Researchers from the University of Oxford have developed a low-cost, low-powered satellite tracking system to monitor endangered sea turtles. Their goal was to make the hardware simple and energy-efficient while offloading most of the signal acquisition and processing as possible. The team — Amanda Matthes and Jonas Beuchert, supervised by professor Alex Rogers — succeeded with the SnapperGPS, which employs snapshot GNSS for tracking and a web server hosted in the cloud for signal processing. What’s more, the barebones receiver costs only $30 to build and can run on a single coin cell battery for 10 years.
The advantage of using GNSS for the system is that it only requires a few milliseconds to acquire a satellite signal, a must-have as sea turtles spend most of their time underwater and only come up for air for a brief period. That said, the researchers encountered a problem with the initial design of the SnapperGPS, as the hardware could only record signals at lower resolutions compared to existing receivers.
To overcome the issue, the team developed and implemented three alternative algorithmic approaches to location estimation from short low-quality satellite signal snapshots, which are all based on probabilistic models. This made it easy for the Silicon Labs EFM32HG310F64 microcontroller to grab the snapshots and upload them to the cloud during the short intervals the sea turtles come up for air.
The researchers tested the SnapperGPS this past summer using waterproof (to 100-meters) enclosures and strapped them to 20 Loggerhead sea turtles on the island of Maio in Cape Verde. Due to COVDI, they tagged the animals late in the season, which happens to be the turtle’s nesting time and affected the recovery rate of the SnapperGPS tags. Out of those 20, only nine were recovered, but they did manage to show several location tracks and unexpected diverse behavior among the turtles.
While their efforts were not a complete success, the researchers gained valuable insight into Loggerhead populations around the island and are currently working on an improved SnapperGPS unit they hope to deploy before next year’s mating season.