Just wondering how accurate a topo you can get using a PM2 in Stop and Go mode? What sampling rates do you use? 1-2 bases? etc... I have searched the archives but haven't really found an answer on the accuracy issue - I may have missed it. I have been tempted to use it several times lately, but without any of the above information, I have been unwilling to risk it (of course, the job has to be out pronto, not allowing for a return trip). Any advice, techniques etc... would be greatly appreciated.

I just got back to the office from reshooting a topo that I did last Fri. Where, I used 1 base and 2 rovers. The problem was that 1 rover everthing passed with good vectors and the other rover just about everything failed with a partial solution or worse floated. So, I went back today and shot everything with a total staion. I'll check that points that were good and see if there is any difference.

Several years ago I did a topo of an orange grove near my house in Florida with a total station. Took about a week, very hill property in central florida with about 45 feet difference from high spot to lake.

I performed the survey by laying out a set of hubs along the road at every 4th tree row and took shots down the row until I couldn't see anymore, then set a nail, moved ahead and continued shooting. Got to the end and set another nail to check later. Then back up to the road and do it again. About a third of the lines needed me to move up three times and the rest I moved up twice. Got a great topo from that work

Went back a couple of months ago and did the same topo plus the other 40 acres right beside it, total 80 acres of topo. This time I decided to do it kinematically. I built a rod holder to hang from my truck door and had my wife check the HI with me in truck and the antenna up pretty high, (enough to get above the trees). this left the PM2 a little above the window of the truck and facing down.

I initialized and started driving the entire property taking "shots" at every two second interval. I ran EVERY tree row instead of every 4th one and never lost lock or stopped the topo, just driving back and forth, drinking coffee, listening to the radio, counting my blessings, etc...

After driving the entire site I reinitialized in stop and go mode and checked all those nails I had set down by the lake in 1999. I also located the lake edge, shot the additional proerty corners we had found plus some additional nails for future backsite use if we need to reset anything with Total Station. Done by 3:30 in the afternoon.

After processing data and creating new topo the new conours overlaid the old survey and were almost perfect until you got down by the lake. I differed with my old topo by about a tenth vertically and a couple of tenths horizontally, (figured to be little out horiz 'cause we were originally stacking a lath for backsight when we did the Total Station Survey) when i got to checking the nails down by the lake.

Next Day I run a level loop from road to lake and check into my nails by the lake and guess what, the GPS points were hitting with in a couple of hundreths and the old total station stuff was out a little more.

Try this stuff and stretch the envelope, it works really well.