Performance of a Decimeter Accuracy GPS Receiver for the Development of Topographic Maps

Producers have pointed to the investment cost of equipment as being the major obstacle of adopting precision agriculture. One piece of equipment important to precision agriculture is GPS (Global Positioning System). One use of GPS that has become prevalent is GPS auto guidance. GPS auto guidance has allowed producers to apply fertilizer and pesticides more efficiently and accurately with the elimination of skips and overlaps of the application equipment. With the availability of different levels of accuracy for GPS auto guidance, producers have questioned whether or not a sub-inch accurate RTK system is needed for the extra investment cost above a decimeter rated GPS system. If a decimeter rated GPS receiver is sufficient for GPS auto guidance then can the positional data collected be used to develop topographic maps. During the fall of 2005, a study was set forth to answer this question. For the study, a John Deere Starfire GPS receiver with SF2 differential correction and a Trimble AgGPS 252 with Omnistar XP differential correction were compared to an Ashtech ZSurveyor RTK GPS receiver. Preliminary tests were conducted by traversing parallel swaths 6.1 meters apart. Raw GPS data was collected from each GPS receiver to compare elevations. A preliminary test was conducted on an 8.1 hectare area. Elevation maps were developed from each GPS receiver and compared using linear regression analysis with an Rsquared value ranging from 0.68 to 0.99.