Each of our devices transmits through one of two systems: the Argos system or the GSM system. Both have their advantages, and we recommend considering your study's objectives when deciding between the two.
|Solar Argos/GPS 30g PTT (left) and GPS/GSM 20-70 30g Transmitter (right) with shorter 3.35 inch antenna.|
Our Argos-certified devices are called PTTs (Platform Transmitter Terminals) and offer global coverage. All PTTs send data through the Argos constellation of polar-orbiting satellite modules and provide locations estimated by Argos based on the Doppler shift of the PTT's signal frequency.
Solar Argos/GPS PTTs and the Battery Powered Argos/GPS 105g LC4™ PTT not only yield Doppler locations, but are also equipped with an onboard GPS receiver. The high-resolution GPS location data these PTTs obtain are also transmitted through Argos.
Argos/GPS PTTs are programmed to acquire GPS fixes at user-specified hours, and transmit at user-specified intervals (typically about every 3 days). Despite limitations in data throughput that accompany satellite communication, these GPS-equipped PTTs are the ideal instrument for studies attempting to understand instances of mortality. They are not subject to coverage limitations and can be equipped with our Ground Track (GT™) technology. With Mortality GT™, a transmitter will emit a UHF signal upon registering animal inactivity for a prespecified period of time, allowing researchers to pinpoint detached PTTs or dead/injured birds. Experience has shown that locating "downed" PTTs can lead to critically important information about causes of mortality and population declines. PTTs can also be programmed with Seasonal GT™ that initiates the UHF signal during preprogrammed time periods. This enables localized detection of devices during certain times of the study cycle and aids in behavioral observation.
GPS/GSM 20-70 Transmitters are distinguishable by their 3.35 inch antennas, less than half the length of the antennas of our PTTs. GSM transmitters offer the potential for greater amounts of data due to their ability to record and transmit high-frequency GPS data, making them excellent for studying fine-scale habitat use. GPS fixes are acquired at intervals correlating to the battery voltage, such that GSM transmitters can acquire GPS fixes up to once a minute (current software version) when in good lighting conditions. The data collected includes high-resolution GPS locations as well as their corresponding error (VDOP and HDOP) data. As long as a transmitter is within range of the mobile network and can make a connection, it will send data daily. GSM transmitters archive data, so if a connection cannot be made, the unsent data are not lost. Instead, the data will be transmitted once the device is able to connect to the network again. However, if a bird dies or remains outside of cellular range, transmissions will not be possible. In the event that a transmitter is recovered, MTI can retrieve the archived dataset.