This following glossary sheds light on how unique Albuquerque's new GPS system—the first government-owned system with tri-constellation capability—is.

GPS: The U.S. Global Positioning System. A system of 32 satellites built and maintained by the U.S., it was the first purpose-built navigational satellite system.
GPS is also the commonly used acronym for the ground-based instruments that use signals from the Global Navigation Satellite System (see "GNSS" below) for navigation and location.

GIS: Geographic information system. A GIS database combines information from many sources to produce a detailed, multilayer "picture" of a geographic area. Typical information includes location and elevation data from a GPS-based survey, aerial and ground-level photographs, infrastructure information such as street and building names, political boundaries, and virtually anything else that can be captured and stored electronically.

GNSS: Global Navigation Satellite System. A generic description of the two, soon to be three, constellations of navigation satellites orbiting the Earth. These are the U.S. GPS, the Russian Global Navigation Satellite System (see "GLONASS" below), and the upcoming European Galileo system. While each system operates independently and on separate frequencies, the best ground-based equipment is able to use signals from all three to provide comprehensive, 24/7 operation.

GLONASS: Global Navigation Satellite System. The Russian equivalent of the U.S. GPS, it has 16 satellites.

Galileo: The European equivalent of the U.S. GPS, scheduled to become operational in 2011-2013.

RTK: Real-time kinematics, also known as carrier-phase enhancement (CPGPS). A technology that permits millimeter-accuracy location between a base station and a rover that are in radio communication. RTK is particularly applicable to GNSS-based surveying. By comparing minute differences between the satellite signals received by the base station and the rover, an RTK system is able to provide real-time corrections for signal variations produced by atmospheric conditions, improving GNSS resolution to millimeter accuracy.

Base station: A GNSS receiver capable of highly accurate positioning (typically via RTK) and able to communicate with rovers via radio frequencies. A base station may be permanent or temporary, but is always positioned with extreme accuracy since it serves as the reference point for measurements made with the rover.

Rover: A portable GNSS receiver equipped for radio communication with a base station, and software to compare and resolve differences between the internal and base station GNSS signals.

Virtual reference station: A network of RTK-capable base stations that improves the accuracy and reliability of the measurements taken within the network area by supplying multiple RTK references to a rover.

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