![]() The tag stays on the animal, and the transmission doesn’t need another communications network. ![]() A local remote network downloads to a base station (e.g.You can also remotely (wirelessly) retrieve data from a GPS tag in several ways, listed by increasing coverage: Since it doesn’t require a transmitter, it is generally the cheapest GPS option. It doesn’t transmit information, so it needs minimal battery power and can be small. An “archival” tag collects and stores the positional and other data until you recover the tag from the animal. The GPS satellites continually transmit their positions, and the tag does the receiving. A previous Mongabay-Wildtech post on real-time wildlife monitoring offers a primer on GPS tracking. The more spread out the satellites, the more precisely the location can be estimated. It calculates the tagged animal’s location by triangulating the position of three or more of these satellites. So what is a GPS tracking tag, and how does it work?Ī GPS-based tag receives radio signals from several of the GPS satellites that continually orbit the Earth. It requires four or more transmissions to calculate the location, which may be more difficult in tropical locations far from the orbit. The processing center beams the information electronically to the researcher’s computer.ĪRGOS uses polar-orbiting satellites, so tags at high latitude locations typically have better coverage than those near the Equator. It calculates positions based on the change in frequency of an electromagnetic wave when the transmitter and receiver are in motion relative to each other, similar to how you hear a train going by. There, it estimates location using the change in the satellite’s position, its speed and distance from Earth, the frequency of signals, and the relative location of the tag in each signal. As the ARGOS satellite orbits, it picks up transmissions from a tag as it passes over the area and relays the positional and environmental information back to a data processing center on Earth. Image credit: Argos systemĪRGOS, launched in the 1970s, uses a Doppler system to determine positions. The researcher programs the tag to send particular information-such as the time, date, latitude, longitude, animal’s ID, and quality of the transmission (to estimate position accuracy)-to the satellite network, like a mini satellite telephone. How does ARGOS transmit to outer space and back?ĪRGOS-based satellite tracking is similar to VHF radio tracking, in that a small electronic tag fitted to an animal sends out an electromagnetic radio signal, except that in this case the signal is sent to a satellite in outer space instead of to a radio receiver one, five, or 10 kilometers away. The two systems work in slightly different ways: ARGOS-based tags send information to their respective satellites, while GPS-based tags receive position data from their respective satellite network.īoth systems send information on tagged animals’ locations directly to researchers, rather than the researcher having to manually locate the “ping” of a VHF radio transmitter in the field. Most satellite tracking of wildlife uses either the ARGOS (Advanced Research and Global Observation Satellite) or the Global Positioning System (GPS) satellite network. A GPS-tagged lioness leads her family in Hwange National Park, Zimbabwe. Improvements in communications technology, specifically transmission to and from satellites, have since revolutionized wildlife tracking. In the last Facts & FAQs post, we learned how researchers use radio transmitter to search for animals in the field and determine their locations. You can follow some animals around on foot or in a car, but you can’t follow a whale, a herd of migrating caribou, or a far-flying pigeon or parrot – they go too far, too fast, and in the wrong directions. To understand the resource needs of a species, you need to know where individual animals go and what they do there. Nevertheless, they provide automated collection of thousands of point locations of an animal, which helps researchers to more precisely define home ranges, migration routes, and the relationships of these patterns to landscape features. Satellite-based tags weigh more, cost more, and demand more power than VHF radio tags.GPS tags receive position information from multiple satellites and either store it or resend it via another communications network. ARGOS satellites use their relative position and the Doppler shift to estimate a tag’s location, which they relay back to Earth.Satellite-based tracking tags, including ARGOS and GPS systems, collect and communicate animal locations and in some cases, acceleration and physiological data-straight to your computer, 24/7.
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