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Atmospheric remote sensing > chapter 4 > Flashcards

chapter 4 Flashcards

1
Q

aerial photograph

A

any photograph taken from the air

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2
Q

An aerial photograph, in broad terms, is any photograph taken from the air. Normally, air photos are taken …………………… using a ……………………………………..

A

vertically from an aircraft

highly-accurate camera.

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3
Q

There are several things you can look for to determine what makes one photograph different from another of the same area including

A

type of film, scale, and overlap

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4
Q

Other important concepts used in aerial photography are

A

stereoscopic coverage, fiducial marks, focal length, roll and frame numbers, and flight lines and index maps.

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5
Q

Optics refer to

A

lenses and the geometry of light retrieval in a camera

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6
Q

Optics refer to lenses and the geometry of light retrieval in a camera. The lenses in a camera are responsible for

A

focusing and zooming on an object

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7
Q

Before light reflected from an object ………………………, it must pass through

A

strikes the film

one or more lenses

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8
Q

As light passes through a lens, it is

A

bent to focus the imaged object on the film

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9
Q

To minimize distortions associated with the use of ………………

A

single lenses

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10
Q

To minimize distortions associated with the use of single lenses, most camera lenses are actually composed of …………………………. that work in concert to

A

multiple lenses

form an image onto the film

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11
Q

most air photo missions are …………. using ………………

A

flown

black and white film

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12
Q

most air photo missions are flown using black and white film, however ……………………………………………..are sometimes used for special projects

A

colour, infrared, and false-colour infrared film

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13
Q

Film in a camera is used to record the image that passes through the

A

lens

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14
Q

Photographic film is composed of

A

a durable base

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15
Q

Film in a camera is used to record the image that passes through the lens. Photographic film is composed of a durable base, which is coated with a ………………………….. known as the …………………..

A

light-sensitive layer know as the emulsion

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16
Q

During the short time that a shutter is open

A

light strikes the film and leaves a latent image on the emulsion

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17
Q

. During the short time that a shutter is open, light strikes the film and leaves a latent image on the emulsion. This image can be made visible by

A

the process of developing and printing.

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18
Q

Emulsions are made of

A

materials sensitive to particular regions of the electromagnetic spectrum

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19
Q

Emulsions are made of materials sensitive to particular regions of the electromagnetic spectrum. For example,

A

some film is only sensitive to visible light, whereas other film is sensitive to near-infrared light

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20
Q

In color film, the emulsion is composed of

A

three layers, with each being sensitive to different wavelengths of light,

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21
Q

In color film, the emulsion is composed of three layers, with each being sensitive to different wavelengths of light, normally

A

blue, green and red light.

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22
Q

With black and white film, the emulsion is sensitive to

A

to a broad spectrum of light

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23
Q

Film emulsions are generally limited to recording wavelengths between

A

0.4 to 0.9 micrometers

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24
Q

Black and white film sensitive to

A

visible light

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25
Q

black and white film sensitive to

A

infrared wavelengths

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26
Q

Black and white film sensitive to visible light and black and white film sensitive to infrared wavelengths can also be used for

A

remote sensing purposes

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27
Q

Film speed is another quality of

A

emulsions that is important for aerial photography

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28
Q

Film speed refers to

A

the quantity of light that is needed to expose the emulsion

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29
Q

Fast film requires

A

less light than slow film to record the same image

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30
Q

If the camera platform is moving, one would want to use ………………………. to …………………………………………….

A

a high speed film to reduce the blurring effects of the moving camera

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31
Q

If the camera platform is moving, one would want to use a high speed film to reduce the blurring effects of the moving camera. Unfortunately, there is a tradeoff between

A

film speed and image quality

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32
Q

the faster the film speed, the

A

grainier the image

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33
Q

, there is a tradeoff between film speed and image quality – the faster the film speed, the grainier the image. Because of this tradeoff, it is necessary to

A

carefully choose a film speed that will meet the requirements of the end user

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34
Q

Some sophisticated camera mounts have an

A

image motion compensator

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35
Q

Some sophisticated camera mounts have an image motion compensator that

A

reduces the blurring effect of the moving platform

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36
Q

Some sophisticated camera mounts have an image motion compensator that reduces the blurring effect of the moving platform, which potentially

A

allows the use of slower film

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37
Q

Focal length

A

the distance from the middle of the camera lens to the focal plane (i.e. the film)

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38
Q

As focal length increases,

A

image distortion decreases

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39
Q

The focal length is precisely measured when

A

the camera is calibrated

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40
Q

The amount of image detail that can be recorded on film is directly related to

A

the distance between the lens and the film

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41
Q

The amount of image detail that can be recorded on film is directly related to the distance between the lens and the film (referred to as …………………)

A

focal length

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42
Q

As the focal length increases, the …………………………………………………. increases

A

detail that can be seen on the film

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43
Q

Increasing the focal length is commonly called

A

zooming in on an object.

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44
Q

Scale:

A

the ratio of the distance between two points on a photo to the actual distance between the same two points on the ground

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45
Q

Scale: the ratio of the distance between two points on a photo to the actual distance between the same two points on the ground (i.e. …………………………….)

A

1 unit on the photo equals “x” units on the ground

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46
Q

If a 1 km stretch of highway covers 4 cm on an air photo, the scale is calculated as follows:

A
47
Q

Another method used to determine the scale of a photo is to find the

A

ratio between the camera’s focal length and the plane’s altitude above the ground being photographed

48
Q

A

A

camera

49
Q

B

A

focal length

50
Q

C

A

film (focal plane)

51
Q

D

A

lens

52
Q

E

A

altitude above ground level (AGL)

53
Q

F

A

Altitude above sea level (ASL)

54
Q

If a camera’s focal length is 152 mm, and the plane’s altitude Above Ground Level (AGL) is 7600 m, using the same equation as above, the scale would be:

A
55
Q

Scale may be expressed three ways:

A
  • Unit Equivalent
  • Representative Fraction
  • Ratio
56
Q

A photographic scale of 1 millimetre on the photograph represents 25 metres on the ground would be expressed as follows:

A
  • Unit Equivalent - 1 mm = 25 m
  • Representative Fraction - 1/25 000
  • Ratio - 1:25 000
57
Q

Large Scale

A

Larger-scale photos (e.g. 1:25 000) cover small areas in greater detail

58
Q

A large scale photo simply means that ground features are at

A

a larger, more detailed size

59
Q

The area of ground coverage that is seen on the photo is …………………..smaller scales

A

less than at

60
Q

Small Scale

A

Smaller-scale photos (e.g. 1:50 000) cover large areas in less detail

61
Q

A small scale photo simply means that ground features are at

A

at a smaller, less detailed size

62
Q

The area of ground coverage that is seen on the photo is …………………………………. larger scales

A

greater than at

63
Q

In many remote sensing applications, it is important to restrict

A

the light entering the camera by the use of filters

64
Q

Color filters work by

A

absorbing a range of wavelengths while allowing other wavelengths to pass through

65
Q

Another filter type, known as neutral color filters,

A

do not alter the spectral composition of light, but instead reduce the amount of light of all wavelengths that pass through.

66
Q

Perhaps the most common color filter is an

A

antihaze filter

67
Q

Perhaps the most common color filter is an antihaze filter. These are ……………………………. filters

A

clear or yellow

68
Q

antihaze filter. These are clear or yellow filters, which

A

absorb out the shorter ultraviolet and blue wavelengths

69
Q

antihaze filter. These are clear or yellow filters, which absorb out the shorter ultraviolet and blue wavelengths that are substantially

A

scattered by particulates in the atmosphere.

70
Q

Another filter used for monitoring vegetation is

A

an infrared filter

71
Q

Another filter used for monitoring vegetation is an infrared filter, which

A

absorbs visible light and only allows infrared light to pass through

72
Q

Fiducial marks

A

small registration marks exposed on the edges of a photograph

73
Q

The distances between fiducial marks are

A

precisely measured when a camera is calibrated

74
Q

The distances between fiducial marks are precisely measured when a camera is calibrated, and this information is used by

A

cartographers when compiling a topographic map.

75
Q

A

A

fiducial marks

76
Q

B

A

Optical axis

77
Q

C

A

Principal point

78
Q

D

A

Lens

79
Q

Overlap

A

is the amount by which one photograph includes the area covered by another photograph, and is expressed as a percentage.

80
Q

The photo survey is designed to acquire ……………………………………… and ………………………………….

A

60% forward overlap (between photos along the same flight line) and 30% lateral overlap (between photos on adjacent flight lines).

81
Q

A

A

60 % overlap between photos (forward overlap)

82
Q

B

A

20 - 40 % overlap between flight lines (lateral overlap)

83
Q

Stereoscopic Coverage

A

the three-dimensional view which results when two overlapping photos (called a stereo pair)

84
Q

Stereoscopic Coverage: the three-dimensional view which results when two overlapping photos (called a stereo pair), are viewed using a

A

stereoscope.

85
Q

. Each photograph of the stereo pair provides a

A

slightly different view of the same area

86
Q

Each photograph of the stereo pair provides a slightly different view of the same area, which

A

the brain combines and interprets as a 3-D view.

87
Q

Roll and Photo Numbers

A

each aerial photo is assigned a unique index number according to the photo’s roll and frame

88
Q

For example, photo A23822-35 is the

A

35th annotated photo on roll A23822

89
Q

For example, photo A23822-35 is the 35th annotated photo on roll A23822. This identifying number allows you to

A

to find the photo in NAPL’s archive, along with metadata information such as the date it was taken, the plane’s altitude (above sea level), the focal length of the camera, and the weather conditions.

90
Q

Flight Lines and Index Maps

A

at the end of a photo mission, the aerial survey contractor plots the location of the first, last, and every fifth photo centre, along with its roll and frame number, on a National Topographic System (NTS) map

91
Q

Photo centres are represented by

A

small circles

92
Q

straight lines are drawn connecting the circles to show

A

photos on the same flight line.

93
Q

Photo centres are represented by small circles, and straight lines are drawn connecting the circles to show photos on the same flight line.

This graphical representation is called

A

air photo index map

94
Q

This graphical representation is called an air photo index map, and it allows you to relate

A

the photos to their geographical location

95
Q

Small-scale photographs are indexed on …………………… scale NTS map sheets

A

1:250 000

96
Q

larger-scale photographs are indexed on ………………………… scale NTS maps.

A

1:50 000

97
Q

A

A

flight line roll number

98
Q

B

A

photo number photo centre

99
Q

Aerial photography is one of the …………….forms of remote sensing

A

oldest

100
Q

Aerial photography is one of the oldest forms of remote sensing and it is

A

still used extensively today

101
Q

Aerial photography is one of the oldest forms of remote sensing and it is still used extensively today. It is usually the choice if

A

great spatial detail is needed

102
Q

Aerial photography records the

A

ever-changing cultural and natural features on the Earth’s surface.

103
Q

It shows geographical features such as:

A
  • mountains
  • canyons
  • flatlands
  • rivers from the source to the mouth
104
Q

It reveals the earth’s resources, such as:

A
  • lakes
  • forests
105
Q

It captures:

A
  • residential and industrial areas
  • road and rail networks
106
Q

It has many practical applications such as:

A
  • map-making
  • urban and rural planning
  • environmental impact studies
  • civil law cases
  • real estate evaluations
  • and even wall art
107
Q

vertical aerial photograph

A

A vertical photograph is one which has been taken with optical axis of camera approximately perpendicular to the horizontal plane

108
Q

A vertical photograph is one which has been taken with optical axis of camera approximately perpendicular to the horizontal plane. A deviation up to …………is acceptable

A

4°

109
Q

A deviation up to 4° is acceptable. This gives the map of the earth detail somehow in same

A

scale

110
Q
A

optical axis of camera

111
Q

Oblique Aerial Photographs

A

An oblique photograph is one which has been taken with the optical axis of the camera intentionally tilted from perpendicular position obliquely.

112
Q

The degree of tilt from the perpendicular further classifies oblique photographs into

A

high oblique photograph and low oblique photograph.

113
Q

A high oblique photograph is one which is taken with

A

the optical axis of the camera making an angle >30° with the vertical axis and which shows the apparent horizon on the photograph.

114
Q
A

optical axis of camera

Atmospheric remote sensing (9 decks)

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