GPS Tracking Performance Under Avalanche Deposited Snow

摘要

The tracking performance of several High Sensitivity Global Positioning System (HSGPS) receivers under avalanche deposited snow was investigated. Two field trials were held during April 2006 in the Canadian Rocky Mountains to study the factors affecting GPS signals and positioning performance. The PLAN Group at the University of Calgary has developed the miniature Global Navigation Asset Tracker (GNAT?) which integrates the SiRFstar IIe/LP or SiRFstar III GPS receivers with a microcontroller, onboard flash storage and a 2.4 GHz Zigbee modem. The test systems were placed entirely down a 6 cm borehole for 2.5 hours with position, velocity, time, status and raw observation data collected at 1 Hz. Post-mission analysis included determining GPS signal attenuation, pseudorange measurement error and availability along with single point position accuracy as they relate to the receivers depth in the snow pack. GPS Signal attenuation of approximately 1.8 dB per metre of snow penetration was measured. Methods of improving the position beneath the avalanche debris were investigated, resulting in horizontal position RMS values of 7.4 m and 2.8 m at snow depths of 2.0 and 2.68 m respectively.