Support
RTK/GNSS glossary
Glossary of RTK and GNSS terms: AB line, age of corrections, baseline, caster, GGA, mountpoint, MSM, PDOP, RTCM, VRS and other terms seen in terminals.
4 min read
| AB line | Reference driving line in agricultural guidance, defined by points A and B. |
|---|---|
| Age of corrections | Age of the last received correction in seconds. Ideally < 2–5 s. |
| Ambiguity | Unknown integer number of carrier wavelengths; once resolved – FIX. |
| Baseline | Distance between the rover and the base station. |
| Caster | Server that distributes corrections (NTRIP). |
| CTF | Controlled Traffic Farming – machines always drive in the same tracks. |
| GGA | NMEA sentence with position and solution status that the receiver sends to the caster. |
| ISOBUS | Standard (ISO 11783) for communication between tractors and implements. |
| Mountpoint | Name of a correction stream on the caster (we recommend AUTO). |
| MSM | Multiple Signal Messages – modern RTCM 3 messages for multiple constellations and frequencies. |
| Multipath | Error caused by signals reflected off surfaces before reaching the antenna. |
| PDOP | Measure of satellite geometry; lower is better (ideally < 2). |
| RTCM | Correction format standard (Radio Technical Commission for Maritime Services). |
| Section control | Automatic switching of sprayer/seeder sections on and off based on position. |
| VRA / VRT | Variable-rate application according to a prescription map (fertiliser, seed, crop protection). |
| VRS | Virtual Reference Station – a network RTK solution. |
Related: These terms are explained in context in what is RTK, NTRIP and RTCM and tractor auto-steer – for AB lines, CTF and section control, see also RTK in agriculture.