When a salesman tells you that you can expect near perfect accuracy and repeatability if you invest in RTK differential correction, one of the most accurate choices available, you can believe them. The proof is in a graphic illustration of a soybean plot on the Meigs Research Center near Romney. It is part of the Purdue University farms system.
Pete Illingsworth, a seasoned veteran on the crew who also works at the Throckmorton Research Center, says the farm has its own RTK repeating unit on top of a grain bin near the Throckmorton buildings. At one point they had a problem because their GPS was picking up another signal from someone else's tower, and would veer off course. That's since been corrected.
He laid out the A-B lines around the plot. Once laid out, the GPS-computer interface knows where to place each pass in the field. He made one borer pass on the south end of the field before returning to the north end to start the actual planting of the trial.
When the tractor got to the south end, there would be either too much or too little space for a full pass. But when it reached the spot for the last pass, the perfect amount of space was left. Because he had trouble earlier in the year, he used markers just in case.
The maker on the next-to-last pass lined up perfectly in the groove cut by the marker from the opening border pass an hour earlier on the south end. The spacing was perfect.
"It's so good if you had corn and came in to sidedress, you could start on the opposite side from where you planted, and wouldn't have a problem," he notes.