The data came from an Ag Leader. It is set at a two second log interval so I think he was probably running fairly fast through the field.

I agree that the map looks noisy but I think it's more the field than anything. This field is flat as a pancake and it was ridged terribly by the tillage practices of the previous owner. This causes small ponded areas throughout the field. These areas do not drain because there is no tile in the field. This is why you see some significant changes within a short distance.

As I indicated before, it has been my experience that when yield differences are below approximately 12 bu., it's very hard to display that difference on a map. It looks like to me that I need to play around with Terry's method's to see if I can extract such a small signal. If nothing else, his method of cleaning the data should help in making a much cleaner map to begin with. Now I just need to find the time to sit down and try to figure out how to do what he suggests in his paper.