Intro South Africa day1

Quick Review of Remote SensingBasic TheoryPaolo AntonelliCIMSSUniversity of Wisconsin-MadisonSouth Africa, April 2006: 

Quick Review of Remote Sensing Basic Theory Paolo Antonelli CIMSS University of Wisconsin-Madison South Africa, April 2006

Outline: 

Outline Visible: RGB, Radiance and Reflectance Near Infrared: Absorption Infrared: Radiance and Brightness Temperature

Slide3: 

Visible (Reflective Bands) Infrared (Emissive Bands)

Sensor Geometry: 

Sensor Geometry Sensor Optics Electronics

Slide5: 

Terminology of radiant energy Energy from the Earth Atmosphere

Slide6: 

Definitions of Radiation __________________________________________________________________ QUANTITY SYMBOL UNITS __________________________________________________________________ Energy dQ Joules Flux dQ/dt Joules/sec = Watts Irradiance dQ/dt/dA Watts/meter2 Monochromatic dQ/dt/dA/d W/m2/micron Irradiance or dQ/dt/dA/d W/m2/cm-1 Radiance dQ/dt/dA/d/d W/m2/micron/ster or dQ/dt/dA/d/d W/m2/cm-1/ster __________________________________________________________________

Visible: Reflective Bands: 

Visible: Reflective Bands Used to observe solar energy reflected by the Earth system in the: Visible between .4 and .7 µm NIR between .7 and 3 µm About 99% of the energy observed between 0 and 4 µm is solar reflected energy Only 1% is observed above 4 µm

Slide13: 

Radiances On Same Color Scale

Reflectance: 

Reflectance To properly compare different reflective channels we need to convert observed radiance into a target physical property In the visible and near infrared this is done through the ratio of the observed radiance divided by the incoming energy at the top of the atmosphere The physical quantity is the Reflectance i.e. the fraction of solar energy reflected by the observed target

Slide16: 

Soil Vegetation Snow Ocean

Slide17: 

Reflectances On Same Color Scale

Slide19: 

Radiance observed In the Blue Band At 0.41 µm More than 75% of the Observed energy Over Ocean In the blue bands Is due to atmospheric Scattering. Less than 25% is due to Water Leaving Energy

Slide20: 

Band 4 (0.56 Micron) Band 1 Band 4 Band 3 Transects of Reflectance

Slide22: 

Band 20 1.38 micron Strong H20

Slide23: 

Only High Clouds Are Visible

Slide24: 

Band 20 1.38 micron

Slide25: 

Visible (Reflective Bands) Infrared (Emissive Bands)

Emissive Bands: 

Emissive Bands Used to observe terrestrial energy emitted by the Earth system in the IR between 4 and 15 µm About 99% of the energy observed in this range is emitted by the Earth Only 1% is observed below 4 µm At 4 µm the solar reflected energy can significantly affect the observations of the Earth emitted energy

Slide27: 

Spectral Characteristics of Energy Sources and Sensing Systems IR 4 µm 11 µm

Observed Radiance at 4 micron: 

Observed Radiance at 4 micron Range [0.2 1.7] Values over land Larger than over water Reflected Solar everywhere Stronger over Sunglint Window Channel: little atmospheric absorption surface features clearly visible

Observed Radiance at 11 micron: 

Observed Radiance at 11 micron Range [2 13] Values over land Larger than over water Undetectable Reflected Solar Even over Sunglint Window Channel: little atmospheric absorption surface features clearly visible

Brightness Temperature: 

Brightness Temperature To properly compare different emissive channels we need to convert observed radiance into a target physical property In the Infrared this is done through the Planck function The physical quantity is the Brightness Temperature i.e. the Temperature of a black body emitting the observed radiance

Observed BT at 4 micron: 

Observed BT at 4 micron Range [250 335] Values over land Larger than over water Reflected Solar everywhere Stronger over Sunglint Window Channel: little atmospheric absorption surface features clearly visible Clouds are cold

Observed BT at 11 micron: 

Observed BT at 11 micron Range [220 320] Values over land Larger than over water Undetectable Reflected Solar Even over Sunglint Window Channel: little atmospheric absorption surface features clearly visible Clouds are cold

Conclusions: 

Conclusions Radiance is the Energy Flux (emitted and/or reflected by the Earth) which strikes the Detector Area at a given Spectral Wavelength (wavenumber) over a Solid Angle on the Earth; Reflectance is the fraction of solar energy reflected to space by the target; Given an observed radiance, the Brightness Temperature is the temperature, in Kelvin, of a blackbody that emits the observed radiance; Knowing the spectral reflective (Vis) and emissive (IR) properties (spectral signatures) of different targets it is possible to detect: clouds, cloud properties, vegetation, fires, ice and snow, ocean color, land and ocean surface temperature ……