The Transmitter built into the device sends a signal to the satellites orbiting the earth. This signal allows the satellites to determine your position. The GPS unit is programmed with maps of specific areas and has roads programmed in. It can thus compute routes to different coordinates because it knows your location from satellite.This would be an active tracking system IE: EPIRB (an emergency locator beacon)
Passive systems are far more common IE: vehicle logging/tracking. These utilize a GPS receiver which receives signals from the current GPS satellite constellation and the internal processor computes your position. This position is then actively (transmitted) via any number of RF means (Cellular, VHF, UHF etc) to a receiving unit.
We are update pet gps tracker tk201-2 , and make it more small size and the case is waterpoof IP65 .
And stand by time is more longer than before , we call this model is tk201-3