The Use of Low-Cost, Differentially-Corrected GPS for Reporting Field Position of Self-Propelled Irrigation Systems

摘要

Precision irrigation and chemigation using center pivots and lateral move systems requires precise knowledge of the field position of the moving irrigation system. This kind of precision is not possible with typical methods of reporting angular position of center pivots. Lateral move systems do not have a readily-available, low-cost method of reporting field position. The decreasing costs and increased precision of differentially corrected GPS receivers make them a possible solution to this problem.Low-cost GPS units were ested at stationary positions in Bushland Texas and in Fort Collins, Colorado. Tests on a moving center pivot were performed in Fort Collins. Outlying errors from the reported GPS positions can be mitigated by averaging the GPS positions. Two different averaging methods were evaluated and an algorithm for combining these averaging methods with dead reckoning for reporting real-time position using recent historical data is presented. Various time periods for averaging GPS points were evaluated. Averaging time periods from 10 to 30 minutes bring in the outlying errors sufficiently without having to apply dead reckoning across long times and distances. There was good agreement on the moving pivot between GPS calculated angular datawhen compared with measured reference points. The position estimates improved by averaging over greater time periods. Averaging GPS points to calculate angular velocity decreases the variability of velocity estimates. Averaging times of 5 to 10 minutesappeared adequate to give good estimates of angular velocity.