The Global Positioning System (GPS) is a satellite-based navigation system comprised of a network of 24 satellites placed into orbit by the U.S. Department of Defense. On Earth, GPS receivers take this signal information from multiple satellites and use triangulation to calculate the user’s exact location. Cellular networks are being used to “fill in gaps” in transmission signals. In community corrections, where GPS offender tracking continues to grow, this is an important matter to consider.
Today, there are three different transmissions modes being used in community corrections to support the delivery of accurate, reliable signals to GPS tracking receivers and overcome geographical or atmospheric challenges. These modes include:
- Receiving signals via the GPS satellite network only (Autonomous GPS);
- A combination of GPS satellite data with support from a cellular network (Assisted GPS);
- A method that measures signals from nearby cellular towers and reports the time/distance readings back to the locating towers (Advanced Forward Link Trilateration) to determine an approximate location of the GPS receiver.