Out in Front: June 20, 1996
The Ashtech GG24 Eurocard OEM board provides integrated access to satellites of the US Global Positioning System (GPS) and the Russian Global Navigation Satellite (GLONASS) system. The board receives, demodulates, and decodes satellite navigation signals from both 24-satellite systems. The combined system receiver gives users increased satellite visibility and, thus, signal availability approaching 100% compared to a single-system receiver. Because it requires readings from four satellites to establish position, a GPS-only system, for example, may have availability of 75% or less, depending on natural and manmade obstructions. In addition, those satellites that are visible may be in relatively similar alignments, which degrades the position-decode algorithm's accuracy.The GG24 includes both RF and baseband signal-processing circuitry and requires just a signal from an appropriate antenna. It has 12 parallel GPS channels and 12 parallel GLONASS channels, and it automatically selects the best available constellation for the most accurate position results. The circuitry includes algorithms for corrections to satellite information, including differential corrections. In addition, the receiver's autonomous integrity-monitoring algorithms detect and remove erroneous measurements. The 16.7×910-cm Eurocard with a DIN64 connector also has two RS-232C ports, and it consumes 1.8W from a 5V supply. It costs $5995 (one). A sensor package, which includes ruggedized aluminum housing, an internal PCMCIA memory card, and a power supply, costs $9995.
—by Bill Schweber
Ashtech Inc, Sunnyvale, CA. (408) 524-1400, http://www.ashtech.com..