Validation of a GNSS receiver for monitoring agricultural areas
The Rhineland-Palatinate Ministry of Agriculture used the i3mainz to validate several GPS receivers that are used to determine the cultivated areas. The aim of the validation is to determine a value that describes the accuracy of the GNSS receiver in combination with the measurement method used when determining the area.
Different systems for determining and allocating agricultural areas are used in the individual member states for the EU area payments and single farm payments. In Germany, ortho-photos from satellite images are mainly used, as they also recognize different types of cultivation, but also GPS. The Rhineland-Palatinate Ministry of Agriculture used the i3mainz to validate several GPS receivers that are used to determine the cultivated areas. In order to avoid misuse, the European Commission sets strict standards for the accuracy of the devices used. These must have been validated in a procedure that corresponds to the ISO 5725-2 standard. The JRC (Joint Research Centre), as the scientific arm of the EC, has developed a test procedure for this that must be strictly adhered to. This consists of several test measurements and their statistical evaluation to determine the accuracy of the measurement method.
First, a schedule for the test measurements was created in accordance with the specifications of the EC. The measurements on the test fields were then carried out by employees of the Service Center for Rural Areas (DLR) Mosel - Trier. The data obtained was then subjected to a detailed statistical analysis by i3mainz. The i3mainz worked closely with the JRC in Italy. The aim of the validation is to determine a value that describes the accuracy of the GNSS receiver in combination with the measurement method used when determining the area. For this purpose, five differently sized cultivated areas were circumnavigated four times in nine measurement series each by three different observers and the field size was determined. These 180 measured values were statistically examined for the comparison precision according to the ISO 5725 standard. First, outlier tests were performed, followed by analyzes of variance to check the significance of the influences of various factors such as direction of travel, observer, size and shape of the field on the result. Systematic errors must also be ruled out. The buffer sought as a comparison limit is then calculated from the variances of the measurement series.
Every GNSS device that is used in the European Union to determine the areas under cultivation must have been validated by a recognized laboratory. The i3mainz maintains a constructive exchange with the JRC about the use of GNSS devices, implementation of validations and the possibility of having the i3mainz certified as an accredited laboratory.