnetic or gravity field from a ground or airborne sensor.
(d) Acquiring thermal images of cities during the night from an airborne sensor.

A

(c) Measuring the Earth’s magnetic or gravity field from a ground or airborne sensor.

Remote sensing is the technology of taking images from satellites, space crafts and air planes, and the application of these imagery data

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15
Q

What defines a Standard False Colour Composite image?

A

(a) NIR, Red and Green bands displayed as RGB.

NIR band displayed in red, Red band in green and Green band in blue. Highlights vegetation in red very effectively.

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16
Q

When choosing remotely sensed datasets for a project, which of the following would NOT be appropriate for mapping at a scale of ≤ 1:10,000? (detailed mapping)

(a) Ikonos or GeoEye.
(b) Quickbird or Worldview.
(c) SPOT 6 Pan.
(d) Aster or Landsat ETM+

A

(d) Aster or Landsat ETM+

These are used for regional mapping (1:50,000) along with: SPOT 1-4; ERS; Envisat; PALSAR & Sentiel-1

Detailed mapping: Ikonos; Quickbird; GeoEye; Worldview; SPOT 5, 6 &7; Pleiades; SkySat-1

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17
Q

With respect to the spectral reflectance of healthy, chlorophyll-bearing vegetation, which of the following statements is true?

(a) Reflectance is high in the Green, and low in the NIR.
(b) Reflectance is low in both NIR and SWIR.
(c) Reflectance is high in the Blue, Green and Red.
(d) Reflectance is very high in the NIR, and low in both the Blue and Red.

A

(d) Reflectance is very high in the NIR, and low in both the Blue and Red.

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18
Q

Broad-band multi-spectral images (e.g. Landsat) can be used very effectively for:

(a) Lithological identification.
(b) Species level mineral identification.
(c) Lithological discrimination.
(d) Species level mineral discrimination.

A

(c) Lithological discrimination.

Medium resolution (used for regional scale lithological discrimination and mapping) – Landsat, Aster – SPOT (1-4)

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19
Q

If an image target object appears bright in the visible bands and dark in the thermal band, which of the following statements is true?

(a) The object has low albedo and high emissivity.
(b) The object has low albedo and low emissivity.
(c) The object has high albedo and low emissivity.
(d) The object has high albedo and high emissivity.

A

(c) The object has high albedo and low emissivity

Reflectance and emissivity are opposites of one another. If an object has high albedo (strongly reflective) it cannot be absorbing at the same time, and therefore its emissivity will be low (reflect sunlight and remain cool; Dark in TIR image (e.g Landsat band 6). And vice versa. Dark in visible and bright in thermal = (a) The object has low albedo and high emissivity (Absorb sunlight and become warm; Bright in TIR image (e.g. Landsat band 6)

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20
Q

What colour should vegetation appear in a Landsat TM (or ETM+) standard false colour composite image of bands 432 in RGB?

A

(a) Red

21
Q

What colour should red soils appear in a Landsat TM (or ETM+) standard false colour composite image of bands 432 in RGB?

A

Greenish

22
Q

What colour should red soils appear in a Landsat TM (or ETM+) standard false colour composite image of bands 531 in RGB?

A

Olive-Greenish.

23
Q

What colour should vegetation appear in a Landsat TM (or ETM+) standard false colour composite image of bands 531 in RGB?

A

Dark reddish brown.

24
Q

Which of the following definitions is UNTRUE of GIS?

(a) A general purpose computer-based tool for storing, analysing, displaying and managing geospatial information.
(b) A tool for mapping and analysing things that exist on and events that happen on Earth.
(c) An expert mapping system.
(d) Technology that enables geographic analysis in 2D and pseudo-3D

A

(c) An expert mapping system.

GIS is not an expert system, but a system for experts! Most GIS cannot accommodate true 3D, only pseudo-3D (or 2.5D), nor dipping structures. Micromine is a true 3D GIS specifically for the extractive industries.

25
Q

Which of the following statements is UNTRUE?

(a) Raster data have fixed accuracy determined by spatial resolution.
(b) Raster data provides regularly sampled information.
(c) A single raster file can represent multiple attributes.
(d) Raster file size is affected by spatial resolution and is large compared to vector.

A

(c) A single raster file can represent multiple attributes.

TRUE: Each raster grid represents the variance of one attribute.

26
Q

Identify the core benefit of spatial information which allows GIS to answer the question of whether London Zoo shares a boundary with Regent’s Park?

(a) Proximity.
(b) Containment.
(c) Overlay.
(d) Adjacency.

A

(d) Adjacency.

Side note: ‘Overlay’ – algebra applied to layers/objects (e.g. layer1 + layer2);
Proximity – what is the distances between objects in one layer?

27
Q

Mathematical operations carried out between GIS layers are known as:

(a) Map cartography.
(b) Map algebra.
(c) Map topology.
(d) Map geometry.

A

(b) Map algebra.

28
Q

Identify the core benefit of spatial information which allows GIS to answer the question of whether the boating lake lies entirely within Regent’s Park?

(a) Proximity.
(b) Containment.
(c) Overlay.
(d) Adjacency.

A

(b) Containment.

Side note: ‘Overlay’ – algebra applied to layers/objects (e.g. layer1 + layer2);
Proximity – what is the distances between objects in one layer?

29
Q

Georeferencing – which statement is untrue?

(a) Georeferencing is vital for image interpretation.
(b) Georeferencing is essential for data integration and spatial analysis in GIS.
(c) Georeferencing can be either numerical or based on names.
(d) Georeferencing should be unique and persistent in time.

A

(a) Georeferencing is vital for image interpretation.

30
Q

Variables like slope, elevation and rainfall intensity are represented in a GIS most effectively using:

(a) Vector data.
(b) Metadata.
(c) Raster data.
(d) Tabular data.

A

(c) Raster data.

Raster surfaces are used to represent any continuously sampled phenomenon (i.e. any variable): elevation, rainfall, magnetic intensity etc

31
Q

Faults and boundaries are represented in a GIS most effectively using:

A

(a) Vector polyline data.

Vector data comprises of:
Points, vertices or nodes e.g. geochemical sample points, boreholes;
Polylines, lines or arcs e.g. geological boundaries, faults, topographic features;
Polygons or areas e.g. geological outcrops and exposures, contours

32
Q

Which of the following is not a valid and commonly used map projection type?

(a) Cyclic.
(b) Planar.
(c) Conic.
(d) Cylindrical.

A

(a) Cyclic.

Planar, cylindrical and conic are the basic projection types.

33
Q

Wien’s displacement law states: λm = A/T where A = 2898 µmK, the peak radiation wavelength of the Sun as a black body of 6000 K is:

(a) 0.483 mm
(b) 4.83 µm
(c) 48.3 nm
(d) 0.483 µm

A

(d) 0.483 µm

34
Q

Which one of the following statements is correct?

a) Rayleigh scattering in atmosphere happens when the size of scattering particles is greater than the wavelength of EMR.
b) Mie scattering in atmosphere happens when the particle diameter is smaller than the wavelength of EMR.
c) Mie scattering in atmosphere is more significant to blue light than to red light.
d) Rayleigh scattering in atmosphere is more significant to blue light than to red light.

A

d) Rayleigh scattering in atmosphere is more significant to blue light than to red light.

The effects of Rayleigh scatter mainly occur in short wavelengths. In the visible spectral region, the wavelength of blue light is the shortest and then the Rayleigh scattering is the strongest and thus we see the sky in blue

35
Q

What is Mie scattering?

A

When atmospheric particle diameters are similar to the wavelength of EMR passing through it

36
Q

The visible-near infrared (VNIR) part of the spectrum occupies which wavelength range?

A

0.4 - 1.1µm

37
Q

What does the Electromagnetic radiation spectrum look like?

A
38
Q

Where do atmospheric windows occur?

A

Visible, infrared and radio regions

39
Q

Which of the following statement is NOT TRUE?

(a) Any colour that we see on a computer screen is a composition of three primary colours: red, green and blue.
(b) We can use RGB additive colour composition to generate false colour display.
(c) Three primary colours: RGB, are used as a tool to display imagery information beyond human vision capability.
(d) We cannot use images of red, green and blue spectral bands to generate a false colour display via RGB additive colour composition.

A

(d) We cannot use images of red, green and blue spectral bands to generate a false colour display via RGB additive colour composition.

40
Q

Each raster grid represents what?

A

the variance of one attribute

41
Q

Identify the core benefit of spatial information which allows GIS to answer the question of what is the distance between The Church and Regent’s Park?

A

Proximity

42
Q

What remotely sensed datasets can be used for detailed mapping at a scale of ≤ 1:10,000?

A

Ikonos; Quickbird; GeoEye; Worldview; SPOT 5, 6 &7; Pleiades; SkySat-1

43
Q

What remotely sensed datasets can be used for regional scale mapping at a scale of ≤ 1:50,000?

A

Aster, Landsat ETM+, SPOT 1-4; ERS; Envisat; PALSAR & Sentiel-1

44
Q

What is the property of vector spatial data that allows us to determine spatial relationships between connected objects?

A

Topology

45
Q

For an earth observation satellite on circular, near-polar, Sun-synchronous orbits, which statement below is correct?

(a) It images the entire Earth’s surface except the regions near the North and South poles every day.
(b) It can take near-infrared images on both descending and ascending passes.
(c) It cannot take thermal infrared images on ascending passes.
(d) It images different areas of the Earth’s surface at about the same local time

A

(a) It images the entire Earth’s surface except the regions near the North and South poles every day.

46
Q

Which statement about image resolution below is wrong?

(a) Higher spatial resolution means more grey levels in an image.
(b) Lower spatial resolution means less spatial detail in an image.
(c) A panchromatic image has lower spectral resolution than a multi-spectral image.
(d) More frequent re-imaging of the same scene means a higher temporal resolution.

A

(a) Higher spatial resolution means more grey levels in an image

47
Q

When does a satellite in a sun-synchronous orbit record reflected solar energy, and when does it record emitted (thermal) radiation?

A

Reflected solar energy on descending pass in day, when solar illumination is available

Thermal on ascending (in night) and descending passes

48
Q

For an earth observation satellite on circular, near-polar, Sun-synchronous orbits, which statement below is correct?

(a) It images the entire Earth’s surface except the regions near the North and South poles every day.
(b) It can take near-infrared images on both descending and ascending passes.
(c) It cannot take thermal infrared images on ascending passes.
(d) It images different areas of the Earth’s surface at about the same local time.

A

(d) It images different areas of the Earth’s surface at about the same local time.

It cannot image the entire earth surface every day, in a single day it will leave gaps

it can cover and image each area of the earth at a constant local time of day called local sun time

Remote Sensing (1 decks)

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