Alkali flats area of White Sands. A flat, extended area of gypsum sand. High, uniform, nearly Lambertian reflectance in the visible and near infrared. Altitude 1,200 m, hence low atmospheric aerosol loading. High probability of clear weather. Very restricted ground access. Areas with human activity. Possibility of saturation in some spectral bands with high sun. Subject to soil moisture variations, high water table (can have standing water). AERONET site. White Sands National Monument (WSNM) has a long history of use as a calibration target for Earth observing instruments. The site is located in a mountain basin in south-central New Mexico. Although the area has very suitable weather conditions, with many clear days, the calibration site is not ideal because its reflectance is greatly affected by changes in soil moisture. The surface also deviates considerably from a Lambertian response at high solar and viewing zenith angles. However, the University of Arizona group uses a 500- by 500-m area at the specified coordinates known as Chuck Site, which has a near-Lambertian response. (Source: Network for Calibration and Validation of Earth Observation (NCAVEO) Web site, http://www.ncaveo.ac.uk/calibration/radiometry/in-flight/#whitesands).
Google Earth: Some pockmarks at detailed scales. Generally spatially homogeneous across an area of about 10 km (E-W) by 15 km (N-S).
U.S. Department of the Interior |
U.S. Geological Survey
