Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Remote Sensing Final > Final > Flashcards

Final Flashcards

1
Q

Electromagnetic Energy - Properties

A

1) Wavelength
2) Amplitude
3) Phase
4) Frequency

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Radiant Energy

A 
Q = h * v
Q = Radiant Energy
h = Planck's constant
v = Frequency
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Radiant Flux

A

Rate of transfer of the energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Radiant Flux Density

A

The amount of energy entering or leaving an object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Blackbody

A

A hypothetical entity that absorbs all radiation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Kirchhoff’s Law

A

For blackbodies the emissivity = absorption = 1
Perfect reflection emissivity = 0

e= emissivity = M/ Mb
where:
• M = emitted radiation of the real object
• Mb= emitted radiation of the blackbody @the same temperature of the real object

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Stefan-Boltzmann Law – emitted radiation

A

Mb = sT^4

Mb = Total emitted radiation in Watts/m2 (a radiant flux density)
s= Stefan-Boltzmann constant (5.67 10-8 W/m2/K4)
T = Absolute body temperature [K]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Wien’s Displacement Law - Peak of Exitance

A

lmax= 2898/T

lmax= wavelength
T = Absolute body temperature [K]
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Kirchhoff + Stefan-Boltzmann

A

For real material we use the concept of emissivity (e) to the blackbody law in order
to relate the actual radiance of a real body (greybody) at temperature T

M = esT4
M = Total emitted radiation in Watts/m2 (a radiant flux density)
s= Stefan-Boltzmann constant (5.67 10-8 W/m2/K4)
T = Absolute body temperature [K]
e= emissivity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Brightness Temperature

A

The temperature of the equivalent blackbody that would give the same radiance at the wavelength under consideration

Typically used in thermal and passive microwave RS

For sufficient long wavelengths Tb~eT

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Infrared

A 
Near Infrared (NIR) 0.7-1.3 μm
Mid Infrared (MIR) 1.3-7.0 μm
Far Infrared (TIR) 7-1000 μm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

NIR

A

Sensitive to plant’s health
Similar to VIS
Essentially solar radiation reflected from the earth’s surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Mid Infrared/SWIR

A

Soil moisture applications and veg water content
Detecting plant stress and burnt area
Can detect active fires

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Far Infrared/LWIR

A

Thermal Infrared

surface temperature, evapotranspiration, heat fluxes, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Interaction of EM Radiation

A

Absorbed
Transmitted
Reflected

“Conservation of Energy”

Sum to 1

Divide by the incident to = the proportion of 1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Scattering

A

Depends on Wavelength, Size Particles, # of Particles, Depth of the Atmosphere

Function of: radiation wavelength, particle size

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Rayleigh Scattering

A

-When the molecule diameter is smaller
than the wavelength
- Primarily caused by 02 and N2
- Scattering happens through absorption and re-emission
- Responsible for blue skies and red sunsets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Mie Scattering

A
  • Caused by larger particles with diameters approximately equal to the radiation wavelength EX. water vapor, dust, smoke
  • Causes pretty sunsets
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Absorption

A

When the atmosphere absorbs radiation

Caused by: Ozone and oxygen <300nm
Carbon dioxide 13-17.5 um (MIR & TIR)
Water vapor 5.5-7um and 27um

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Reflection

A

Product of: surface roughness, # of leaves, geometry of incident, viewing angle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Specular Reflection

A

When an object is smooth all (or almost all) of the radiation is reflected in one direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Diffuse Reflection

A

Also called Lambertian

When a surface is rough energy is reflected in every direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Bidirectional Reflectance Distribution Function (BRDF)

A

Ratio of reflected radiance to the incident irradiance of a flat surface

Describes the optical behavior of a surface with respect to angles of illumination and observation -> Hence BIdirectional (and wavelength)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Volume Scattering

A

Scattering occurring within the medium as the EMR transmits from one medium to another

EX inside of snow, between the snow particles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Albedo
The directional integration of reflectance over ALL sun and view angles and sun spectrum (VIS and NIR)
26
Atmospheric Correction
Converts measurements from description of earth-atmosphere system to of the earth's surface
27
Dark Pixel Method
Minimum Digital Number value is assumed to be atmospheric distortion and subtracted from all pixels Atmospheric Profile - Other method of Atmospheric Correction
28
Spectral Reflectance: Vegetation
- Low reflectance in VIS due to chlorophyll absorption - depends on plant health, greater jump healthier plant - High reflectance in NIR due to leaf scattering - Lower reflectance in NIR w/ dips due to water absorption - Changes because of health, physiology, and structure
29
Vegetation Indices
- The Red Edge is foundational | - Measure "greenness"
30
Simple Ratio Index
NIR/Red Larger value = healthier veg (no upper bound) Smaller value = Not veg
31
NDVI
(NIR-Red)/(NIR+Red) -1 to 1 1 = Healthy veg -1 = water <0.1 = Not veg
32
NBR | dNBR
(NIR-SWIR)/(NIR+SWIR) PrefireNBR-PostfireNBR -Sensitive to water, high severity pixels may be water, mask water before
33
Enhanced Vegetation Index (EVI)
Stabilizes aerosol influence on NDVI
34
Spectral Reflectance: Water
Low Reflectance in VIS, drops off in NIR and SWIR | Distribution of reflectance can be used to infer water contents
35
Normalized Difference Water Content
2 Types: (NIR-SWIR)/(NIR+SWIR) - for veg in drought conditions -1 to 0 = bright surface w/ no water 1 = water! (green-nir)/(green+nir) - for flood water/level changes <0.3 = No water
36
Spectral Reflectance: Snow
- Tough to distinguish from clouds -> different signatures in MIR -> cloud reflectance(x) of cloud type - High in VIS, decreases in NIR, dark on SWIR - Varies with grain size -> volumetric scattering
37
Normalized Differenced Snow Index
(R550-R1640)/(R550+R1640)
38
Spectroscopy
The study of how radiated energy and matter interact
39
Spectrometry
Deals with the measurement of a specific spectrum
40
All materials reflect, absorb or emit photons in ways characteristic of their molecular makeup
41
Multispectral Imagers
- Record incoming reflected or emitted EMR at a few wide and separated wavelengths - Typical band width is 100s of nm - Discrete bands
42
Hyperspectral Imagers
- Records EMR at a series of very narrow and contiguous bands - band width is typically 10s of nm - Continuous spectrum
43
Data Cube
-How hyperspectral data is presented Compiled from hyperspectral data, when a spectrometer collected bands as narrow as 1nm to create an image with as many bands as acquired channels
44
Hyperspectral data
- Typically very noisy - Bands are averaged to limit noise - Wider wavelength ranges increase SNR
45
Digital Image
2-D array of pixels | -Each pixel has an intensity value and location address from its row and column reference
46
Digital Number
Represents a physical quantity such as solar reflectance in a pixel - Pixel values are coded as Digital Numbers of Brightness Values - Stored with binary digits that must be converted to real numbers
47
Natural Color Model
Pros: It's what our eyes would see Cons: Blue region subject to atmospheric scattering, Instruments collect radiation across the spectrum
48
False Color Images
Cons: They look fucked up and weird Pros: Can see things invisible to our eyes normally
49
Color Infrared Image
Shows living vegetation and water bodies very clearly
50
Landsat
- 30m Spatial Res - 16 Day Temporal Res - Operational Land Imager, ETM+, Thermal IR Sensor - 8 has 9 bands
51
MODIS
- 250m-1 k spatial - aqua and terra orbit every day - 36 bands - Moderate Resolution Imaging Spectroradiometer
52
AVHRR
- 1km spatial - 4 satellites, 16 images a day - 6 bands - cloud and surface, land water boundaries, snow and ice, night cloud mapping - Advanced Very High Resolution Radiometer
53
ASTER
- Dead satellite (02-09) - 15 to 90m spatial - surface temperature, emissivity, reflectance, and elevation
54
VIIRS
- Visible Infrared Imaging Radiometer Suite - 1km spatial resolution - daily or bidaily temp res - Many bands
55
Hyperspectral Sensors
Mostly airborne | Very few satellites
55
Hyperspectral Sensors
Mostly airborne | Very few satellites
56
Hyperspectral Sensors
Mostly airborne | Very few satellites
57
Hyperion
Hyperspectral spaceborne sensor Dead Sensor (00-17) 30m spatial, 242 bands
58
Spectral Mixing
- Assumes linear mixing of various fractional land covers to form the actual measured reflectance - Finds the best fitting surface fractions of endmembers
59
LiDAR Distance Formula
Distance = (t*c)/2 ``` t = elapsed time c = speed of light ```
60
Characteristics of emitted and returned LiDAR pulses
timing of pulses, wavelength, and angles
61
Key Elements of Airborne LiDAR
1) GPS Unit 2) Inertial Measurement Units (position of aircraft) 3) Infrared or Green laser 4) Ground Control Points
62
LiDAR Observations
Range Distance and Intensity (fraction of photon returned)
63
LiDAR Return Types
Primary Returns - from the first object a pulse contacts | Secondary Returns - from the portion of a pulse that passes through a porous surface (tree canopy), 5 max
64
LiDAR: Waveform Return
- records the power of the pulse received as a function of time - Can show more info than discrete returns - Typically have larger footprints
65
Processing LiDAR Data
Gathered as a zigzag | Must be resampled, gridded, and single shots are interpolated
66
LiDAR Applications
Mapping aboveground biomass Forest heights Power line mapping
67
Thermal Region Wavelengths
3.5-20um, typically 8-13um Emitted, not reflected 3-5um lots of absorption in CO2 8-13um very little absorption in Ozone
68
Thermal RS Theory
- All objects above 0K emit radiation - Intensity and spectral composition depends on the material and its temperature - Observed radiance is a function of actual temperature and emissivity - Little atmospheric scattering - Some restrictions due to atmospheric absorption
69
Emissivity
Dependent on: Physical properties of surface: water content, density, color, roughness, compaction -wavelength, surface temperature, and angle of observation -Polarization dependent
70
Brightness Temperature
The temperature of the equivalent blackbody that would give the same radiance at the wavelength under consideration - Always lower than absolute temperature - If emissivity of an object is know, then absolute temp can be derived from the radiation an object emits - If emissivity is not known, then only brightness temp can be known
71
Thermal Inertia
Determined by thermal conductivity, thermal diffusivity, and thermal capacity -Objects with higher inertia will have a smaller diurnal range in temperature
72
Thermal RS: Example Sensors
GOES Landsat 8 AVHRR Ecostress
73
Thermal RS: Applications
Soil moisture, land surface temp, mineral mapping, ET, forest fires, Sea Surface Temperature, cloud structure
74
Microwave EM Spectrum Region
``` 1mm-1m W band (3mm) to P band (75cm) ```
75
Weather Radar Microwave
Use K band or S band
76
GPS Microwave
L-band
77
Soil Moisture
L band
78
Penetration Depth Of Microwaves
X band, C band, L band (Deepest penetration)
79
Polarization
Horizontal and vertical plane of EMR
80
Passive Microwave RS
Focuses on detecting and monitoring emissivity and temperature changes Radiometer Energy is very low so footprint must be very large
81
Active Microwave RS
Detects and monitors changes in reflectivity and backscatter | Radar
82
Dielectric Constant
water content, has an inverse relationship with emissivity
83
3 Dominant Source of Microwave Radiation
1) Earth's Surface 2) Atmosphere 3) Extraterrestrial
84
Rayleigh Jean's Expression
- Substitutes for Plank's function at higher wavelengths - Integration over microwave region shows a linear relationship with temperature - At polarization, brightness temp/MWR is a product of physical temp * emissivity
85
Radiative Transfer Model
Relative emissivity to soil moisture
86
AMSR-E 2
Advanced Microwave Scanning Radiometer Earth Observing Currently orbiting
87
SMOS
Soil Moisture Ocean Salinity | L band
88
SMAP
Soil Moisture Active Passive | Really only passive
89
GPM
Global Precipitation Measurement | 6-36km res
90
Microwave Polarization Difference Index
(Tbv-Tbh)/(Tbv+Tbh)
91
Radiative Transfer Models
Similar to MPDI, but needs more info. on temperature, microwave roughness, vegetation opacity, and scattering albedo
92
Snow Water Equivalent
- Snow depth from PMW is inaccurate - Dry snow scatters - Wet snow absorbs and emits
93
Active Microwave RS
Can have finer spatial resolution More random noise Distortion and shading issues
94
Backscatter
Indicates how much energy is scattered and reflected back to a sensor from a target object Depends on: Composition (roughness), Polarization, wavelength, Viewing angle -Increases with soil moisture and surface roughness
95
Validation
Accuracy Precision Stability
96
Sources of Error
1) Sensor Limitations 2) Method of Analysis 3) Landscape Complexity 4) Verification Process
97
Validation Steps
1) Design your sampling strategy 2) Collect reference data 3) Extract Information 4) Compare 5) Analyze the causes
98
GRACE
Gravimetry satellite detects elevation changes and areas of high gravity generally

Remote Sensing Final (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions