Exam 2014, questions and answers PDF

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EVB221/UDB282 Remote Sensing of the Environment MCQ Test 2014 – November 8th Perusal Time: 10 minutes Working Time: 90 minutes

Student Name:

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INSTRUCTIONS:

1. Enter your name and student number on the appropriate line at the head of this page. 2. Enter your Surname, Initials, Subject Code, and Student Number in the appropriate positions on the ‘Test Answer Sheet’ 3. Attempt all 100 questions 4. All correct responses are of equal value 5. Indicate your response in accord with the ‘Marking Instructions’ shown on the ‘Test Answer Sheet’. 6. Hand in the attached question booklet and the ‘Test Answer Sheet’ before you leave the examination room

1) Which three of the following are descriptors of some of the seven elements of a remote sensing system? a) b) c) d)

Energy Source or Illumination and Radiation and the Atmosphere Interaction with the Target and Recording of Energy by the Sensor Land class/coverage classification Transmission, Reception, and Processing and Interpretation and Analysis

2) One of the five human senses only may be considered forms of "remote sensing". a) True b) False 3) Which of the following is NOT an example of non-intrusive remote sensing methods? a) ultrasounds, satellite weather maps, b) pressure, temperature and resistivity sensors for examining fluid integrity within a borehole c) speed radar, graduation photos, and sonar d) CAT scans, magnetic resonance imaging, and x-rays for examining our bodies 4) Which of the following statements is CORRECT with respect to electromagnetic radiation waves? a) b) c) d)

the Earth ‘vibrates’ at a very low frequency the Earth ‘vibrates’ at a very high frequency high-pitched sounds have long wavelengths and low frequencies low-pitched sounds have short wavelengths and high frequencies

5) Which of the following statements is INCORRECT when describing the Doppler Shift? a) sound and light waves are perceived to be compressed or expanded if the object producing them is moving relative to the sensor b) the same principle when applied to light is used by astronomers to see how quickly stars are moving towards us. c) as a rapidly moving sound source towards us, our ears tend to hear progressively lower sounds or frequencies until it reaches us d) then even lower frequencies as it moves further away 6) Which of the following statements is INCORRECT when describing attributes of colour? a) b) c) d)

Hue and saturation are inter-independent characteristics of colour. Hue refers to the wavelength of light, which we commonly call "colour" Saturation indicates how pure the colour is - how much white is mixed in with it Saturation indicates intensity of a colour - the degree to which it differs from white.

7) Which three of the following statements are CORRECT when describing the passing of sunlight through water droplets? a) individual colours in the sunlight are made visible resulting in the creation of a rainbow b) shorter wavelengths (violet, blue) are located in the inner part of the arc c) longer wavelengths (orange, red) are located along the outer arc. d) the constituent wavelengths are bent in varying amounts according to frequent 8) Scattering causes the atmosphere to have its own brightness which helps to illuminate the objects in the shadows. a) True b) False 9) If scattering of radiation in the atmosphere did not take place, then shadows would appear as jet black instead of being various degrees of darkness a) True b) False 10) Which two of the following descriptors are INCORRECT statements with respect to the colours we perceive? a) b) c) d)

colour will appear white if all visible wavelengths are absorbed by an object colour will appear black if all visible wavelengths are reflected from an object colour is combination of radiation interactions (absorption, transmission, reflection) colour represents the wavelengths being reflected

11) A camera cannot be described as being an example of both a passive and an active sensor. a) True b) False 12) Which two of the following are ACCURATE descriptions of attributes of the use of radar to measure the speed of travelling vehicles? a) the time delays cannot be calculated very accurately as the speed of the radiation is moving only slightly faster than most vehicles b) pulses of radiation are emitted, and the reflection of that radiation from the vehicle is detected and timed c) the time delays can be calculated very accurately as the speed of the radiation is moving only slightly faster than the acceleration d) the speed of the vehicle is determined by calculating time delays between the repeated emissions and reception of the pulses

13) Which two of the following statements are true comparisons of the attributes of photographic film and digital sensors? a) photographic film and digital sensors can record up to many thousands of levels of brightness b) photographic film has the clear advantage of recording extremely fine spatial resolution c) digital sensors have the advantage with spectral and radiometric resolution by being able to use extremely fine spectral bands d) digital imagery is much cheaper to capture 14) Sound cannot be considered to be a form of remote sensing. a) True b) False 15) When considering our eyes to be remote sensors, which of the following statements is INCORRECT? a) b) c) d)

our eyes detect radiation from the sun our eyes detect energy in the form of visible light from the sun allowing us to see light energy occupies a wide portion of the electromagnetic spectrum other types of light energy are invisible to our eyes

16) Given the speed of light is 3 x 108 metres/sec, the wavelength of radiation (in micrometres, 10-7) of a frequency of 500,000 x 109 Hz calculates as: a) b) c) d)

16 x 10-5 metres 6 x 10-7 metres 1.6 x 10-5 metres 0.6 x 10-7 metres

17) When discussing taking ‘photographs’ of both parts of the infrared portion of the electromagnetic spectrum (IR and NIR), which two of the following statements are CORRECT: a) photographic films cannot directly record emissive infrared b) photographic films can directly record emissive infrared but require extensive postprocessing c) photographic films in black and white and colour emulsions can directly record the reflective portion of the infrared band d) electronic devices are better technology to detect and record thermal infrared images

18) Which of the following statements is an INCORRECT explanation of why most remote sensing systems avoid detecting and recording wavelengths in the ultraviolet and blue portions of the spectrum? a) detecting and recording the ultraviolet and blue wavelengths of radiation is difficult because of scattering and absorption in the atmosphere. b) ozone gas in the upper atmosphere absorbs most of the ultraviolet radiation of wavelengths shorter than about 0.25 mm. c) after scattering the greater portion of the ultraviolet and blue wavelengths energy reaches and interacts with the Earth's surface d) Rayleigh scattering affects the shorter wavelengths more severely than longer wavelengths causing the remaining UV radiation and the shorter visible wavelengths to be scattered much more than longer wavelengths 19) Which three of the following statements are reasons why the best atmospheric conditions for remote sensing in the visible portion of the spectrum are around noon on a sunny, dry day with no clouds and no pollution.? a) dry, pollutant-free conditions would maximise the scattering and absorption that would take place due to water droplets and other particles in the atmosphere. b) cloud-free conditions would ensure that there will be uniform illumination c) cloud-free conditions ensure there will be no shadows from clouds. d) at noon the sun would be at its most directly overhead point thus reducing the distance radiation has to travel and therefore the effects of scattering to a minimum. 20) Which statement describes the light path for the phenomenon of seeing, on a clear night with the crescent or half moon showing, the outline and perhaps very slight detail of the dark portion of the moon? a) the light originates from the sun, refracted around to the dark side of the moon and then comes back to the earth and into your eye. b) the light originates from the sun, hits the earth, bounces off the bright side of the moon and then comes back to the earth and into your eye. c) the light originates from the sun, hits the earth, bounces up to the dark side of the moon and then comes back to the earth and into your eye. d) the light originates from the sun, hits the earth, reflected up and around to the dark side of the moon and then comes back to the earth and into your eye. 21) Which two of the following statements are CORRECT when describing a passive microwave radiometer? a) b) c) d)

it carries an illumination source it is a passive equivalent to the radar sensor it does not carry an illumination source it relies on detecting naturally emitted microwave energy

22) The reflectance curve diagram below illustrates the spectral response patterns of coniferous and deciduous trees. Which of the following statements is not applicable when attempting to use remote sending data to map the extent of the two tree species?

a) both types of trees will appear as similar shades of green to the naked eye, imagery or photography in the visible portion of the spectrum b) the tree type would be difficult to distinguish using any of the visible wavelengths c) in the near-infrared both types of trees are not clearly separable d) in the near-infrared both types of trees are clearly separable

23) Which three of the following are an advantage of displaying various wavelength ranges, or channels, in combination as colour images as opposed to examining each of the images individually? a) b) c) d)

combinations manifest themselves as subtle variations in colour variations in gray tone highlight subtleties in features helps identify combinations of reflectance between the different channels highlights features that we would not otherwise be able to see

24) Which two of the following explain why most of the images you see on television weather forecasts are from geostationary satellites? a) images provide broad coverage of the weather and cloud patterns on continental scales. b) images provide broad coverage of the rainfall and snowfall patterns on continental scales. c) meteorologists use these images to help determine in which direction the weather patterns are likely to go. d) limited repeat coverage capability of satellites with geostationary orbits allows these patterns to be monitored only intermittently. 25) The acronym IFOV stands for: a) b) c) d)

Instantaneous Field Off Vertical Instantaneous Field Of View Incremental Field of Vision Inferential Field Off Vertical

26) If the IFOV for all pixels of a scanner stays constant, which of the following statements is CORRECT? a) the ground area represented by pixels at the nadir will be at a smaller scale then those pixels which are off nadir b) the spectral resolution will vary from the image centre to the swath edge c) the spatial resolution will vary from the image centre to the swath edge d) the ground area represented by pixels off nadir will be at a larger scale then those pixels which are at nadir 27) Which two of the following are CORRECT statements with respect to sensor design? a) for high spatial resolution, the sensor has to have a small IFOV b) a small IFOV increases the amount of energy that can be detected within the IFOV c) narrowing the wavelength range detected for a particular channel or band increases the amount of energy detected without reducing spatial resolution but this reduces the spectral resolution of the sensor d) coarser spatial resolution reduces radiometric and/or spectral resolution 28) Which three of the following statements are correct when describing LFCs as were used by astronauts onboard the Space Shuttles? a) LFC photos need to be taken when the Earth's surface is being illuminated by the sun b) LFC is an acronym for Long Focal-length Camera c) LFCs have long focal lengths (305 mm) d) LFCs take high quality photographs covering several hundreds of kilometres in both dimensions 29) Which of the following statements is INCORRECT when describing FLIR systems? a) b) c) d)

FLIR is an acronym for Forward-Looking Infrared FLIR systems produce images very similar in appearance to nadir aerial photographs FLIR systems scan across the scene FLIR systems provide an oblique rather than nadir perspective of the Earth´s surface

30) The ERTS (Earth Resources Technology Satellite) program was renamed to Landsat just prior to the launch of the second satellite in the series. a) True b) False 31) Which of the following statements is INCORRECT when describing the Seasat satellite program? a) b) c) d)

first satellite launched in 1978 was the original name for the Landsat program was operational for 99 days only collected some of the first RADAR images from space

32) Which two of the following are correct statements with respect to the history of the numbering of MSS bands? a) the MSS sensor numbering scheme (bands 4, 5, 6, and 7) came from their numerical sequence after the three bands of the RBV sensors b) the MSS bands were renumbered from 1 to 4 when the RBV sensor was dropped from the satellite sensor payload of Landsat-5. c) the MSS sensor TM7 channel was added as an afterthought late in the original system design process d) the TM sensor TM6 and TM7 channels are out of order in terms of increasing wavelength. 33) What three advantages do satellite sensors have over aircraft sensors? a) satellite sensors "see" a much larger area of the Earth's surface than would be possible from a sensor onboard an aircraft b) satellite sensors are easy to reposition in order to respond to and monitor changes over time c) geometry of orbiting spacecraft with respect to the Earth relatively easy to calculate quite accurately facilitating correction of remote sensing images d) satellite sensors are continually orbiting the Earth 34) What three advantages do aircraft sensors have over satellites sensors? a) aircraft sensors can collect data at any time and over any portion of the Earth's surface b) aircraft sensor payload download does not rely on a sophisticated airborne digital transmission and transfer procedure c) aircraft sensors are restricted to collecting data over only those areas and during specific times dictated by their particular orbits d) easier to fix a sensor on an aircraft if a problem or malfunction develops 35) Which two of the following are an advantage or a disadvantage of the listed crossing time (local sun time) for a satellite in a near-polar sun-synchronous orbit carrying a sensor in the visible portion of the spectrum? a) an early morning crossing time would have the sun at a very low angle in the sky and would be good for emphasizing topographic effects b) an early morning crossing time would result in a reduction in shadows in areas of high relief c) a crossing time around noon would have the sun at its highest point in the sky and would provide the maximum and most uniform illumination conditions being useful for surfaces of low reflectance causing saturation of the sensor over high reflectance surfaces d) in mid afternoon, the illumination conditions would be more moderate with a phenomenon termed solar heating assisting recording reflected energy which is near minimum at this time of day.

36) Which of the following explain why a satellite sensor with large area coverage and fairly coarse spatial resolution would be best for monitoring the general health of vegetation coverage? a) large expanses of area are best covered by a sensor with a wide swath and broad coverage. b) spatial resolution of the sensor would be fairly coarse but fine detail are necessary for monitoring a broad class such as vegetation cover c) with broad areal coverage the revisit period would be shorter, increasing the opportunity for repeat coverage necessary for monitoring change d) high spectral resolution would be at a minimum requiring channels only in the visible and near-infrared regions of the spectrum 37) What are two of the advantages of Hyperspectral scanners which detect and record radiation in several (perhaps hundreds) of very narrow spectral bands a) allows for fine differentiation between targets based on detailed reflectance and absorption responses which are not detectable using the broad wavelength ranges of conventional multispectral scanners. b) increased sensitivity increases the volume of data collected making both storage and manipulation of the data much easier. c) analysing multiple images at one time or combining them becomes much easier d) measuring radiation over several small wavelength ranges allows building a continuous spectrum of the radiation detected for each pixel in an image 38) If the spectral range of the 288 channels of an airborne multispectral scanner is exactly 0.40 μm to 0.90 μm and each band covers a wavelength of 1.8 nm (nanometres, 10-9 m), can there be overlap between the bands? a) Yes b) No 39) What is the maximum value of the digital number which could be represented for an image with a radiometric resolution of 6 bits? a) b) c) d)

256 255 63 64

40) Which two of the following reasons explains why the use of a satellite-based scanning system is preferred to an aircraft-based system? a) a satellite scanner would provide adequate geometric accuracy in most mountainous regions b) given the same lighting conditions, shadowing would be a greater problem using aircraft imagery because of the deeper viewing angles c) geometric distortions as a result of large variations in relief would be amplified at aircraft altitudes much more than from satellite altitudes d) the broader viewing angle of aircraft imagery would eliminate the possibility for practical mapping in such areas.

41) Which of the following statements explains why data from the Landsat TM sensor would be considered less useful than data from the original MSS sensor? a) TM areal coverage of a scene is larger than that from a MSS scene b) TM offers higher spatial, spectral, and radiometric resolution c) TM has more spectral channels which are narrower and better placed in the spectrum for certain applications, particularly vegetation discrimination d) TM increases from 6 bits to 8 bits the recording of the radiometric resolution of the data. 42) 'K' band magnetrons are typically used for microwave oven power sources. a) True b) False 43) Which of the following is INCORRECT when describing the geometry of sidelooking radar (SLR)? a) SLR geometry can result in several image effects such as foreshortening, layover, and shadow b) SLR geometry makes radar quite useful for terrain analysis c) SLR geometry effects actually enhance the visual appearance of relief and terrain structure d) SLR geometry makes radar imagery an excellent choice for applications such as forestry and land-use mapping. 44) Which two of the following statements are true when explaining why a radar imaging device on the Space Shuttle was able to penetrate several metres below desert regions? a) b) c) d)

L-band radar - 23.5 cm wavelength - was used low frequency wavelength was used K-band radar – 1.5 cm wavelength – was used high frequency wavelength was used

45) Which of the following statements does NOT explain why, using interferometry, it is possible to measure the velocity of targets moving towards or away from a radar sensor? a) the returns are recorded from two antennas mounted on the platform b) the antennas are separated by a short distance in the along-track or flight direction c) the phase differences between the returns at each antenna are used to derive the speed of motion of targets in the illuminated scene d) two passes are required over the target 46) What two of the following conditions must be in place to create a transmitted wave with ...