摘要：How well can GPS signals penetrate avalanche snow?
A: Surprisingly, GPS signals penetrate avalanche snow very well.
Because snow is in part composed of frozen water, many people assume that snow has signal attenuation properties similar to liquid water. Tests have shown that even a high sensitivity GPS receiver cannot track through more than 1 to 2 millimeters of water where the majority of the GPS signal is reflected at interfaces between materials. Two such interfaces exist: an air-water interface at the surface of the water and the water-air interface around the submerged receiver antenna, which reflects what remains of the signal. Some of the attenuation is due to dielectric losses, but the majority is due to the air-water reflection.
What happens, however, when the GPS signal encounters snow?
In terms of reflection, the loss is approximately 11 dB lower for snow than with liquid water. Smaller angles of incidence of the signals improve their penetration (i.e., less reflection); thus, reflection losses are highest with low elevation satellites and satellites upslope of an avalanche slide.
