Long-term Tracking in Batmon: Lessons and Open Challenges

Abstract

Long-term tracking with battery-powered devices remains an unsolved challenge, mainly due to the high energy consumption of GPS modules. This talk will focus on our work, toward solving this challenge in the Batmon project, which conducts continental-scale long-term tracking of flying foxes as part of the National Flying Fox Monitoring Program in Australia. The monitoring program is targeted at understanding the Hendra disease spread risk and at assessing the ecological state of the species. At the core of our work is the multimodal GPS-enabled Camazotz sensor node platform that has been designed at CSIRO for flying fox collars, with a cumulative weight just under 20g. Recent research into long-term tracking has used low power sensors to detect events of interest in order to only obtain GPS samples when these events occur. The use of inertial sensors and short-range radio can reduce reliance on GPS to prolong the operational lifetime of tracking devices, but they only provide coarse-grained control over GPS activity. The inclusion of energy harvesting, such as solar panels, on the tracking devices themselves provides regular energy input that can be used for higher resolution sampling. With this capability, however, the available energy budget is dynamic and requires adaptive scheduling of GPS samples. Mobility is another independent and dynamic process that must be considered for long-term tracking. The mobility dynamics of the tracked objects (in our case flying foxes) determine how often interesting events occur, and therefore directly impact the frequency of GPS sampling. It is therefore necessary for effective tracking algorithms to use context-sensitive mobility models to guide scheduling and sampling decisions in localisation algorithms. The talk will discuss how we have addressed these challenges within the Batmon project. The project has already deployed tens of devices on live flying foxes, which have been operating in the field for several months. We are using the data from these devices to build mobility models and algorithms for designing the next generation of software, as we will progressively deploy up to 1000 nodes within the coming months. The progressive deployment of nodes coupled with delay tolerance, constrained resources, and incremental feature development raises interesting systems challenges and opportunities, which I will highlight in the talk.