Don, as I understand it, the Deere data loggers are smart enough to recognize GPS presence and use it when ground speed from the transmission pickup is greater than 1 mph.

The surface vs. horizontal plane area question is very interesting.    When you get a chemical recommendation for 1 pint per acre, and use a ground speed sensor for application, you could be dead-on with the recommended application rate.   But when you report summary info to EPA, you would have used more chemical than recommended based upon FSA/horizontal-plane area measurements for the field.    So, do you go for the recommendated rate for the field (what we call the business rate), or the recommended rate for the precise locations within the field (what we call the agronomy rate)?

The normal response to this question by gov't officials is that "there is enough tolerance in our rate checks to avoid an issue in either scenario."   So, they duck the issue.