chapter 3 sensors and platforms part 2

Question 1

There are several broad categories of basic sensor system types such as

Answer 1

passive vs. active, and imaging vs. nonimaging

Question 2

Passive vs. active refers to

Answer 2

the illumination source of the system

Question 3

imaging vs. nonimaging refers to

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the form of the data

Question 4

A variety of different sensors fit in these categories, which are

Answer 4

not mutually exclusive.

Question 5

Passive sensors measure

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light reflected or emitted naturally from surfaces and objects

Question 6

Passive sensors measure light reflected or emitted naturally from surfaces and objects. Such instruments

Answer 6

merely observe

Question 7

Passive sensors measure light reflected or emitted naturally from surfaces and objects. Such instruments merely observe, and depend primarily on

Answer 7

solar energy

Question 8

Passive sensors measure light reflected or emitted naturally from surfaces and objects. Such instruments merely observe, and depend primarily on solar energy as the

Answer 8

ultimate radiation source

Question 9

Passive sensors measure light reflected or emitted naturally from surfaces and objects. Such instruments merely observe, and depend primarily on solar energy as the ultimate radiation source illuminating

Answer 9

surfaces and object

Question 10

Active sensors (such as ……………)

Answer 10

radar and lidar systems

Question 11

Active sensors (such as radar and lidar systems) first

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emit energy (supplied by their own energy source) and then measure the return of that energy after it has interacted with a surface.

Question 12

Use of data collected by passive sensors often requires

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accurate measurements of solar radiation reaching the surface at the time the observations were made

Question 13

Active sensors :
Use of data collected by passive sensors often requires accurate measurements of solar radiation reaching the surface at the time the observations were made. This information allows for the

Answer 13

correction of “atmospheric effects”

Question 14

Use of data collected by passive sensors often requires accurate measurements of solar radiation reaching the surface at the time the observations were made. This information allows for the correction of “atmospheric effects” and results in

Answer 14

data or images that are more representative of actual surface characteristics.

Question 15

Remote sensing data are the recorded representation of

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radiation reflected or emitted from an area or object

Question 16

When measuring the reflected or emitted energy, ………………… can be used

Answer 16

either imaging or nonimaging sensors

Question 17

Data from imaging sensors can be processed to produce

Answer 17

an image of an area, within which smaller parts of the sensor’s whole view are resolved visually

Question 18

Nonimaging sensors usually are

Answer 18

hand held devices

Question 19

Nonimaging sensors usually are hand held devices that

Answer 19

register only a single response value, with no finer resolution than the whole area viewed by the sensor

Question 20

Nonimaging sensors usually are hand held devices that register only a single response value, with no finer resolution than the whole area viewed by the sensor, and therefore

Answer 20

no image can be made from the data

Question 21

Nonimaging sensors usually are hand held devices that register only a single response value, with no finer resolution than the whole area viewed by the sensor, and therefore no image can be made from the data. These single values can be referred to as

Answer 21

a type of “point” data

Question 22

These single values can be referred to as a type of “point” data, however some small area is typically involved depending on

Answer 22

the sensor’s spatial resolution

Question 23

Image and nonimage data each have particular uses. Nonimage data give information for

Answer 23

one specific (usually small) area or surface cover type

Question 24

Nonimage data give information for one specific (usually small) area or surface cover type, and can be used to

Answer 24

characterize the reflectance of various materials occurring in a larger scene and to learn more about the interactions of electromagnetic energy and objects.

Question 25

Image data provide an opportunity to look at

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spatial relationships, object shapes, and to estimate physical sizes

Question 26

Image data provide an opportunity to look at spatial relationships, object shapes, and to estimate physical sizes based on

Answer 26

the data’s spatial resolution and sampling

Question 27

Image data are desirable when ……………………….. (such as …………..) is needed

Answer 27

spatial information 
(mapped output)

Question 28

Image data provide an opportunity to look at spatial relationships, object shapes, and to estimate physical sizes based on the data’s spatial resolution and sampling. Image data are desirable when spatial information (such as mapped output) is needed. This text refers primarily to

Answer 28

imaging sensors and data.

Question 29

Images produced from remote sensing data can be either

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analog (such as a photograph) or digital (a multidimensional array or grid of numbers)

Question 30

Digital data can be analyzed by

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studying the values using calculations performed on a computer

Question 31

Digital data can be analyzed by studying the values using calculations performed on a computer, or processed to produce

Answer 31

an image for visual interpretation

Question 32

Image interpretation is used to

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decipher information in a scene

Question 33

In the past, image interpretation was done largely using

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subjective visual techniques

Question 34

In the past, image interpretation was done largely using subjective visual techniques, but with the development and ongoing advancement of

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computer technology, numeric or digital processing

Question 35

In the past, image interpretation was done largely using subjective visual techniques, but with the development and ongoing advancement of computer technology, numeric or digital processing has become

Answer 35

a powerful and common interpretation tool.

Question 36

In many cases, image interpretation involves the combination of both

Answer 36

visual and digital techniques

Question 37

In many cases, image interpretation involves the combination of both visual and digital techniques. These techniques

Answer 37

utilize a number of image features

Question 38

In many cases, image interpretation involves the combination of both visual and digital techniques. These techniques utilize a number of image features including

Answer 38

tone and color, texture, shape, size, patterns, and associations of objects

Question 39

The human eye and brain are generally thought to more easily process the ………………… of an image

Answer 39

spatial charactaristics

Question 40

The human eye and brain are generally thought to more easily process the spatial characteristics of an image, such as

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shape, patterns and how objects are associated with one another

Question 41

Computers usually are better suited for

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rapid analysis of the spectral elements of an image

Question 42

Computers usually are better suited for rapid analysis of the spectral elements of an image such as

Answer 42

tone and color

Question 43

Sophisticated computer software that can perform like the human eye and brain may be

Answer 43

more commonly available in the future.

Question 44

Passive sensors are the most common sensor type for

Answer 44

vegetation related remote sensing

Question 45

This is not only because passive sensor systems are generally

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simpler in design (built only to receive energy)

Question 46

Passive sensors are the most common sensor type for vegetation related remote sensing. This is not only because passive sensor systems are generally simpler in design (built only to receive energy) but also because

Answer 46

portions of the solar spectrum provide very useful information for monitoring plant and canopy properties.

Question 47

A major limitation of passive systems is that in most cases they require

Answer 47

sunlight in order for valid and useful data to be acquired.

Question 48

A major limitation of passive systems is that in most cases they require sunlight in order for valid and useful data to be acquired. Consequently,

Answer 48

deployment of or data acquisition by passive sensors is very dependent on lighting (time of day, time of year, latitude) and weather conditions,

Question 49

A major limitation of passive systems is that in most cases they require sunlight in order for valid and useful data to be acquired. Consequently, deployment of or data acquisition by passive sensors is very dependent on lighting (time of day, time of year, latitude) and weather conditions, since cloud cover can

Answer 49

interfere with the path of solar radiation from the sun to the surface and then to the sensor.

Question 50

The signals detected by passive sensors can be ……………….. due to ….

Answer 50

greatly altered due to atmospheric effects

Question 51

The signals detected by passive sensors can be greatly altered due to atmospheric effects, especially in the

Answer 51

shorter wavelengths of the solar spectrum

Question 52

The signals detected by passive sensors can be greatly altered due to atmospheric effects, especially in the shorter wavelengths of the solar spectrum that are

Answer 52

strongly scattered by the atmosphere

Question 53

The signals detected by passive sensors can be greatly altered due to atmospheric effects, especially in the shorter wavelengths of the solar spectrum that are strongly scattered by the atmosphere. These effects can be

Answer 53

minimized (but not eliminated)

Question 54

The signals detected by passive sensors can be greatly altered due to atmospheric effects, especially in the shorter wavelengths of the solar spectrum that are strongly scattered by the atmosphere. These effects can be minimized (but not eliminated) by

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collecting data only under very clear and dry atmospheric conditions

Question 55

Sophisticated atmospheric correction routines now exist to

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remove atmospheric effects from data acquired by passive sensors

Question 56

The most common sensor system is the

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photographic camera

Question 57

The most common sensor system is the photographic camera – a

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simple passive sensor

Question 58

Many of the historic developments in remote sensing were directly related to the development of

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photographic systems

Question 59

Camera systems are similar in design to

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the human eye

Question 60

Camera systems are similar in design to the human eye. Both have

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a lens at one end of an enclosed chamber and a light-sensitive material (film for a camera and the retina for an eye) at the other

Question 61

In both systems, an iris is used to

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control the amount of light that can strike the film/retina

Question 62

In a camera, a shutter is placed

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between the lens and film to control how long the light can strike the film

Question 63

Filters can be attached

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in front of a lens

Question 64

Filters can be attached in front of a lens to

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restrict the wavelength of light permitted to strike the film

Question 65

A radiometer is

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an instrument designed to measure the intensity of electromagnetic radiation in a set of wavebands ranging from the ultraviolet to microwave wavelengths.

Question 66

A radiometer is an instrument designed to measure the intensity of electromagnetic radiation in a set of wavebands ranging from the ultraviolet to microwave wavelengths. The radiometers discussed here are called

Answer 66

electro-optic sensors

Question 67

The radiometers discussed here are called electro-optic sensors because they

Answer 67

measure electromagnetic energy using optical techniques and electronic detectors

Question 68

The radiometers discussed here are called electro-optic sensors because they measure electromagnetic energy using optical techniques and electronic detectors. Though they are only capable of

Answer 68

recording a single data value for their view area, if they are mounted in a scanner device images can be produced.

Question 69

Radiometers are similar in design to a

Answer 69

camera

Question 70

Radiometers are similar in design to a camera in that they have

Answer 70

an opening for the light to enter, lenses and mirrors for the light to pass through

Question 71

Radiometers are similar in design to a camera in that they have an opening for the light to enter, lenses and mirrors for the light to pass through, but instead of film, they have

Answer 71

an electronic detector

Question 72

Radiometers are similar in design to a camera in that they have an opening for the light to enter, lenses and mirrors for the light to pass through, but instead of film, they have an electronic detector to

Answer 72

record the intensity of electromagnetic energy

Question 73

As energy hits the detector, a signal proportional to the incoming irradiance is processed to either a

Answer 73

digital or analog output that can be recorded.

Question 74

Detectors for radiometers have been devised to measure

Answer 74

wavelengths from 0.4 to 14 micrometers.

Question 75

Detectors for radiometers have been devised to measure wavelengths from 0.4 to 14 micrometers. Although some radiometers can detect this entire range of wavelengths, most only measure

Answer 75

selected wavebands in this range

Question 76

Radiometers that measure more than one waveband are called

Answer 76

multispectral radiometers

Question 77

Radiometers that measure more than one waveband are called multispectral radiometers. For this type of radiometer, the light

Answer 77

must be separated into discrete wavebands

Question 78

Radiometers that measure more than one waveband are called multispectral radiometers. For this type of radiometer, the light must be separated into discrete wavebands so that

Answer 78

multiple waveband or multichannel readings can be taken

Question 79

For this type of radiometer, the light must be separated into discrete wavebands so that multiple waveband or multichannel readings can be taken. This separation can be done using

Answer 79

filters, prisms or other sophisticated techniques

Question 80

Non-imaging radiometers are commonly used as

Answer 80

research tools to better understand how light interacts with objects

Question 81

Non-imaging radiometers are commonly used as research tools to better understand how light interacts with objects, for

Answer 81

spectral characterization of a variety of surfaces, and for atmospheric measurements.

Question 82

Non-imaging radiometers are commonly used as research tools to better understand how light interacts with objects, for spectral characterization of a variety of surfaces, and for atmospheric measurements. Another common use is to

Answer 82

measure the quantity and quality of solar energy

Question 83

Another common use is to measure the quantity and quality of solar energy. These measurements can in turn be used to

Answer 83

correct other imaging and nonimaging measurements for atmospheric effects.