Comparison of a d-GPS system and conventional guidance for spraying applications

Abstract

A recent project undertaken by the University of Southern Queensland in association with Trimble Navigation Australia assessed and compared the accuracy of a DGPS based guidance system with a conventional guidance system for the application of agri-chemicals. The system being tested comprised a Trimble AgGPS 132 configured to allow drivers to follow a light bar of LED’s to enable them to accurately follow a series of parallel tracks. A series of tests were carried out at seven different sites using a variety of experienced and inexperienced operators. Data was collected in order to compare the GPS guidance against the conventional system of foam marking. Processing of the data required the generation of parallel swaths that replicated the coverage of the spraying rig. This was achieved through a process of buffering of the data in the geographic information system (GIS), ArcView. By generating these polygons for each successive run, the areas of missed spray (skip), and double spray (overlap) could be identified. Through a process of GIS overlays the resulting areas could be readily identified. The results of the project indicate that the particular GPS guidance system was of comparable accuracy to the conventional guidance by foam marking under ideal conditions. The results also indicated that GPS guidance is superior to conventional guidance where conditions for foam marking, eg wind and crop height are not optimal. The study found that both GPS and conventional guidance operators had a tendency to overspray their runs to ensure that they did not miss any areas.