HR: 1340h
AN: SF53A-0723    [Abstracts]
TI: Soil Moisture and Vegetation Effects on GPS Reflectivity From Land
AU: * Torres, O
EM: omar.torres-1@nasa.gov
AF: NASA Langley Research Center, 100 NASA Road, Hampton, VA 23693 United States
AU: Grant, M S
EM: michael.s.grant@nasa.gov
AF: NASA Langley Research Center, 100 NASA Road, Hampton, VA 23693 United States
AU: Bosch, D
EM: dbosch@tifton.uga.edu
AF: US Department of Agriculture, PO Box 946 Agricultural Research Service Southeast Watershed Research Unit, Tifton, GA 31793 United States
AB: While originally designed as a navigation system, the GPS signal has been used to achieve a number of useful scientific measurements. One of these measurements utilizes the reflection of the GPS signal from land to determine soil moisture. The study of GPS reflections is based on a bistatic configuration that utilizes forward reflection from the surface. The strength of the GPS signal varies in proportion to surface parameters such as soil moisture, soil type, vegetation cover, and topography. This paper focuses on the effects of soil water content and vegetation cover on the surface based around a reflectivity. A two-part method for calibrating the GPS reflectivity was developed that permits the comparison of the data with surface parameters. The first part of the method relieves the direct signal from any multipath effects, the second part is an over-water calibration that yields a reflectivity independent of the transmitting satellite. The sensitivity of the GPS signal to water in the soil is shown by presenting the increase in reflectivity after rain as compared to before rain. The effect of vegetation on the reflected signal is also presented by the inclusion of leaf area index as a fading parameter in the reflected signal from corn and soy bean fields. The results are compared to extensive surface measurements made as part of the Soil Moisture Experiment 2002 (SMEX 2002) in Iowa and SMEX 2003 in Georgia.
DE: 1829 Groundwater hydrology
DE: 1866 Soil moisture
DE: 0933 Remote sensing
SC: Special Focus: Advances in Data Acquisition, Management, Analysis and Display [SF]
MN: 2004 AGU Fall Meeting