What does “accuracy” mean in agriculture
Absolute accuracy means that if you specify your location, you will be able to return to this point in a day, month, year, with the level of precision that is listed in the technical characteristics of the receiver, for example – 4cm – 50cm – 1m. This is why absolute accuracy characteristics explain the applicability of a GPS receiver for surveying work.
Relative or pass-2-pass accuracy – shows how position deviates from a specific location if one comes back to it in minutes/days/months/years. This is what we need in farming when precision is important during the whole day/year and allows you to make parallel rows in the area.
If you want to learn more on different precision that you can achieve with different GPS devices and their practical implications, go here.
This article is going deep for those who want to understand better how the RTK system works and how to use it in a most convenient way for different cases and operations.
We would like to remind you that RTK system consists of GNSS receiver – rover antenna that goes on the tractors’ roof and Base station (BS) that transmits correction.
RTK BS can work in 3 modes:
- Fixed position;
- Absolute position.
How farmer sees navigation lines
It is when the position of the BS is not fixed and not defined.
In this regime every time after BS restart the farmer get RTK with centimeter accuracy but every time navigation lines will be shifted relative to the base station. And even if the BS did not change its locaton, the rows still be shifted after restart. That means that in some cases farmers might even need to create a new AB line to continue field operations.
Restart of the BS can happen when it is turned off, discharged or had to be restarted. Important also that shifting of position occurs only after restarting of BS not receiver (antenna that goes on the tractor roof). So if you turn off and turn on the FieldBee rover the navigation branch will remain the same.
Nevertheless this regime is useful in many cases. This regime is recommended for getting started with RTK system – for initial set up and testing to find the best location and for survey works. FieldBee customers receive base stations presetted in this regime.
Also this regime is recommended when a farmer carries the RTK system with him and often changes its location. This might be needed in cases when fields are located more than 20 km from BS, when there is no good WiFi and the system is used via radio signal. As well this can be done to perform contract jobs. If you are going to use the system at your neighbor location, don’t forget to restart the base, otherwise it will be using your previous location and navigation lines will not be relevant.
FieldBee Navigation app allows farmers to return to the same rows even when they are shifted, using Adjust location functionality. See how it works bellow.
It means that for a base station were applied defined coordinates with a range up to 5 meters but absolute position (very accurate) is not known. With such settings you can have repeatable precision year by year, so you will be able to return to the same navigation lines but all of this will be shifted according to your real field location.
Fixed mode, example of navigation lines behavior
It is when it is possible to define the exact position of the base station. In cases when NTRIP providers or cadastral services are available. For example, a farmer can have a mark on a field (usually metalmark) with a cadastral number. In this case, if to put station in this location and insert coordinates in the FieldBee ToolBox app the base station start working in absolute mode. Boundaries of fields, navigation lines, even between different GPS systems will be synchronized, will be the same every time a rancher goes to the area. That’s what absolute accuracy means – repeatable complete precision even between systems, continents, years and so on.
It is applicable for surveying fields for cadastral tasks, to locate and avoid obstacles in the field. And also when a farmer wants to continue operation after seeding. When the range is not visible yet when crops are not seen yet in this case absolute position accuracy is needed. Also for inter row operations and to go to the same lines year per year.