Alternative GPS system is promising for simple applications
Many farmers see potential in the use of RTK-GPS, but they are turned off because of its high cost and uncertain returns. In early November, eFarmer, a Dutch start-up, came to the Inagro bio farm to present their alternative FieldBee system and to compare it with a commercial RTK-GPS system.
GPS uses satellites in combination with correction signals from reference stations. These reference stations can come from the FLEPOS network that is freely accessible to everyone (in Belgium) or from a dealer network. The precise position of these reference stations is known and they transmit a correction signal to the GPS receiver on the tractor or machine. When these RTK (Real Time Kinematic) corrections are used, accurate corrections can be made within 3 cm, and this accuracy can also be repeated over time.
This is important for making straight tracks, avoiding overlap between operations, working with fixed tracks and hoeing. Classic RTK-GPS systems consist of an antenna for reception of the satellite and correction signal, a gyroscope to correct the slope, a terminal, and an integrated hydraulic steering module. Depending on the version and the tractor, the total costs €15,000 to 20,000 for the entire system. Entry-level models for GPS control without RTK correction are much cheaper but are usually only accurate to 20cm. They are sufficient for spraying and spreading fertilizer, and can result in savings of up to 10% by avoiding overlap.
eFarmer has developed an RTK-GPS system with a highly simplified and more economical approach. The FieldBee (a satellite receiver) is installed on the roof of the tractor and wirelessly connects to an app on the smartphone or tablet of the user. The RTK correction signal is taken from the FLEPOS network. The cost of this system is an annual subscription fee of €118 for the application and a one-time purchase of the FieldBee GPS receiver priced at €648.
In addition, the user must have mobile internet on his smartphone or tablet to make the connection with FLEPOS (normal consumption estimated at 300 to 500 Mb per month). In comparison with classic entry-level models for GPS control, these costs are far lower. The FieldBee still does not have autopilot. It needs to be manually controlled in the direction the FieldBee app shows on the screen of the smartphone or tablet. It can, however, be upgraded to automatic steering.
The FieldBee antenna is simply placed on the roof of the tractor with a magnet. The software is user-friendly and easy to install on a tablet or smartphone. No additional wiring is required for installation. At the start of the test, the system needed a few minutes to achieve RTK precision. eFarmer indicates that the coverage of the FLEPOS antennas is not perfect everywhere. If the closest antenna is at some distance, it may take some time for the system to stabilize.
Once the system stabilized, an average accuracy of up to 5 cm could be maintained during the test without additional correction. The same paths were driven several times. We saw an average accuracy of 4 cm with a standard deviation of 2 cm and a maximum deviation of 10 cm. If necessary, an additional accuracy (0-4 cm) can be obtained by using a base station (cost €1100). This fixed station will amplify the correction signals and send them to the receiver on the tractor.
If necessary, an additional accuracy (0-4 cm) can be obtained by using a base station (cost €1198). This fixed station will amplify the correction signals and send them to the receiver on the tractor.
Possibilities and limits
The system is certainly suitable for rough GPS work (eg tillage, fertilizer spreading, splitting plots, etc.) and is a viable alternative to traditional entry models. Keep in mind that you always need to have your smartphone or tablet in the tractor. The system should also appeal to smaller companies that work on beds and are now ‘driving in rail’. Because inaccuracies do not accumulate, the system should maintain the beds sufficiently during preparatory fieldwork activities For the time being, the FieldBee is still insufficiently accurate for precision work (eg straight driving, hoeing, fixed tracks, etc.) but an extra base station could serve this purpose.
A disadvantage of the system is its lack of tilt compensation, which means that inaccuracies can occur on steeply sloping plots or at high speeds on rough terrain. It is also not yet possible to make a connection with automatic steering units on the tractor or machines, with section control or with machines that allow variable dosing. eFarmer plans to develop these applications in the future. In the short term, the traditional RTK-GPS systems for these applications remain a must.