Satellite Telemetry: Performance of Animal-Tracking Systems

Abstract

We used 10 Telonics ST-3 platform transmitter terminals (PTT's) configured for wolves and ungulates to examine the performance of the Argos satellite telemetry system. Under near-optimal conditions, 68 percentile errors for location qualities (NQ) 1, 2, and 3 were 1,188 903, and 361 m, respectively. Errors (r E ) exceeded expected values for NQ=2 and 3, varied greatly among PTT's, increased as the difference (H E ) between the estimated and actual PTT elevations increased, and were correlated nonlinearly with maximum satellite pass height (P H ). We present a model of the relationships among r E , H E , and P H . Errors were bimodally distributed along the east-west axis and tended to occur away from the satellite when H E was positive. A southeasterly bias increased with H E , probably due to the particular distribution of satellite passes and effects of H E on r E . Under near-optimal conditions, ≥1 sensor message was received for up to 64% of available (P H ≥5°) satellite passes, and a location (NQ≥1) was calculated for up to 63% of such passes. Sampling frequencies of sensor and location data declined 13 and 70%, respectively, for PTT's in a valley bottom and 65 and 86%, respectively, for PTT's on animals that were in valley bottoms. Sampling frequencies were greater for ungulate than for wolf collars