A base station is a reference point for surveying activities that allows technicians to check in with a global positioning satellite (GPS) transceiver at a known geographic location. In addition to being used in surveying, base stations are also useful for other activities where people may use GPS devices for positioning. Base stations allow for error correction and increased precision, both of which may be critical for some tasks. Devices may communicate automatically with a base station, or the user may need to subscribe to a service to access the signal.
Government agencies install base stations at key locations, and they can also be put in place by private companies. The base station communicates with satellites and takes note of any errors. When rovers communicate with the base station, they receive data about errors and use it to correct their own readings for accuracy. Maintenance of the base station ensures that it remains as accurate and usable as possible.
Placement of base stations requires some care and thinking. Signal strength is a key consideration, especially in an area where coverage may be limited and the station needs to reach across a large portion of the landscape. Signal clarity is also important. If the signal drops out, it could create problems, and might potentially be dangerous; hikers, for example, need continuous signal coverage to ensure they stay on track and are familiar with their location.
Two separate issues must be considered with base station placement. The first is visibility. The station should be on elevated ground, with a clear line of view around the surrounding region. If it is in a recessed area or a location with numerous hills, rock outcrops, and other obstacles, the signal will not be as strong and the coverage area may be limited. Surveyors can consult maps and other data to determine a good site, and may also consider weather conditions in their decision, as these can have an impact on location selection.
The second issue is the potential for interference from other sources. A base station near electrical lines, radio relays, and other sources of electrical interference will not work as well. Remote locations tend to work best because they do not contain as much interference, although the crew may also need to think about access issues. If a base station is too remote, it may be hard to reach, especially in inclement weather, and this could pose an obstacle to routine servicing and maintenance.