A GPS receiver measures signal strength or signal to noise ratio (SNR). The main part of SNR is the direct signal. This is shown in black in Figure 1. It is low at the beginning of the arc, rising to ~55 db Hz at its peak, then slowly decaying again. The oscillations seen at the beginning and end of the satellite arc are caused by the interference of the direct and reflected GPS signals. The frequency of the interference tells you how far the antenna is above the reflecting surface. You can see in the example below (the Oklahoma SMAP in situ testbed) that the 6-meter antenna has higher frequency SNR data than the 2.5-meter antenna.
Last modified: 2019-12-26 16:24:59 America/Denver
The site was originally developed by the GPS Reflections Research Group at the University of Colorado (CU) using funding from NSF EAR1144221. It was built by Evan Pugh and Kristine Larson at CU and by the UNAVCO Education and Community Engagement Program.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, NASA, UNAVCO, or CU.