Whos barn is that out there across the field? Looks like I could easily see someone in the stand from the barn using my binoculars. MAy have to watch a few minutes but eventually you'd see them looking around the tree to check the field and edge.

Then, a simple call to the law and if they couldn't get there in a decent amount of time I would just set the vidcam to rolling and blast across that field in a truck or atv. He would be caught dead to rights. The law could use the tape to cite him.