New GPS Developments and Ashtech M-XII

Javad Ashjaee, Robert Lorenz, Robert Sutherland, Jean Dutilloy, Jean-Baptiste Minazio, Reza Abtahi, Jean-Marie Eichner, Joanna Kosmalska, Roger Helkey

Abstract: Several enhancements on GPS technology are presented. They encom­pass new data processing algorithms, enhanced application techniques, more hardware capabilities, and reduction in size and power consump­tion. Cost reduction is a natural consequence. Use of Doppler measurements for instantaneous (every one second) stationary position fixes is introduced. This technique has the potential of reducing the effect of "Selective Availability" in static point positioning. It is shown that the combination of Doppler and code phase (pseudo­range) measurements can provide two dimensional deterministic static position fixes (and time) with only two satellites. It also can provide three dimensional position fixes (and time) with three satellites. The proposed techniques expand the usage of GPS in areas with low satel­lite visibility (e.g. forests) and in the interim period while the GPS satellite constellation is not complete. Definition and physical interpretation of GDOP for the hybrid use of Doppler and code phase are presented. The notion of "Multiple Ramp" smoothing of code phase with in­tegrated Doppler is introduced. The result of implementation of this technique in Ashtech XII receivers for real-time differential GPS is given. Minimizing the errors in the use of GPS for aerial photogrammetry applications is discussed. A new technique implemented in Ashtech XII GPS receivers is presented. A new generation of GPS receiver (Ashtech M-XII) is introduced. It is capable of performing precision survey (static, kinematic, and pseudo­-kinematic), navigation, and time transfer. The new 12 channel receiver employs higher level of hardware integration. The heart of this 12-channel GPS receiver (including RF, GPS signal processing, and navigation processing) can be housed in a volume of about 50 cubic inches (7 x 6 x 1.2). Adding an 8-lines by 40-character alphanumeric/graphic display, an expanded range (9 to 32 volts) power supply, capacity for 48 hours of data recording, 30% spare volume for future expansions, and mounting each electronic board on a separate sheet of metal for durability, has increased the dimensions to 8.5 x 8 x 3.9 inches.
Published in: Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989)
September 27 - 29, 1989
The Broadmoor Hotel
Colorado Spring, CO
Pages: 195 - 198
Cite this article: Ashjaee, Javad, Lorenz, Robert, Sutherland, Robert, Dutilloy, Jean, Minazio, Jean-Baptiste, Abtahi, Reza, Eichner, Jean-Marie, Kosmalska, Joanna, Helkey, Roger, "New GPS Developments and Ashtech M-XII," Proceedings of the 2nd International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1989), Colorado Spring, CO, September 1989, pp. 195-198.
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