Need to survey a road for an aligment survey. Problem is traffic is dangerous for rodman to walk in the centerline. Prismless is out of the question as signal will just reflect off passing cars.
I was thinking of mounting a GPS through the service's vehicle sun window & drive it slowly down the lane for several roundtrips to get several overlapping datasets.
I am worried about the bouncing effect of the car as the elevation of the RTK points will follow the bouncing pattern of the vehicle. Maybe a slow drive will eliminate if not minimize this error.
Anyone done that using RTK/PPK? Feedbacks?
I wouldn't recommend it for that use... I've done it before but the results didn't need to be nearly as tight. Our intent was to find a bust of a few meters or so in aerial LiDAR flight paths. It worked well for that but the results are definitely hit and miss. Running through your sunroof, how would you get an accurate vertical offset for your rod height? We have a mount system that goes on the side of the truck, fully exposed.
I have drove one before , mounted on a mag mount over the rear tire. No good for elevation, and the line was halfarsed. I would study the traffic flow at night, come up with a plan to try to have your guy walk it with a couple of trucks shadowing him.
When I have a busy road or intersection to survey, I will try to schedule it early on a Sunday morning. It sucks working on Sundays, but the traffic is generally much lighter, and much safer.
very true, Jimmy.
Franz-
Sounds like a government contract ?
Ergo, any hope of police escort with lights flashing with "safety" as
your obvious concern ?
Cheers,
Derek
I agree 100% with Jimmy. It does stink working on a Sunday, but it is most likely the best solution to your problem. We had one similar to this years ago but it involved trying to get approval from DOT for lane closures to measure inverts in some storm manholes. He looked at our issue and was the one who actually recommended doing it Sunday "under the radar".
Test it, see what you think, you are the one who knows the tolerances for the job. I doubt you will like the results. Get some shots in a parking lot or somewhere safe and relocate them with the instrument, see how the elevations check, my guess is about 3cms, good stuff for raw dirt, not so good for concrete.
We usually do heavy traffic sites late at night, say between 2 and 5am
Have you asked the agency if they are willing to provide traffic control?
I'm thinking a rolling traffic control similar to when they stripe the roads?
mobile lidar.
Lidar is out of question, expensive & would meet same traffic obstructions.
Thanks for the inputs guys. Will discuss it further with the project team.
As for accuracy I surveyed some bitumen streets in a local town last year and as it was only for flood control dtm I wasn't too concerned about super accuracy.
I've a 5/8 bolt on a roof rack of my Ute (wagon) and have used it for many RTK jobs.
As it was on c/l side I drove as near as possible to it in both directions.
I stopped at a few places then came back and repeated same with the pole mounted GPS.
I was amazed that at the sampled places I consistently was within 25 mm of the vertical.
It gave me confidence that under circumstances that made walking the road difficult accuracy can be had with some confidence in the results.
yes, 25mm sounds just what I get also, we spend a lot of time checking continuous topo, it's easy to do.
I mount the Seco Truck rack on the drivers side, mount the R6 on the rod in the rack use continous topo on the TSC2 with a 20' interval and drive slow with all the lights on. Granted these are wide open rural roads and not 4 lane freeway so lane closures are not warrented when the only traffic is an occasional car or deer crossing the road. I have gone back and shot specific points like the crest or sags of hills and we have been getting vertical error of 0.1'*/-. These are large tracts where we might have 12 driveways in 2 miles.
I usually drive both edge of pavement and the C/L and I can do a mile in about 20-30 minutes. We paint the start/stop points and the three across usually line up pretty good.