I just went through this last week with a cable company trespass. There are NO easements on my 25 acres, not even for the road. Your deed records it all. My county publishes not only the legal description of all properties but the surveyed latitude and longitude of each corner and neighboring lot markers. So, I'm surprised to find a fresh survey nail with a pink ribbon 100' south and 37' west of my well established corner monument (a 4" concrete cylinder). The marker has letters indicating a "hand hole" placement which usually means a fiber optic junction box.
Ain't gonna happen. I found out who the surveyers were by calling just about every one in town. Turns out it was just a reference marker used because of visibility needs. A careless choice of nails, too.
But, find out if your property line is actually what you think it is. I have used Google Earth to get measurements within a foot of what my legal description is. Make some measurements and check what you can.
When you have the property surveyed, ask that permanent concrete monuments be placed with brass I.D. labels on them. Take pictures of their locations because your 'friend' may actually attempt to move them (and succeed). Moving or removing a survey marker is a crime in my county. Not sure about the State. And surveyers have legal rights to access properties without notification.
Not sure what my next steps would be in your case, but make sure you have registered letters to the neighbor protesting his trespass. The courts will want and need to see this evidence.
BTW: In my first trespass court case (MediaOne Cable company) courts awarded $1000 per day for 'rent' of my poles as real damage with the cable company forbidden to come on to my property to remove their guy wire and cable. After MUCH deliberation, planning, safety studies, scrap yard value estimates, an organized neighborhood meeting a vacation and some dog training, I carefully and meticulously used my trusty shotgun to drop the wires. I was a VERY time consuming ordeal, but did not trouble my heart one bit to cash the check from the District Court.
You probably will wind up in court. My survey: $5500, my lawyer fees (She is know as a barracuda): $9000, value of the experience: Priceless ! Even raccoons are afraid to trespass now.