Enhancement of Global Positioning System with Dead Reckoning

J. van Bergeijk, D. Goense, K.J. Keesman

The design, test and results of a positioning system consisting of a Differential Global Positioning System (DGPS) receiver, a radar velocity sensor, a wheel velocity sensor and an electronic compass were discussed. Firstly, the characteristics of the individual sensors were investigated. With these results a Kalman filter design was made to integrate the different signals into a single estimate of position, velocity and heading. Field tests were conducted to investigate both the real time performance of the system and the robustness against distortions like malfunctioning of sensors. A nine state extended Kalman filter improved accuracy of positioning and was able to bridge gaps in position information due to GPS receiver blockage.

Presented at International Conference on Agricultural Engineering, Madrid, ES, 23-26 September 1996
Presentation Paper 96G-013, Abstract Volume 2, P 995-996
Submitted to and accepted by Journal of Agricultural Engineering Research, januari 1998

Soil tillage resistance as tool to map soil type differences

J. van Bergeijk, D. Goense

Precision agriculture incorporates spatial knowledge of soil and crop conditions in the management decisions. In this paper a method to improve determination of soil physical properties was proposed. Current practise is to analyse soil samples taken at several locations in a field. To obtain a sound coverage many soil samples have to be analysed. To reduce these costs, information gathered automatically during the major soil tillage operation was used. Measurements of plough draft proved to be useful to define different regions in a field.

Presented at The Third International Conference on Precision Agriculture, Minnesota, USA, 23-26 June 1996
Published in conference proceedings, P 605-616

Dynamic weighing for accurate fertilizer application

J. VAN BERGEIJK, D. GOENSE, L.G. VAN WILLIGENBURG, L. SPEELMAN

The mass flow of fertilizer spreaders must be calibrated for different types of fertilizer. To obtain accurate fertilizer application, manual calibration of actual mass flow to the theoretical mass flow has to be repeated frequently. An automatic calibration is possible by estimation of the actual mass flow based on dynamic weighing of the spreader. In this research, a dynamic weighing system is designed and tested. This resulted in weight readings under field conditions that had a standard deviation of 20 N, over a measurement range of 6 kN to 20 kN, with a time delay through filtering of a maximum of 1 second. Time stamped data logging of spreader weight, theoretical application rate and position information, gives the opportunity to relate the realized spatial application of fertilizer to the prescribed application rate.

Presented at The First European Conference on Precision Agriculture, Warwick, UK, 7-10 September 1997
Published in conference proceedings, Volume 1, P 263-272

Analysis, Design and Implementation of an Information System for Spatially Variable Field Management

J. VAN BERGEIJK, D. GOENSE, L. SPEELMAN

A characteristic of precision agriculture research is the cooperation between different research disciplines. Especially when research is carried out 'on farm' or at farm scale level, the data, collected by various measurement methods, has to be available to the respective disciplines working on their common goal of agricultural production optimization.

Based on an information model described by Goense et al, 1996, a database structure was implemented to support on farm research. Part of the database incorporates storage of farm management actions with their respective spatial measurements linked to geographical primitives like locations and areas. Functionality is extended to allow storage of future measurement methods in a standardized way and to use crop growth simulation models for optimization of prescription rates.

The implementation in a relational database management system offers the opportunity to use commercial GIS software as a graphical front end to the database. Connection to specific tasks like data exchange with field equipment and a link to crop growth simulation models is implemented through the use of a structured query language (SQL) interface.

Currently, the database is used by participating researchers from the soil science, agronomy, economics and agricultural engineering disciplines in a project with the objective to operationalize crop growth simulation models for field management.

To be presented at The Fourth International Conference on Precision Agriculture, Minnesota, USA, July 1998
To be published in conference proceedings