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geog 2735 > final exam > Flashcards

final exam Flashcards

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1
Q

what is remote sensing

A

collecting information related to electromagnetic energy reflected or emitted by a target on the ground from a considerable distance away

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2
Q

who used a camera obscura, what is that

A

Al Hazen, pinhole camera

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3
Q

who created the first photograph

A

Joseph Niépce

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4
Q

what are stereoscopes

A

use two pictures of the same scene with a slight offset mounted side-by-side to give the impression of a 3D image

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5
Q

who took the first aerial photograph of Paris

A

Gasper Felix Tournachon, aka Nadar

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6
Q

who took the first aerial photograph with a kite

A

Arthur Batut, the father of kite photography

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7
Q

T/F pigeons were used to take aerial photogaphs

A

true: 1903 bavarian pigeon corps

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8
Q

who organized the first experimental survey of Ottawa

A

the air board

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9
Q

what was the first image in Canada

A

swampy section of the slave river

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10
Q

t/f canadian crews have flown in every continent

A

true

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11
Q

describe imaging problems associated with aerial photography and their solutions

A
  1. plane moving forward; forward motion compensation
  2. turbulence causing plane to pitch and roll; gyro-stabilized mounts
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12
Q

why does image distortion happen in aerial imagery? what is the principal point, relief displacement, orthorectification, trye orthophotos

A

don’t have the same scale throughout the image

principal point: center of photo, least distortion

relief displacement: causes tall objects to lean away from the pp towards edges of photo

orthorectification: removes the effects of terrain and relief displacement to create orthophotos with uniform scale

true orthophotos: provides appearance of looking straight down on all objects

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13
Q

describe the 3 types of aerial photographs

A
  1. vertical photographs; < 3% tilt, reduces image distortion, nearly constant scale
  2. low-oblique photographs: > 3% tilt but the horizon is not visible, creates familiar perspective, scale distorted
  3. high-oblique photographs; only used for artistic reasons
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14
Q

describe panchromatic, colour imagery and colour-infrared

A

panchromatic: creates greyscale images, only uses portion of visible light spectrum

colour imagery: create true colour composites, captures red, green and blue light

colour-infrared: captures infrared light not visible, useful for environmental studies such as vegetation health

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15
Q

define parallax

A

the difference in the apparent position of an object viewed from two different positions

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16
Q

what is nadir

A

the point or line directly below the collection instrument

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17
Q

which 3 photos are plotted on national topographic system maps?

A

first, last and every 5th photo

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18
Q

define stereo pair, what do they create

A

images overlap creating two different viewpoints, or image parallax -> on stereoscopes

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19
Q

relate fiducial marks and the principal point

A

the principal point is the intersection of fiducial marks

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20
Q

is the principal point the same as nadir?

A

no, the 3% tilt means we aren’t necessarily looking at nadir

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21
Q

what is the conjugate principal point

A

the location of the PP from one photo to the adjacent photo in the flight line

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22
Q

determining scale questions
- focal length of camera lens and flight height
distance in photograph to ground

A
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23
Q

t/f tilt can cause variation in scale

A

true

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24
Q

what are some ways to interprate visual images

A
  • pattern
  • site and association
  • size
  • shadow
  • shape
  • texture
  • tone; intensity/brightness
  • time
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25
what is the remote sensing data cycle
1. energy source 2. atmospheric interaction 3. interaction with target 4. recording information 5. processing 6. analysis 7. application
26
differentiate passive vs active remote sensing
both energy source passive: sensors that measure and record electromagnetic energy reflected or emitted by the surface; sun is E source active: sensor that generates E, emits towards a target and measures the return value; lidar and radar
27
define electromagnetic energy
flow of E at the speed of light through free space
28
define wavelength, amplitude and frequency
wavelength: distance between crests of two waves, um or nm frequency: number of cycles of a wave past a fixed point, Hz (inversely related to wavelength) amplitude: maximum strength of electric and magnetic fields; intensity of the wave (no relationship with wavelength)
29
t/f a short wavelength is low frequency
false: a short wavelength is high frequency
30
what is the electromagnetic spectrum
used to examine the properties of energy in relation to the wavelength
31
define black and white body
black body: absorbs all incoming E, emits radiation based on T white body: perfect diffuse reflectors
32
what is wein's law
the peak wavelength of radiation emission is inversely related to the temperature of the emitting body; as an object gets hotter, it emits shorter wavelengths
33
what is the stefan-boltzmann constant?
in a black body, the total intensity radiated over all wavelengths increases with T
34
what is planck's law
as T increases, more light is emitted in all wavelengths
35
peak radiation emitted by the sun/earth is short/long wave radiation
sun; short earth; long
36
what portion of EM spectrum is visible light
400 to 700 nanometres
37
t/f gasses in the atmosphere can absorb or scatter incoming solar radiation
true
38
E interacts with the atmosphere and can be which 3 things?
transmitted, absorbed, scattered
39
define atmospheric scattering, mie scattering, nonselective scattering and rayleigh scattering. what does it depend on?
atmospheric scattering: redirection of EM E when it hits particles or gas molecules; occurs as E passes through atmosphere it depends on: size of wavelength in relation to scattering particle; distance travelled through scattering medium; density of scattering medium rayleigh scattering: scattering of light by particles smaller than the wavelength being scattered; makes the sky blue; has greatest impact on shorter wavelengths - at sunrise/set light travels further and results in increased scattering in red band mie scattering: scattering of light caused by atmospheric particles about the same size as the sactter wavelength; affects loner wavelengths nonselective scattering: scattering of light caused by a particle larger than the wavelength being scattered; causes clouds and fog to appear white
40
define atmospheric windows; what do ozone, CO2, water vapour
wavelengths where most of the E passes through the atmosphere; visible spectrum corresponds with an atmospheric window 03: UV CO2: far infrared; traps heat in atmosphere water vapour: longwave and shortwave between 22micrometres and 1m
41
reflection can be classified in which two ways? define them
specular reflection: from smooth surfaces that produce a single, clear reflection diffuse reflection: rough surfaces that reflect light in multiple directions
42
define incident E
total amount of E per wavelength that interacts with an object
43
define spectral signature
unique identifier for a particular item generated by charting the reflected E per wavelength
44
differentiate vegetation reflectance when its healthy vs not
healthy: chlorophyll absorbs red and blue wavelengths, strongly reflects NIR since green wavelengths have higher reflectance not: less reflection of green/nir, more red and blue which results in yellow/reddish appearance
45
what's radiometric corrections
correcting for sensor irregularities, unwanted sensor noise or atmospheric noise
46
what's an image mosaic
composite images consist of at least two images
47
what's contrast enhancement
changing original values so that more of the available range is used
48
contrast refers to?
difference in luminance or colour
49
what's an image histogram
graphical representation of the brightness values that comprise an image
50
linear contrast stretch vs histogram equalization stretch
linear contrast stretch: identifies min and max and stretches to fill new range histogram equalization stretch: assigns more values to frequently occurring portions of histogram
51
high vs low spatial frequency spatial filtering
high: data looks sharp and contains more detail low: data looks smooth or blurry
52
edge detection filters vs directional filter
edge detection filters: highlights linear features directional filter: highlights features in a specific direction
53
spectral vs information classes
spectral: groups of pixels that are uniform with respect to their brightness information: categories of interest
54
pros and cons of unsupervised pixel bases classification
pros: simple cons: not intuitive, under or over classified
55
pros and cons of supervised pixel bases classification
pros: control, high accuracy cons: human bias, dependent on training quality
56
define spatial resolution
smallest unit of area the sensor can collect information about
57
define digital number
energy used in a single pixel according to a predetermined scale, measures radiance
58
define radiometric resolution
sensor's ability to determine fine differences in E measurements
59
panchromatic vs colour composite (true, false, standard false)
panchromatic: sensor that measures visible spectrum as one band -> black and white image colour composite: displays DNs as red, green and blue true: red is red and so on false: distribution is different than true standard false: NIR is red, red is green and green is blue
60
spectral resolution vs multispectral vs hyperspectral
spectral resolution: number and width of bands measured by a sensor multispectral: 3-10 wider bands hyperspectral: hundreds of narrow bands
61
what are sounders
sensors that measure atmosphere consitions in 3 dimensions
62
this is the interval of time between observation of the same point on earth by a satellite
revisit time
63
what is an orbit that matches the speed and direction of earth's rotation
geostationary orbit
64
what is sun synchronous orbit
orbital path set so the satellite crosses the same area at the same local time
65
define satellite swath width
wdith of ground area a satellite images
66
across-track vs along-track scanners
across: rotating mirror, moves back and forth along: linear area
67

geog 2735 (2 decks)

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