GPS Applications in Wildlife Tracking
This newer technology has become entrenched in countless applications, including radio telemetry and tracking systems. A GPS receiver can be used to accurately track the location of an animal more accurately than ever before. Tracking products that utilize GPS technology are available for birds, marine mammals and terrestrial wildlife. Often, a GPS location is taken and stored on the tracking unit or, in some cases, transmitted to another source (i.e., satellite, radio receiver, cell tower).
GPS is a worldwide radio-navigation system formed from a constellation of twenty-four satellites and their ground stations. The system uses these satellites as reference points to calculate positions accurate to a matter of meters. The satellites are continuously transmitting information about their location and time. A GPS receiver operates by measuring its distance from each of the visible satellites. Line-of-site visibility is the key to getting an accurate location. The more satellites visible to the GPS receiver, the more accurate the location. A minimum of four visible satellites will enable a GPS receiver to get a location within 15 meters (or less) of an actual location.
After considerable engineering effort, ATS began manufacturing GPS collars in 2000. In fact, ATS was one of the first manufacturer’s to successfully develop and deploy a tracking collar utilizing GPS technology. The collar features a specially designed release mechanism which will allow it to drop-off of the animal. Two models are currently available from ATS. The G2000, which is for large mammals and ungulates, and for smaller terrestrial species, the G2110. Operationally, both are identical; the only difference is in the size and fit of the collar.
ATS' G2110 Small Mammal GPS Collar, and G2000 Large Mammal Collar
GPS Collar Functionality
ATS’ GPS collars offer essentially three different functionalities. The collar includes as standard a VHF beacon transmitter, allowing the researcher to track the animal with a receiver and antenna. Like the standard collar, the included mortality option will trigger a higher pulse rate than normal. When the on-board processor determines a GPS fix has been successfully recorded in memory, the VHF transmitter will emit a double pulse every sixth pulse. In addition, a GPS receiver is built-in to the collar. This allows the user to record, or log, the lat/long location coordinates of the animal on a user specified time interval. Also stored in memory are date and time tags, and other operational data coming from the GPS satellites. Thirdly, a collar release mechanism is incorporated into the collar, allowing the researcher to automatically trigger the collar to drop off. A specially designed powder-charged “squib” pops off the collar. It can be triggered remotely using a Command Unit available from ATS, (G2000 Model) or the unit may be programmed to drop-off at a user specified time (G2110 Model).
The unit is capable of recording ambient temperature, as well as activity and mortality data. ATS’ GPS collars are pre-programmed at the factory, based on the individual customer’s requirements. A GPS Programming Data Sheet is used to select programmable variables. Also, a Windows® based software package, ATS WinCollar, and an interface cable are shipped with each order, allowing user’s to download all of the data collected, and if necessary, re-program the collar’s processor.
GPS collars can currently sample on one or two different schedules. GPS location data may be programmed to be logged from once every 15 minutes, up to once every 255 days. It is our recommendation to sample on times that do not divide into 24 hours. Sampling, every five hours, for example, will vary the time of day that fixes are recorded, usually yielding better data sets. Total on-board non-volatile storage is 256K, which is approximately 8190 location stores. Keep in mind that there is a trade off between number of GPS locations logged and battery life. The GPS receiver consumes the most battery life, so if your research requires extended transmitter life, try to minimize the number of location “fixes” you record. Additionally, the researcher can monitor the collar using the VHF transmitter. A special low battery release feature will insure that the collar will automatically drop-off the animal should battery voltage reach a critically low level. In this case, the VHF beacon transmitter will continue to operate for at least thirty days.
For assistance in selecting and utilizing GPS tracking collars in your next project, contact the experienced wildlife biologists at ATS.
