BRDF Applications in Semiarid Grassland Monitoring with the AVHRRs

Impact of BRDF on AVHRR Channel 1 and 2 reflectance :
Low Separability Afforded by 21 Orbits of AVHRR LAC/HRPT Uncorrected for BRDF Effects
(acquired over a 17-day period).

Atmospherically-corrected AVHRR VIS and NIR reflectances from grassland field survey sites in Xilingol Aimag, Inner Mongolia P.R.C.

The scatterplot above shows atmospherically-corrected reflectances from the ground resolution elements closest to field survey sites from 21 orbits acquired during the period 3rd to 19th August 1996 (four LAC scenes from NOAA-12 downloaded from the NOAA Satellite Active Archive and 17 HRPT scenes from NOAA-14, acquired at the Institute for Remote Sensing Applications in Beijing). The sites are called "FieldAngle" to distinguish them from the sites where nadir-view radiometry was carried out. For off-nadir radiometry (data not shown here), 4-channel a Milton radiometer was used atop a 4 metre mast which was tilted from 40 degrees in the backscattering direction to 40 degrees in the forward-scattering direction, close to the principal plane (the plane made by the target, the sensor and the sun) in this way.

Sampling Sites

The sites are coded as :

Their locations can be seen on this map.
More detailed information on the grassland types is here.
Click on the "Site XX" links to see photographs of the sites.
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