Welcome to Pond Boss.

I'm unable to see the picture, but be aware we're having some forum issues with posting pictures right now.

I'm not an attorney, but I would think that the starting points would be having a real survey done as well as appropriate title searches.

How was the land purchase handled?

Also, your state may have some specific laws about property lines.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."