Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2005
Publication Date: July 20, 2005
Citation: Peters, R.T., Evett, S.R. 2005. Mechanized irrigation system positioning using two inexpensive GPS receivers. In: American Society of Agricultural Engineers Annual International Meeting Technical Papers, July 17-20, 2005, Tampa, Florida. Paper Number 052068. 2005 CDROM. Interpretive Summary: From an airplane window, it is clear that center pivots are a very popular method of irrigation. Advances with center pivot irrigation allow varying amounts of water to be applied to different areas of the field based on soil or plant differences across the field. This requires more precise knowledge of the pivot's field position than is currently possible. A GPS receiver mounted on the end of a pivot can give this field position more accurately, thus enabling these advanced irrigation technologies that are developing. The use of a second GPS receiver in a stationary position to further correct the position estimates of the pivot-mounted receiver was tested. It was found that significant improvements were not possible with this method.
Technical Abstract: Precision irrigation or chemigation using mechanized irrigation systems such as center pivots or lateral moves requires accurate and real-time knowledge of the irrigation system's field location. A GPS receiver mounted on a center pivot or lateral move has the potential to increase the accuracy of these position estimates. Differentially corrected GPS receivers have become more affordable (less than $200 US) and it has become more feasible to use them for reporting field position of mechanized irrigation systems. Although these low-cost differentially corrected receivers have been shown to have accuracies of 95% less than 2.1 meters in previous experiments in the Panhandle of Texas, the remaining 5% of the reported points gave errors greater than 6 meters. These errors are large enough to present problems for site-specific irrigation. It was hypothesized that the errors from an additional GPS receiver in a known, stationary location could be used to correct the positioning estimates of the receiver mounted on a moving irrigation system and thereby improve the accuracy sufficiently for use with precision irrigation or chemigation. This was tested by placing two similar low-cost receivers in stationary locations and correlating the errors in the North-South and East-West directions. The r2 values of the linear regression lines were very small, showing that almost no correlation existed between the errors of these two receivers. This demonstrated that the integration of an additional, stationary low-cost GPS receiver will not significantly improve positioning estimates of GPS receivers mounted on moving irrigation systems.