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The GG Surveyor™ is the first all-in-view GPS+GLONASS™ receiver. It's revolutionary
design allows smooth integration into a wide range of positioning applications on land, sea
or in the air.
One of the primary advantages of GPS+GLONASS is increased satellite coverage. With a
total of 40 healthy satellites, there are 60% more satellites available for position
computation than GPS alone. Thus, GPS+GLONASS is extremely beneficial in
obstructed operating environments, such as in cities, mountainous areas, under tree cover,
or other areas where much of the sky and many of the satellites can be blocked.
To take advantage of the increased satellite availability, the GG Surveyor has 12 channels
for L1 GPS and 12 Channels for L1 GLONASS, providing all-in-view tracking for both
constellations. Autonomous GPS+GLONASS positions typically have 16 meter
accuracies compared with 100 meters for GPS alone.
Differential corrections and RTK messages are available for both GPS and GLONASS
providing real-time, on-the-fly centimeter accuracy when the GG Surveyor is used with a
base station and data link.
Functional Description
The GPS constellation contains 26 usable satellites. As of December 1997, the GLONASS
constellation has 13 usable satellites of the planned 24 satellites full constellation. The GG
Surveyor provides the capability to track up to 24 GPS and GLONASS satellites
simultaneously. As the GG Surveyor locks onto the signal generated by each satellite,
information (ephemeris data) about the position of each satellite is automatically
downloaded and stored in receiver memory. Once the ephemeris data is collected, the GG
surveyor can compute its own position.
The GG Surveyor calculates three-dimensional position and velocity when tracking any
combination of five satellites (e.g. 3 GPS and 2 GLONASS). By holding the GPS-
GLONASS clock offset fixed, the GG Surveyor calculates a 3D position with any
combination of 4 satellites (e.g., 2 GPS and 2 GLONASS). By also holding the altitude
fixed, the GG Surveyor calculates a 2D position with any combination of 3 satellites.
Up to 5 independent measurements are determined per second, with no interpolation or
extrapolation from previous solutions. The position and velocity computations are
performed using all the satellites in view simultaneously (up to 16 when in 5 Hz mode).
The GG Surveyor uses a Doppler measurement technique for computing on-the-fly
velocity (no dependence on the previous position). All computations are accomplished
Introduction
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