If you have a fresh survey done, and it shows you to be in the 'right,' the neighbor either accepts it, or has his own survey done to contradict yours.
From the picture, it looks like a close call, so I'd want this laid to rest sooner than later.
Around here, if two surveys do not agree, the county surveyor has the final word as to who is right. After that, it would have to be litigated if not accepted, and that could cost more than the land is worth.
