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21 Cards in this Set

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  • Back

Remote sensing resolutions

Resolution: resolving power, ability of an optical system to distinguish between signals that are spatially near or spectrally similar

Spectral: the number and size of spectral regions the sensor records data in (blue, green, red, infrared, microwave)

Spatial: size of field of view

Temporal: how often sensors acquire data

Radiometric: the sensitivity of detectors to small diffs in electromagnetic energy

Passive RS

radiation that eminates naturally from an object

ex: sun, Earth's surface

generally needs daylight

hyperspectral, multispectral

Active RS

system that emits energy

provides own energy source

can be used day or night

requires lots of energy

ex: Radar, LiDar, Synthetic Aperture Radar (SAR)

electromagnetic spectrum

A continuum of energy, travels at speed of light

the range of all possible frequencies from radiation


shortest wls- radio/microwaves

longest- gamma (fastest)

order: gamma, x-ray UV, visible, infrared, microwaves

regions of electromagnetic spectrum used in RS (UV, Visible, NIR, SWIR)

UV: .3-.4um


NIR: .7-1.3um; emittance energy

SWIR: 1.3-3um

Conversion of wavelengths from nanometers (nm) to micrometers (um) and vice versa

1 nm = .0001 um

so, 1 um = 1000 nm

10 nm = .01 um

100 nm = .1 um

1000 nm = 1 um

1500 nm = 1.5 um


the relationship between frequency and wavelength

frequency is inversely proportional to wavelength

so, the shorter the wavelength, the lower the frequency (and vice versa)

How are photons and wavelengths related to the detection of electromagnetic radiation?

electromagnetic energy can only be detected as it interacts with matter

a photodetector: photons interact with it and produces an electrical signal that varies in strength, proportional to # photons

measured by two fluctuating fields: electric & magnetic

wave concept

4 components of RS system

Energy Source

Transmission Path (i.e. Sun)

Target: has to bounce off something/reflector to a sensor


Relationship between an object's temp, NRG, and dominant wavelength

blackbody (theoretical substance that absorbs and radiates energy at the max possible rate per unit at each wavelength for a given temp..the perfect abosrber and emitter...

total emitted radiation is proportionate to its absolute temp (stefan-Boltzmann Law))

greater temp = greater amount of radiant energy emitted from object

as temp increases its dominant wl gets shorter

Wien's Displacement Law- determine blackbody's dominant wl

How does electromagnetic energy interact with the atmosphere and earth?

Atmosphere: Scattering (Raleigh, Mie, Nonselective)

Earth: Reflectance, absorption, transmission


wavelength dependent, mostly in upper 4.5 km of atmosphere

Scattering by particles that are smaller than the wavelength of visible and near infrared radiation...more scattering at smaller wavelengths....blue sky and red sunsets


wavelength dependent, longer wl than Raleigh, lower 4.5 km of atmosphere

Particles in the atmosphere are ~equal in size to the wavelength of the scattered radiation... influences longer wavelengths...dust, pollen, smoke...smog is reddish brown


lower portions of atmosphere

all wavelengths equally affected...particles are larger than the wavelengths...most common...water droplets in clouds...gray haze


atmosphere is preventing the transmission of radiation

Ozone (O3 and O2), Water (H2O), and Carbon Dioxide (CO2) are responsible for most of the solar radiation absorption that occurs

absorbed and re-radiated at longer wavelengths

atmospheric windows


occurs when a ray of light is re-directed as it strikes a nontransparent surface

The nature of the reflection depends on sizes of surface irregularities in relation to the wavelength of the radiation considered

- Specular Reflection: reflection off a smooth object (ie. smooth body of water, mirrors)

- Diffuse Reflection : off of rough objects (clothes, roadways, etc)


occurs when radiation is neither reflected or absorbed, but passes through a substance without significant weakening.

wave concept

explains how electromagnetic energy moves, but must interact with matter for it to be detected

atmospheric windows

what doesn't get absorbed, wavelengths that are easily transmitted

incident radiation

absorbed + reflected + transmitted radiation

law of conservation of energy

emittance energy

mainly derived from shortwave energy from sun that has been absorbed, then re-radiated at longer wavelengths

strongest at the far infrared region

reveals information about thermal properties of materials