MIDTERM Flashcards
1
Q
the three major components of geospatial technologies
A
GIS
GPS
remote sensing
2
Q
scientific method
A
systematic way of gathering information and answering questions
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
4
Q
in situ data collection
A
when a measurement is taken in the same place where the phenomenon is occurring
5
Q
examples of in situ data collection
A
GPS unit
thermometer
spectral radiometer
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
7
Q
three types of remote sensing
A
satellite
aerial photography
UAS (drones)
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
9
Q
the two types of remote sensing platforms
A
orbital (satellite) and suborbital (aircraft/UAS)
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)
11
Q
platform and instrument best for measuring 30 year change in amazon forest
A
orbital platform and passive instrument
12
Q
platform and instrument best for monitoring environmental impact of construction site
A
suborbital platform and passive instrument
13
Q
platform and instrument best for seeing backside of moon
A
orbital platform and active instrument
14
Q
examples of passive sensors
A
landsat
terra
aster
15
Q
examples of active sensors
A
lidar
sar
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
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
18
Q
what is as the core of geospatial technologies
A
GIScience
19
Q
why is remote sensing an art and a science
A
it combines scientific knowledge with real world analyst experience
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)
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
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
23
Q
year and inventor of the first photograph
A
1826 and Joseph Nicéphore Niépce
24
Q
year, name, and inventor of first commercially successful camera
A
1839, daguerreotype, Louis Daguerre
25
year, name, and inventor of first consumer camera
1888, Kodak, George Eastman
26
how was Kodak camera different
affordable, roll film could be taken to be developed
27
first known surviving aerial photograph
Tournachon (Nadar) via tethered balloon
28
inventors of world's first successful
motor operated airplane in 1903
Wright brothers
29
origins of using remote sensing
military photo reconnaissance during
WWI and WWII
30
U2 aerial reconnaissance
program
used during cold war
very difficult to fly
31
Lockheed SR 71 “Blackbird”
flew higher and faster than U2
32
NASA’s Earth Observing System (EOS)
series of polar orbiting and low inclination satellites for long term global observations of the land surface, biosphere, solid Earth, atmosphere, and oceans
33
Unmanned Aircraft System (UAS)
a reconnaissance aircraft that is piloted from the ground via remote control
34
false color composite
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
35
what is energy
the ability to do work
36
the six basic forms of energy
Chemical
Electrical
Nuclear
Thermal
Radiant
Mechanical
37
the three forms of energy transfer
conduction
convection
radiation
38
conduction
requires DIRECT CONTACT
temperature difference - frying pan on burner
39
convection
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
40
radiation
transfer of heat without any physical contact between objects
41
which form of energy transfer is the fastest
radiation
42
how solar energy is transferred
electromagnetic radiation
43
why EMR is of interest in remote sensing
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
44
how EMR travels
waves
45
the two parameters that describe an EMR wave
wavelength
frequency
46
wavelength
the distance between two adjacent crests or troughs
measured in micrometers (µm) or nanometers (nm)
47
frequency
the number of wavelengths that pass a point per unit time
1 Hertz = 1 wavelength/second
48
wavelength and frequency have an _______ relationship
inverse
as frequency increases, wavelength decreases
49
the speed of an EM wave
the speed of light
50
quantum theory of EMR
energy is transferred in discrete packets of particles called quanta or photons
51
photoelectric effect
is the emission of electrons when EMR hits a material
52
Stefan Boltzmann Law
the amount of energy any object radiates per unit area is a function of its surface temp
53
the electromagnetic spectrum
used to examine the properties of EMR in relation to wavelength
54
EM spectrum in order of increasing wavelength
radio
microwave
infrared
visible
ultraviolet
x-rays
gamma rays
Raging Martians Invaded Venus Using X-ray Guns
55
band
the spectral region of EMR wavelengths measured by a remote sensing device
56
if wavelength increases, frequency decreases and energy _______
decreases
57
if wavelength decreases, frequency increases and energy _______
increases
58
TRUE/FALSE
there is no clear cut dividing line between one spectral region and the next
TRUE
59
Wien’s Displacement Law
states that the radiation emitted by a blackbody peaks at a wavelength that is inversely proportional to the temperature
60
blackbody
a theoretically idealized physical body that absorbs all incident EMR and does not reflect any
61
Re: blackbody peak radiation -- as temperature increases, dominant wavelength shifts toward the ______ wavelength (_____ frequency)
short, high
62
As temperature increases, radiation increases in a ______ shape (Stefan Boltzmann Law)
exponential
63
four distinct layers of the atmosphere in order from bottom to top
troposphere
stratosphere
mesosphere
thermosphere
64
in the troposphere, temperature _____ as altitude increases
decreases
65
the most active zone of the atmosphere is the ______
troposphere
66
environmental lapse rate in troposphere
temperature decreases 6.5°C per kilometer of altitude increase
67
the stratosphere contains the _____, which filters UV radiation from the sun
ozone layer
68
commercial jets fly in the _______ because there is _______
stratosphere, calm air and fuel efficiency
69
the coldest layer of the atmosphere is the ________
mesosphere
70
ionization occurs in the ____ layer of the atmosphere
mesosphere
71
in the thermosphere, gas molecules are _______ therefore there is no ______
far apart, heat exchange
72
auroras occur in the ______ layer of the atmosphere
thermosphere
73
99% of the atmosphere is made up of ________
nitrogen
oxygen
argon
74
____ percent of total incoming solar radiation (direct and indirect) reaches the earth's surface
45
75
the troposphere is heated by _____ radiation emitted from the earth
longwave
76
the sun emits _____ radiation while the earth emits _____ radiation
shortwave, longwave
77
radiation budget
the balance between incoming radiation (shortwave) from the sun and outgoing radiation (longwave) from the earth
78
for the radiation budget to be balanced, net radiation must be _____
zero
79
four ways in which solar radiation interacts with earth's atmosphere
refraction
absorption
scattering
reflection
80
refraction is the ______ of light due to differing ______ and _______
bending, densities, speed of light
81
because of ______, when we look at the sun, the perceived position is ______ than its true position
refraction, higher
82
Snell's law
used to calculate how much bending will take place based on the angle of incidence and the optical density of each substance
83
absorption
process by which EMR is absorbed by the atmospheric particles and converted into other forms of energy
84
absorption band
range of wavelengths in the spectrum within which radiant energy is absorbed by substances such as water (H2O), carbon dioxide (CO2), oxygen (O2)
85
atmospheric window
atmosphere essentially closes down in certain portions of the spectrum and thus remote sensing can operate
86
scattering
when EMR hits atmospheric particles and is redirected back out in random directions
87
when diameter of atmospheric particle is less than the EMR wavelength, ___________ scattering occurs
Rayleigh
88
when diameter of atmospheric particle is equal to the EMR wavelength, ___________ scattering occurs
Mie
89
when diameter of atmospheric particle is greater than the EMR wavelength, ___________ scattering occurs
non-selective
90
______ scattering is responsible for blue sky and orange/red sunrise/sunset
Rayleigh
91
The _____ band is scattered the most because it has the _____ wavelength
blue, shortest
92
_____ scattering causes a hazy/orangish look due to smoke and dust
Mie
93
___________ scattering is why clouds are white because all wavelengths being scattered equally
Non-selective
94
reflection
change in direction of EMR at an interface between two different media
95
reflection is different from scattering because the direction is _______
predictable
96
Specular reflection
angle of incidence = angle of exitance
(flat surface)
97
Diffuse reflection
EMR is reflected at many angles
(rough surface)
98
in remote sensing we are most interested in _______ reflection because it contains information about the color of the reflecting surface
diffuse
99
a ________ is the ideal diffuse reflector
lambertian surface
100
sunsets and sunrises appear red because sunlight is traveling a _____ distance and red light is scattered the _____
longer, least
101
radiant flux
radiant energy per unit time (Watts)
102
the total amount of incident radiant flux is called
insolation
103
irradiance
radiant flux per unit area (W/m^2)
104
radiation budget equation
total irradiance = radiant flux (reflected) + radiant flux (absorbed) + radiant flux (transmitted)
105
reflectance
ratio of radiant flux reflected and total irradiance
106
radiance
radiant flux per solid angle and per projected unit
107
___________ is the most important measurement in remote sensing
radiance
108
spectral signature plot
wavelength on x axis and reflectance on y axis
109
spectral signature is a ________ for an object
unique identifier
110
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
visible, NIR
111
why can blue band images appear hazy
scattering due to shorter wavelength (Rayleigh)
112
four types of remote sensing resolution
spatial
temporal
spectral
radiometric
113
A ______ is the smallest unit of a digital image
pixel
114
spatial resolution
a measure of the smallest ground object that can be detected by the remote sensor
115
temporal resolution
how often sensor acquires data of the same location
116
spectral resolution
the number of bands and size of specific wavelength intervals
the more bands you have, the narrower they are
117
radiometric resolution
the sensitivity of remote sensing detectors to small differences in electromagnetic energy
also called pixel depth
118
the higher the spatial resolution, the _____ the temporal resolution
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
how to compensate for the spatial/temporal tradeoff
more satellites
120
how many bits can the human eye see
about 4
121
Full Width at Half Maximum
a more precise way of stating bandwidth
we care about peak intensity even if bandwidth covers some wavelengths we don't want
122
______ is the brightest pixel value
255
123
A ______ sensor has several, wide spectral bands
multispectral
124
A ______ sensor has a lot of narrow bands (hundreds of spectral bands)
hyperspectral
125
spectral resolution of human eye
400-700 nm (visible light)
126
geostationary orbit
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
near polar orbit
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
swath width
measurement of the width of ground the satellite can image during one pass
129
the closer a satellite is to Earth, the _____ it orbits
faster
130
geostationary (____ altitude) and sun-synchronous (____ altitude)
high, low
131
ndvi formula
nir - red / nir + red
132
a sun synchronous orbit always __________________
crosses the same area at the same local time
133
the longest running enterprise for acquisition of satellite imagery of Earth
Landsat
134
the two Landsat 8 sensors on board
OLI (Operational Land Imager)
TIRS (Thermal Infrared Sensor)
135
Landsat uses the ________________, which divides the
entire globe into a series of paths (columns) and rows
Worldwide Reference System (WRS)
136
which satellites carries modis sensor
terra and aqua
137
when was terra launched
1999
138
when was aqua launched
2002
139
The temporal resolution for MODIS is
1 to 2 days
140
which satellite carries aster sensor
terra
141
the three steps of image preparation
layer stacking
image mosaicking
image subsetting
142
layer stacking
stacking multiple bands into a single image file
for example for ndvi, we need red and nir stacked
143
steps of layer stacking
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
image mosaicking
combing multiple scenes to cover entire study area
145
True/False - To perform mosaicking, there must be image overlap
True
146
different types of mosaic operators
minimum, maximum, mean, first/overlay, last, sum (not recommended), blend/feather (very common - uses a distance-weighted/averaging algorithm)
147
image subsetting
getting rid of any areas that are not in study area
requires a pre-defined area of interest, such as in a shapefile
148
8 elements in image interpretation
Tone/Color
Shape
Size/Scale
Texture
Pattern
Shadow
Site/Association
Expert/local knowledge
149
The higher the satellite's orbit, the _____ the swath width and the ______ the spatial resolution
wider, lower
150
the narrower the swath width, the ______ the spatial resolution
better
151
a narrow swath width leads to _____ temporal resolution
lower (longer revisit)
152
sun-synchronous orbit is a type of ______ orbit
near-polar orbit
153
Polar orbits are a type of _____ Earth orbit
low
154
GPS uses a ______ earth orbit
medium
155
when was first landsat launched
1972
156
Watts are are equivalent to
Joules/second
157
Radiation occurs from all objects at temperature ______
> 0 K
158
The electromagnetic wave consists of _____ fluctuating fields
two
159
Before quanta/photon theory, light was thought of as
a smooth and continuous wave
160
altitude of troposphere
sea level –12 km
161
altitude of stratosphere
12 –50 km
162
altitude of mesosphere
50 –80 km
163
meteors burn up in the _____ layer
mesosphere
164
altitude of thermosphere
80 –480 km
165
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
violet and blue, longer orange and red
wavelength
