GPS field procedure

The field procedure of a GPS survey (static or kinematic relative positioning) is:

1. Reconnaissance and planning: study the project area, the existing control points and the sky visibility. Plan the network, receivers, observation sessions and baselines. Check the satellite availability and DOP (mission planning), and choose a time with good geometry (PDOP below about 6).
2. Selecting stations: points should have a clear view of the sky above about 15° elevation, and be away from reflecting surfaces (multipath), power lines and transmitters.
3. Setting up the receiver: the tripod and antenna are centred over the station mark with an optical plummet and levelled; the antenna height is measured (before and after observation) in two or three places, and the antenna is oriented to north if required.
4. Observation: switch on the receiver, set the recording interval (e.g. 15 s) and elevation mask, enter the point name and antenna height, and log data for the session length (static: 30 min to several hours depending on baseline length; RTK: a few seconds per point).
5. Record keeping: field sheets record the station name, receiver and antenna numbers, date, start and end times, antenna height and weather.
6. Data download and processing: the data are downloaded to a computer, baselines are processed, and loop closures and quality checks are done. The network is adjusted and the coordinates are transformed to the local datum.
7. Checking: some baselines are repeated as a check, and results are compared with known points.