The LSpec site in Nevada was established in late 2006 to enable unattended vicarious calibration of visible and nearinfrared remote sensing instruments. The site was selected because the large, relatively undisturbed, uniform, dry lakebed is suitable as a reflectance target. LSpec data include autonomous measurements of the playa taken at near-nadir viewing conditions every five minutes throughout the day. Thus, LSpec data can be retrieved for a calibration overflight time which will account for non-zenith solar angles. However, if the sensor under test views the playa from an off-nadir geometry, the LSpec reflectance data must be corrected for the playa's bi-directional reflectance factor. A ground-based experiment was performed on July 23, 2008 to collect reflective data from the playa over a series of solar zeniths, solar azimuths, and off-nadir collection angles. The collection conditions were managed to richly sample the space of zenith and azimuth differences between the sun and sensor. Data reduction shows that it is possible to experimentally derive a bi-directional reflectance distribution from field measurements suitable to use for calibration corrections. Additionally, analysis of the experimental data demonstrates consistent results with the data collected concurrently from the LSpec insitu sensors.

Date Published: 27 April 2009
PDF: 10 pages
Proc. SPIE 7334, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XV, 733412 (27 April 2009); doi: 10.1117/12.818488

Published in SPIE Proceedings Vol. 7334:
Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XV
Sylvia S. Shen; Paul E. Lewis, Editor(s)