| Popis: |
The Remote Sensing Group at the University of Arizona has developed an automated methodology and instrument suite to measure the surface reflectance of the vicarious calibration test site at Railroad Valley, Nevada. Surface reflectance is a critical variable used as one of the inputs into a radiative transfer code to predict the top-of-atmosphere radiance, and inexpensive and robust ground-viewing radiometers have been present at the site since 2004. The goal of the automated approach is to retain RSG’s current 2-3% level of uncertainty while increasing the number of data sets collected throughout the year without the need for on-site personnel. A previous study was completed to determine if the number and positions of the four radiometers were adequate to spatially sample the 1-km 2 large-footprint site at Railroad Valley. The preliminary study utilized one set of panchromatic data from Digital Globe’s QuickBird satellite. Results from this one day showed that the positions of the four ground-viewing radiometers adequately sample the site. The work presented here expands in a spectral and temporal sense by using high-spatial-resolution data from Ikonos, QuickBird, and Landsat-7 ETM+ to determine if the locations of the ground-viewing radiometers correctly sample the site. The multispectral capability of these sensors is used to establish if there are any spectral effects, which will also help RSG to determine what spectral bands should be chosen for the new ground-viewing radiometers that are currently in development for the automated test site at Railroad Valley. |
