[Trichl] creates a tiny GPS logger, called ‘TickTag’, that was designed as an inexpensive location tracking option for animal studies. The low cost, tiny form factor, and large power density of the LiPo battery give the TickTag the ability to track large populations of small animals, including dogs and bats.
The TickTag was designed with a LiPo battery specifically in mind and claims 10,000 GPS fixes from a 30mAh cell. Each unit is equipped with an L70B-M39 GPS module controlled by an Atmel ATTiny1626 microcontroller and sports a tiny AXE610124 10-pin connection header for programming and communication. GPS data is stored on a 128kB EEPROM chip with each GPS location fix using 25 bits for latitude, 26 bits for longitude, and 29 bits for a timestamp. All it all up and you get 10 bytes per GPS data point (25+26+29=80), giving the 10k GPS fix upper bound.
To record higher quality data and extend battery life, the TickTag can be programmed to record GPS location data using variable frequency intervals or when geofencing bounds have been crossed.
Since the device is so small, any errant signals close to the antenna can cause problems with receiving. [Trichl] warns that mounting the device should be well away from any other tags or conducting material, including its own battery, which is required to be mounted behind the tag, not under, to avoid drowning out the GPS signal.
Getting data off of the TickTag requires physical access to the device which can be done via
a companion “user interface board”. The interface board integrates charging logic and USB communication, among other functionality, reducing complexity in the TickTag module itself.
All source code, gerber files, design files, and 3d printed cases are available on GitHub. Besides the documentation and source code, their paper in the Public Library of Science (PLOS ONE) journal is full of details, including the results of embedding a device on a canis lupus familiaris.
Who knows, maybe the TickTag is even resilient enough to be used to track the catus domesticus.