Trimble Outdoors SPSX51 - Manual (Page 34)

4 Setup Guidelines
32 SPSx51 Modular GPS Receivers User Guide
Base station operation guidelines
A base station consists of a receiver that is placed at a known (and fixed) position. The
receiver tracks the same satellites that are being tracked by the rover receiver, at the
same time that the rover is tracking them. Errors in the GPS system are monitored at
the fixed (and known) base station, and a series of position corrections are computed.
The messages are sent through a radio link to the rover receiver, where they are used to
correct the real time positions of the rover.
Base station components
The base station has the following components:
• GPS receiver
• GPS antenna
• Base station radio
• Power supply
GPS receiver and GPS antenna
The base station GPS receiver can be one of following types:
• A Smart GPS antenna, such as the SPSx81, which incorporates a GPS receiver,
GPS antenna, power supply, and radio into a single compact unit. A Smart GPS
antenna can be rapidly set up on a tripod, fixed height tripod, or T-Bar anywhere
that is convenient on the jobsite.
• A Modular GPS receiver, such as the SPSx51, which incorporates a GPS receiver,
power supply, and radio in a single unit. The GPS antenna (and, optionally, the
base station radio antenna) is separate from the receiver. Because the GPS
antenna is separate, you can use the following optimized components:
– a geodetic antenna with large ground plane, to eliminate multipath (the
major source of GPS errors) at the base station
– a high-gain or directional radio antenna, to increase broadcast range and to
provide maximum coverage
You can also place a modular GPS receiver in an easily accessible and secure
location, safe from theft and the weather, while the antennas are placed high on
a tower or building, clear of obstructions and able to deliver maximum
performance.
You can use either type of receiver in a permanent, semi-permanent, or daily quick
setup configuration. If semi-permanent or permanent operation is required, however,
the modular receiver delivers significant advantages.