UAV wildlife radiotelemetry: System and methods of localization

The majority of bird and bat species are incapable of carrying tags that transmit their position to satellites. Given fundamental power requirements for such communication, burdened mass guidelines and battery technology, this constraint necessitates the continued use of very high frequency (VHF) radio beacons. As such, efforts should be made to mitigate their primary deficiencies: detection range, localization time and localization accuracy. The integration of a radiotelemetry system with an unmanned aerial vehicle (UAV) could significantly improve the capacity for data collection from VHF tags. We present a UAV-integrated radiotelemetry system that relies on open source hardware and software. Localization methods, including signal processing, bearing estimation based on principal component analysis, localization techniques and test results, are discussed. Using a low-power beacon applicable for bats and small birds, testing showed that the improved vantage of the UAV-radiotelemetry system (UAV-RT) provided significantly higher received signal power compared to the low-level flights (maximum range beyond 1.4 km). Flight testing of localization methods showed median bearing errors between 2.3° and 6.8°, with localization errors of between 5% and 14% of the distance to the tag. In a direct comparison to an experienced radiotelemetry user, the UAV-RT system provided bearing and localization estimates with 53% less error. This paper introduces the core functionality and use methods of the UAV-RT system, while presenting baseline localization performance metrics. An associated website hosts plans for assembly and software installation. The methods of UAV-RT use for tag detection will be further developed in future works. For both the detection and localization problems, the mobility of a flying asset drastically reduces tracker time requirements. A 7-min flight would be sufficient to collect five equally spaced bearing estimates over a 1-km transect. The use of a software-defined radio on the UAV-RT system will allow for the simultaneous detection and localization of multiple tags.