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REMOTE SENSING > MIDTERM > Flashcards

MIDTERM Flashcards

1
Q

the three major components of geospatial technologies

A

GIS
GPS
remote sensing

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2
Q

scientific method

A

systematic way of gathering information and answering questions

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3
Q

seven steps of the scientific method

A

identify the problem
form a hypothesis
make observations/perform experiments
do experiments and observations support hypothesis
organize and analyze data
draw conclusions
communicate results

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4
Q

in situ data collection

A

when a measurement is taken in the same place where the phenomenon is occurring

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5
Q

examples of in situ data collection

A

GPS unit
thermometer
spectral radiometer

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6
Q

the two distinct ways in which remotely sensed data must be calibrated

A

1) geometrically (x, y, z) and radiometrically (% reflectance) so that data obtained on different dates can be compared
2) calibrated with what is on the ground in terms of environmental, biophysical or cultural characteristics

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7
Q

three types of remote sensing

A

satellite
aerial photography
UAS (drones)

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8
Q

the two attributes of instantaneous field of view

A

solid angle (3 dimensional cone) - a measure of how large the object appears to a sensor looking from that point
altitude above ground - vertical distance between the object and the sensor

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9
Q

the two types of remote sensing platforms

A

orbital (satellite) and suborbital (aircraft/UAS)

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10
Q

the two types of remote sensing instruments

A

passive (external source of energy, such as reflected solar radiation) and active (sends a pulse of energy from the sensor to the object)

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11
Q

platform and instrument best for measuring 30 year change in amazon forest

A

orbital platform and passive instrument

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12
Q

platform and instrument best for monitoring environmental impact of construction site

A

suborbital platform and passive instrument

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13
Q

platform and instrument best for seeing backside of moon

A

orbital platform and active instrument

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14
Q

examples of passive sensors

A

landsat
terra
aster

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15
Q

examples of active sensors

A

lidar
sar

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16
Q

why is remote sensing a science

A

science is the broad field of human knowledge concerned with facts held together by rules
sciences include math and logic, physical sciences, biological sciences, social sciences and remote sensing is involved in all of these

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17
Q

what is remote sensing

A

the use of remote sensors to detect and measure the amount of electromagnetic radiation exiting an object or geographic area from a distance and then extracting valuable information from the data using math and stats based algorithms

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18
Q

what is as the core of geospatial technologies

A

GIScience

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19
Q

why is remote sensing an art and a science

A

it combines scientific knowledge with real world analyst experience

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20
Q

advantages of remote sensing

A

provides new scientific information
can be obtained systematically over very large areas (satellite only)
unobtrusive (but lidar can disturb environment because it sends out laser pulses)

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21
Q

limitations of remote sensing

A

not a panacea
human method-produced error may be introduced
some remote sensing systems can be intrusive
instruments may become uncalibrated
data can be very expensive to collect and analyze

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22
Q

camera obscura

A

a dark box with a small hole that lets in light to produce an upside down and backwards image on the opposing wall

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23
Q

year and inventor of the first photograph

A

1826 and Joseph Nicéphore Niépce

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24
Q

year, name, and inventor of first commercially successful camera

A

1839, daguerreotype, Louis Daguerre

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25
Q

year, name, and inventor of first consumer camera

A

1888, Kodak, George Eastman

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26
Q

how was Kodak camera different

A

affordable, roll film could be taken to be developed

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27
Q

first known surviving aerial photograph

A

Tournachon (Nadar) via tethered balloon

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28
Q

inventors of world’s first successful
motor operated airplane in 1903

A

Wright brothers

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29
Q

origins of using remote sensing

A

military photo reconnaissance during
WWI and WWII

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30
Q

U2 aerial reconnaissance
program

A

used during cold war
very difficult to fly

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31
Q

Lockheed SR 71 “Blackbird”

A

flew higher and faster than U2

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32
Q

NASA’s Earth Observing System (EOS)

A

series of polar orbiting and low inclination satellites for long term global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans

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33
Q

Unmanned Aircraft System (UAS)

A

a reconnaissance aircraft that is piloted from the ground via remote control

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34
Q

false color composite

A

created by putting the near infrared band
image in the red channel, the red band image in the green channel, and the green band image in the blue channel
can highlight vegetation

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35
Q

what is energy

A

the ability to do work

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36
Q

the six basic forms of energy

A

Chemical
Electrical
Nuclear
Thermal
Radiant
Mechanical

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37
Q

the three forms of energy transfer

A

conduction
convection
radiation

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38
Q

conduction

A

requires DIRECT CONTACT
temperature difference - frying pan on burner

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39
Q

convection

A

the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder, denser material to sink under the influence of gravity, which consequently results in transfer of heat

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40
Q

radiation

A

transfer of heat without any physical contact between objects

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41
Q

which form of energy transfer is the fastest

A

radiation

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42
Q

how solar energy is transferred

A

electromagnetic radiation

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43
Q

why EMR is of interest in remote sensing

A

does not need a medium to occur
can propagate in a vacuum space such as the space between earth and sun at the speed of light

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44
Q

how EMR travels

A

waves

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45
Q

the two parameters that describe an EMR wave

A

wavelength
frequency

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46
Q

wavelength

A

the distance between two adjacent crests or troughs
measured in micrometers (µm) or nanometers (nm)

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47
Q

frequency

A

the number of wavelengths that pass a point per unit time
1 Hertz = 1 wavelength/second

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48
Q

wavelength and frequency have an _______ relationship

A

inverse
as frequency increases, wavelength decreases

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49
Q

the speed of an EM wave

A

the speed of light

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50
Q

quantum theory of EMR

A

energy is transferred in discrete packets of particles called quanta or photons

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51
Q

photoelectric effect

A

is the emission of electrons when EMR hits a material

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52
Q

Stefan Boltzmann Law

A

the amount of energy any object radiates per unit area is a function of its surface temp

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53
Q

the electromagnetic spectrum

A

used to examine the properties of EMR in relation to wavelength

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54
Q

EM spectrum in order of increasing wavelength

A

radio
microwave
infrared
visible
ultraviolet
x-rays
gamma rays
Raging Martians Invaded Venus Using X-ray Guns

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55
Q

band

A

the spectral region of EMR wavelengths measured by a remote sensing device

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56
Q

if wavelength increases, frequency decreases and energy _______

A

decreases

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57
Q

if wavelength decreases, frequency increases and energy _______

A

increases

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58
Q

TRUE/FALSE
there is no clear cut dividing line between one spectral region and the next

A

TRUE

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59
Q

Wien’s Displacement Law

A

states that the radiation emitted by a blackbody peaks at a wavelength that is inversely proportional to the temperature

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60
Q

blackbody

A

a theoretically idealized physical body that absorbs all incident EMR and does not reflect any

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61
Q

Re: blackbody peak radiation – as temperature increases, dominant wavelength shifts toward the ______ wavelength (_____ frequency)

A

short, high

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62
Q

As temperature increases, radiation increases in a ______ shape (Stefan Boltzmann Law)

A

exponential

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63
Q

four distinct layers of the atmosphere in order from bottom to top

A

troposphere
stratosphere
mesosphere
thermosphere

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64
Q

in the troposphere, temperature _____ as altitude increases

A

decreases

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65
Q

the most active zone of the atmosphere is the ______

A

troposphere

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66
Q

environmental lapse rate in troposphere

A

temperature decreases 6.5°C per kilometer of altitude increase

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67
Q

the stratosphere contains the _____, which filters UV radiation from the sun

A

ozone layer

68
Q

commercial jets fly in the _______ because there is _______

A

stratosphere, calm air and fuel efficiency

69
Q

the coldest layer of the atmosphere is the ________

A

mesosphere

70
Q

ionization occurs in the ____ layer of the atmosphere

A

mesosphere

71
Q

in the thermosphere, gas molecules are _______ therefore there is no ______

A

far apart, heat exchange

72
Q

auroras occur in the ______ layer of the atmosphere

A

thermosphere

73
Q

99% of the atmosphere is made up of ________

A

nitrogen
oxygen
argon

74
Q

____ percent of total incoming solar radiation (direct and indirect) reaches the earth’s surface

A

45

75
Q

the troposphere is heated by _____ radiation emitted from the earth

A

longwave

76
Q

the sun emits _____ radiation while the earth emits _____ radiation

A

shortwave, longwave

77
Q

radiation budget

A

the balance between incoming radiation (shortwave) from the sun and outgoing radiation (longwave) from the earth

78
Q

for the radiation budget to be balanced, net radiation must be _____

A

zero

79
Q

four ways in which solar radiation interacts with earth’s atmosphere

A

refraction
absorption
scattering
reflection

80
Q

refraction is the ______ of light due to differing ______ and _______

A

bending, densities, speed of light

81
Q

because of ______, when we look at the sun, the perceived position is ______ than its true position

A

refraction, higher

82
Q

Snell’s law

A

used to calculate how much bending will take place based on the angle of incidence and the optical density of each substance

83
Q

absorption

A

process by which EMR is absorbed by the atmospheric particles and converted into other forms of energy

84
Q

absorption band

A

range of wavelengths in the spectrum within which radiant energy is absorbed by substances such as water (H2O), carbon dioxide (CO2), oxygen (O2)

85
Q

atmospheric window

A

atmosphere essentially closes down in certain portions of the spectrum and thus remote sensing can operate

86
Q

scattering

A

when EMR hits atmospheric particles and is redirected back out in random directions

87
Q

when diameter of atmospheric particle is less than the EMR wavelength, ___________ scattering occurs

A

Rayleigh

88
Q

when diameter of atmospheric particle is equal to the EMR wavelength, ___________ scattering occurs

A

Mie

89
Q

when diameter of atmospheric particle is greater than the EMR wavelength, ___________ scattering occurs

A

non-selective

90
Q

______ scattering is responsible for blue sky and orange/red sunrise/sunset

A

Rayleigh

91
Q

The _____ band is scattered the most because it has the _____ wavelength

A

blue, shortest

92
Q

_____ scattering causes a hazy/orangish look due to smoke and dust

A

Mie

93
Q

___________ scattering is why clouds are white because all wavelengths being scattered equally

A

Non-selective

94
Q

reflection

A

change in direction of EMR at an interface between two different media

95
Q

reflection is different from scattering because the direction is _______

A

predictable

96
Q

Specular reflection

A

angle of incidence = angle of exitance
(flat surface)

97
Q

Diffuse reflection

A

EMR is reflected at many angles
(rough surface)

98
Q

in remote sensing we are most interested in _______ reflection because it contains information about the color of the reflecting surface

A

diffuse

99
Q

a ________ is the ideal diffuse reflector

A

lambertian surface

100
Q

sunsets and sunrises appear red because sunlight is traveling a _____ distance and red light is scattered the _____

A

longer, least

101
Q

radiant flux

A

radiant energy per unit time (Watts)

102
Q

the total amount of incident radiant flux is called

A

insolation

103
Q

irradiance

A

radiant flux per unit area (W/m^2)

104
Q

radiation budget equation

A

total irradiance = radiant flux (reflected) + radiant flux (absorbed) + radiant flux (transmitted)

105
Q

reflectance

A

ratio of radiant flux reflected and total irradiance

106
Q

radiance

A

radiant flux per solid angle and per projected unit

107
Q

___________ is the most important measurement in remote sensing

A

radiance

108
Q

spectral signature plot

A

wavelength on x axis and reflectance on y axis

109
Q

spectral signature is a ________ for an object

A

unique identifier

110
Q

natural grass and artificial turf have the same reflectance in the ____ spectrum but natural grass has much higher reflectance in the ______ portion of the spectrum

A

visible, NIR

111
Q

why can blue band images appear hazy

A

scattering due to shorter wavelength (Rayleigh)

112
Q

four types of remote sensing resolution

A

spatial
temporal
spectral
radiometric

113
Q

A ______ is the smallest unit of a digital image

A

pixel

114
Q

spatial resolution

A

a measure of the smallest ground object that can be detected by the remote sensor

115
Q

temporal resolution

A

how often sensor acquires data of the same location

116
Q

spectral resolution

A

the number of bands and size of specific wavelength intervals
the more bands you have, the narrower they are

117
Q

radiometric resolution

A

the sensitivity of remote sensing detectors to small differences in electromagnetic energy
also called pixel depth

118
Q

the higher the spatial resolution, the _____ the temporal resolution

A

lower (less frequent re-visit)
if you want to see high spatial resolution, you need to fly very low, which means there is a longer revisit period

119
Q

how to compensate for the spatial/temporal tradeoff

A

more satellites

120
Q

how many bits can the human eye see

A

about 4

121
Q

Full Width at Half Maximum

A

a more precise way of stating bandwidth
we care about peak intensity even if bandwidth covers some wavelengths we don’t want

122
Q

______ is the brightest pixel value

A

255

123
Q

A ______ sensor has several, wide spectral bands

A

multispectral

124
Q

A ______ sensor has a lot of narrow bands (hundreds of spectral bands)

A

hyperspectral

125
Q

spectral resolution of human eye

A

400-700 nm (visible light)

126
Q

geostationary orbit

A

does not move at all relative to the ground
rotates at the same direction and speed as Earth
always directly over the same place on the Earth’s surface

127
Q

near polar orbit

A

north to south path wherein the satellite moves close to the North and South Poles as it makes several passes a day about Earth

128
Q

swath width

A

measurement of the width of ground the satellite can image during one pass

129
Q

the closer a satellite is to Earth, the _____ it orbits

A

faster

130
Q

geostationary (____ altitude) and sun-synchronous (____ altitude)

A

high, low

131
Q

ndvi formula

A

nir - red / nir + red

132
Q

a sun synchronous orbit always __________________

A

crosses the same area at the same local time

133
Q

the longest running enterprise for acquisition of satellite imagery of Earth

A

Landsat

134
Q

the two Landsat 8 sensors on board

A

OLI (Operational Land Imager)
TIRS (Thermal Infrared Sensor)

135
Q

Landsat uses the ________________, which divides the
entire globe into a series of paths (columns) and rows

A

Worldwide Reference System (WRS)

136
Q

which satellites carries modis sensor

A

terra and aqua

137
Q

when was terra launched

A

1999

138
Q

when was aqua launched

A

2002

139
Q

The temporal resolution for MODIS is

A

1 to 2 days

140
Q

which satellite carries aster sensor

A

terra

141
Q

the three steps of image preparation

A

layer stacking
image mosaicking
image subsetting

142
Q

layer stacking

A

stacking multiple bands into a single image file
for example for ndvi, we need red and nir stacked

143
Q

steps of layer stacking

A

make sure all image layers are acquired by same sensor at the same time
check all image layers have same spatial extent
check all layers are georectified using the same spatial reference

144
Q

image mosaicking

A

combing multiple scenes to cover entire study area

145
Q

True/False - To perform mosaicking, there must be image overlap

A

True

146
Q

different types of mosaic operators

A

minimum, maximum, mean, first/overlay, last, sum (not recommended), blend/feather (very common - uses a distance-weighted/averaging algorithm)

147
Q

image subsetting

A

getting rid of any areas that are not in study area
requires a pre-defined area of interest, such as in a shapefile

148
Q

8 elements in image interpretation

A

Tone/Color
Shape
Size/Scale
Texture
Pattern
Shadow
Site/Association
Expert/local knowledge

149
Q

The higher the satellite’s orbit, the _____ the swath width and the ______ the spatial resolution

A

wider, lower

150
Q

the narrower the swath width, the ______ the spatial resolution

A

better

151
Q

a narrow swath width leads to _____ temporal resolution

A

lower (longer revisit)

152
Q

sun-synchronous orbit is a type of ______ orbit

A

near-polar orbit

153
Q

Polar orbits are a type of _____ Earth orbit

A

low

154
Q

GPS uses a ______ earth orbit

A

medium

155
Q

when was first landsat launched

A

1972

156
Q

Watts are are equivalent to

A

Joules/second

157
Q

Radiation occurs from all objects at temperature ______

A

> 0 K

158
Q

The electromagnetic wave consists of _____ fluctuating fields

A

two

159
Q

Before quanta/photon theory, light was thought of as

A

a smooth and continuous wave

160
Q

altitude of troposphere

A

sea level –12 km

161
Q

altitude of stratosphere

A

12 –50 km

162
Q

altitude of mesosphere

A

50 –80 km

163
Q

meteors burn up in the _____ layer

A

mesosphere

164
Q

altitude of thermosphere

A

80 –480 km

165
Q

The greater the amount of smoke and dust particles in
the atmosphere, the more ________light will be
scattered away, and only the _______ light will finally reach our eyes

A

violet and blue, longer orange and red
wavelength

REMOTE SENSING (2 decks)

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