OK, maybe someone here can figure this out for me.

This is for the woods at the farm......just FYI.

The woods is 80 acres, and lies as two forty acre areas back to back.....it's 80 deep, and 40 wide. The land boundaries are pretty much exactly N, S, E, and W lines.

I have the GPS coordinates of the NW corner. That is easily accessible, and is at the gate to the property off of a county road. The other end of that 40, the SW corner of the plot.......is also on the road and I have that GPS coordinate.

I have the SE GPS coordinate because got a guy to take me onto a fellow's property and we asked permission to drive down his side of the South line........because he's cleared his side out and it's down a 'road' accessible by wheely.

So, now I have 3 of the 4 GPS coordinates of a 80 acre rectangle. I have never been, to my knowledge, at the NE corner. It is possible it's in the middle of a slough.........

One additional piece of info...... I also have the midpoint of the north line marked. In fact, I have the north line marked with flagging tape to the end of the first 40........ Going past that point may require napalm, a D9 Cat, and a respirator. Not sure. But when I stand at that point, halfway down that line, it is approx 440 yards to the NW corner (gate), and 6XX yards to BOTH the SE and SW corners. That tells me I'm about halfway down that line.

(When I walked it last week, it took forever.......grown up, etc........and I knew I was on the line because there's an old barbed wire fence down it. It's up enough spots I can find it and mark it or trees next to it.)

Now...........if (IF IF IF) I can somehow get to the exact NE corner/waypoint, I should then be 880 yards from the NW corner while simultaneously being 440 yards from the SE corner/waypoint. I know that's correct, but getting to that point is the first problem. So here's my questions:

1) I have a marked straight line down 1/2 of the Northern boundary line. How do I use a GPS to continue that path exactly, through thick woods, and walk a straight line without getting too far off course, since I don't know the GPS coordinates of where I'm headed?

2) One I somehow accomplish the problem of finding the NW corner.........and know the GPS waypoint of the SE corner........I should be able to walk the correct path of the Eastern boundary and head to the SE corner/waypoint........ RIGHT?? I think I know this one.

#1 is what is throwing me. I know how to tell once I'm there........but I don't know how to use the GPS to help me get there. What I'd LOVE to know how to do is take the GPS coordinates of the first 3 corners, and extrapolate the GPS coordinate of the NW corner, and then I could walk straight to it.

Ideas? Help????