So John.... now you have many somewhat expert opinions on your project fieldwork. SO please share with us.... How many hours did you estimate it would take?
Well, I originally estimated 120 hours in the field. I had to cut that back slightly when negotiating with the client (federal government). But, once we got out there we found that the terrain was REALLY messed up, not very many areas so far have been natural ground. It was probably used as a dump for not only slag (steel mill waste) but construction debris, dirt, whatever. Lots of small piles spread around, as well as some huge piles we knew about. If it turns out that we go over in time, I can use that as a justification for asking for some more due to the conditions, which no one at the clients office was aware of either. I rarely ask for a modification, so they are usually receptive if I have a good reason, although I don't like to do that. Some A/E contractors routinely ask for modifications, but I have not had to do that hardly ever.
At this point, we may be OK time wise, it will be close. I believe (hope) that we did the toughest areas first, in which case it should get easier and we may meet the time estimate.
Here is what it looks like, note that the underbrush is vines/briars about 4 foot high. Not too hard to shoot over, but the rodman still has to fight his way through it. He basically walks with a swinging machete in one hand, the rod in the other. Fortunately he is a bit younger than me and more athletic. Even though we use a robot (S6), it is still necessary to have me at the gun to just keep it pointed in the right direction, it constantly looses lock due to the trees, etc. Really speeds things up.
Here is a quick, unedited 1 ft contour map of one area we have done so far. Note that the areas shown in red are the bottoms of holes, not the tops of mounds. That area on the east side is several deep holes that we couldn't even see until we got down in there. The whole eastern edge is solidified slag that was dumped molten.
Here is that same area outlined in red on an older 2 ft contour map (given to me as a pdf):
This particular site is not one that you can leave the robot unattended. The second man also sketches and holds shrubs out of the way. I wouldn't feel safe at all working there alone. I've already had someone throw a 3-4 pound rock at me from a high hill while my back was to him.
Job Completed!
OK, so it was way worse than I had anticipated, but we finally completed the topo. The open areas were easy-pretty smooth, easy to do RTK in. The wooded area was full of piles of material as well as several deep holes (with no outlets for water to flow out), all covered with thick vines and briars. I learned that slag is a very porous material, so water is just absorbed. We never ran into any mud or streams in there, or any water at all, despite being there when it was raining hard.
So, here are our traverse points:
Next, all of our topo shots (RTK and total station). Note that the piles/holes required a lot of shots to properly model.
A 1 ft contour interval map:
As I mentioned, there was lidar from 2006 (statewide, 2 ft). Here is a map showing the differences between our points and the DTM from 2006. The open area on the east was obviously changed (previous fill), and the road on the west side was graded in. The ditch surrounding the site was not there at the time. As can be seen, several large features (both mounds and holes) were not picked up by the lidar.
The orange colored almond shaped area just to the NE of the center of the job is a large mound. Here is a zoomed image showing our contours (black) and the 2006 contours from Lidar in blue. Not sure how that was missed:
and a 3-D view of the differences (red is ± 1 ft):
All-in-all, a very interesting project. Hardest topo I have ever done.
Job Completed!
So how did your time estimate of 120 hrs work out?
Interesting, the differences between ground and lidar. Is there any chance that the ground changed since 2006?
Job Completed!
Not in the interior. I believe the differences are due to foliage and thick underbrush.
As for time, I requested some additional hours after the couple days out there when we discovered how many small piles there were. We were pretty close, maybe went over a bit in the end. The part we left for last (lighter woods) turned out to be the worst due to briars, etc.
