1. GPS satellite
The GPS system is based on a minimum of 24 satellites that circle the globe at an altitude of 20,000 kilometres. The system utilise several
satellites at any one time.
2. Signal
A normal GPS signal allows positioning within a few tens of metres. Since farmers need more precise
data, the signal from GPS satellites is corrected by a signal from either a geostationary satellite or local base station. This is referred to as differential GPS, or DGPS.
3. Tractor
The driver of the tractor can focus on his work instead of on steering. Sensors in the Auto-Guide’s TopDock automatically compensate for potential errors when the tractor is leaning, for example.
4. Driving lines
Valtra’s Auto-Guide system allows three types of automated steering: parallel (straight lines), contour (curved lines) and pivot (circular lines). The driving lines can also be stored in the system’s memory for precise repetition, even in the next harvesting season. Driving lines can also be transferred from one Auto-Guide system to another.
5. Satellite-based differential correction signals. The Auto-Guide system uses correction signals transmitted by geostationary satellites that remain at a fixed location above the equator.
6. Local base station
Enhanced precision for GPS navigation is possible by using a local base station. Local base stations offer precision of a couple of centimetres within a range of few kilometres, depending on the terrain. Local base stations require a bigger initial investment but are then cheaper to use than commercial correction signals.
7. Risks
The GPS system has been in use for decades and is essentially reliable. However, the system is sensitive to interference caused by different types of terrain, weather and the strength of the signal. The system may not work, for example, alongside large buildings or on small fields encircled by forest.
