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Remote Sensing > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Photograph Vs Image?

A

Photograph: film or analog
Image: Digital

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2
Q

Air photos vs Maps

A

Air
- pictorial detail
- current
- sequence
- distortions
Maps
- better topographic representation
- annotations
- distortions

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3
Q

Black and white infrared

A
  • only covers one spectral signature (one band)
  • Only detects IR energy (infrared)
  • higher contract between land and water
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4
Q

Black & White Panchromatic

A
  • spectral signature is much larger (covers larger electromagnetic spectrum)
  • contrast is less between water & land
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5
Q

Natural Colour

A

Spectral signature is blue, red & green
- appears as true color: closest to visible spectrum

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6
Q

False color Infrared

A
  • Green, red, near infrared
    Vegetation reflects infrared
  • Red plants, reflection increases or decreases based on health of plant species
  • closest to what ultraviolet light would look like
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7
Q

3 types of air photos ( viewing angles)

A
  1. Vertical
  2. Low- Oblique
  3. High Oblique
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8
Q

what is a vertical photo angle

A

Vertical: optical axis of camera at nadir (directly down, perpendicular to the surface)
- can be used for photogrammetry
- scale is constant; creation of maps; directions can be measured
- stereoscopy is possible

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9
Q

What is an oblique photo angle

A

Oblique: Larger area covered than single vertical photo
- views are distorted
- typically a supplement to vertical photos

Low-Oblique: Camera Axis inclined about 30*
- only surface
High Oblique: Camera Axis about 60* form vertical
- sky, horizon, and surface

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10
Q

What annotations are on a analog or digital image

A

Analog:
- PP: principle point (directly under camera)
- greyscale: determines proper exposure
- fiducial mark (top of y axis/ camera)
- focal length
- clock
- lens serial number
- frame number

Digital: metadata found in Exchangeable Image File Format (EXIF)

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11
Q

What is a stereo pair

A

overlapping images:
A difference in perspective, created using multiple photos along a flightline enables stereo (3D) viewing.

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12
Q

What is the stereoscopic view

A

monocular vision vs depth perception

When brain relates 2 slightly different yet overlapping images to create depth perception
- we can use stereoscope on 2 similar images to create depth

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13
Q

In a stereo pair how much overlap must occur?

A

60% rule of thumb

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14
Q

What is stereoscopic parallax (parallactic angle)

A

The same object will appear on two or more of the photos, but from slightly different viewing angle = stereoscpoic paralax

  • Parallactic angle: the optical axes of the eyes converge on a point
    • Brain relates D with PA and defines depth perception
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15
Q

Why is stereoscopic viewing used in RS

A
  • Exposure positions substitute for eye positions
  • understand how shadows impact data sense
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16
Q

Why is Air photo interpretation essential

A
  • information extraction from an image
  • based on intended application (land use, glacial retreat)
  • interpreter uses own knowledge + ability to recognize scene elements
17
Q

what is a selective key (photo interpretation)

A
  • select example that most closely corresponds to the object being identified
  • Examples: industrial buildings, residential subdivisions, park (environments that are familiar or relatable)
18
Q

What is an elimination key (photo interpretation)

A
  • step process that leads to eliminatio of all items except those being identifies
  • less common
19
Q

8 Factors in Identifying features (photo interpretive elements)

A
  • Shape
    ▪ Pattern
    ▪ Size
    ▪ Tone (color)
    ▪ Shadow
    ▪ Texture
    ▪ Association (site)
    ▪ Time
20
Q

What is Shape

A
  • form or configuration of an object
  • regular, uniform shapes typically indicate human involvement
  • example: crop circles, river meanders
    • linear, curvilinear, circular, elliptical, radial, square, rectangular
    • Curvilinear roads
21
Q

What is Pattern

A
  • Overall Spatial form of related features (groups)
  • Spatial form or arrangement of objects
  • Example: Row crops
    • dendritic, random, systemic, radiating
22
Q

What is Size

A
  • measure of an objects surface area
    • absolute: area, length, width, perimeter (knowledge of scale)
    • Relative: small, medium large
23
Q

What is Tone

A
  • Color characteristics relative to other objects
  • Used to identify features
  • relative to characteristics of objects, film or sensor type, sunlight, and choice of display
  • each feature will have a unique spectral signature
24
Q

What is shadows

A
  • can provide information about height shape, orientations
  • qualitative context
  • longer the shadow= higher the object
25
Q

What is Texture

A
  • visual impression of coarseness or smoothness caused by variability or uniformity of image tone/color
    • Aquatic environments will have smoother look than vegetation
  • uniformity between pixels (spatial change)
26
Q

What is Association

A

associating the presence of one object with another or relating it to its environment

27
Q

What is Time

A

time-series of photos can be helpful in determining the historical change of an area

  • change analysis

Remote Sensing (5 decks)

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