Planting Barley with GPS

I have an update to my barley field. Have been off planting a few miles away. Our barley field is on riverbottom and can easily be seen from the road. Of course this is where we always have planting screw ups.
We had disked this field first so it was very hard to see what had been planted. Not to worry, I have GPS! Not the straightest rows I've ever made. Plus there are a few skips...
Note the darker strip down the middle with a two-foot skip beside it. That is my return pass which was supposed to be back down the middle, right over the top of the skip! For some reason my GPS was way off that week. Probably was George Bush's fault. This week it has been right on. Now I don't trust it anymore! Guess, I won't sell my foam marker.