Our experience is w/the Trimble products & now Headsight.

We tried to make JD combine run in corn using RTK, following planter files. This was Trimble equipment in JD combine & JD planter. Neighbors have 100% JD equipment, but same problems.

75% of the time, combining corn will do OK w/autopilot. But, occasionally the corn head will wander 1-2" off either side of the row center. That's enough to start "pitching" ears or showing more shelling. Might be an individual thing. Perhaps some guys are happy w/2" variance in combine rows. We weren't. We tried for 3 yrs....some parts of field OK, some not. It was OK to eat a sandwich, or drink pop, or read o.m. on-the-roll, but not the perfection you dreamed of.

Our non-metric analyzation of the problem was one of distance. When we're planting w/RTK guidance, the tractor is guided dead-on. No problem. However the seed placement point is 15-20' behind the gps antenna. Nothing is logging the seed placement. Then when you combine, row entry is 10-12' ahead of the gps antenna. Again, there's plenty of room for movement error. So, you lose an inch w/planter (???) and another inch w/corn head(??). Now you have 2" s-turns thru the field. That was our experience anyway. Apparently viewing the industry trends, others experienced it also but may have been more quiet about it.

In the fall of 2008 we added the Headsight row guidance on corn head. It worked well for us & it could care less if we planted w/gps or not. Here's link to Headsight product.

http://www.headsight.com/images/truesight/truesight_logo.jpg