Hello,
I'm pretty new to this website and I'm sure this discussion has come up more then once before so I apologize in advance.
I've been a Party Chief for over 5 years now and we recently acquired a new R.P.L.S where I work. Before he came along I was using Grid to collect my datum. We do a lot of subdivisions and civil engineering as well as expert witness accident scenes. Here locally our monuments are on the Grid system from the local River Authority. Most firms also seem to use Grid as far as I can tell. I've never ran into any sort of issues from other surveyors when my data is being used in the construction phase. Our projects are usually within a 1 mile radius. I was told when a job stretches in excess of 5 or more miles it may be a good idea to convert to Ground.Ā
I just want to reach out and see what most of you use and why?
Is it worth spending 2 days of static sessions to envelope the job and be on surface?
Couldn't you just adjust your Grid to Surface in CAD with a known point scale?
Anything I should be aware or concerned with either or?Ā
Thanks
Replies
We use Topcon Magnet, which has a ground/grid ..Our elevation is anywhere from -10' to 1500'. The DOT uses grid and so do the utility companys. Grid is basically state plane coordinates. In topcon you can switch easily. When retracing any survey we have to be in ground.Ā Ā
I use CORPSCON to get an average scale factor and scale all of my RTK data before I use it. I am in Texas South Central Zone. The SF is 1.00013...Ā A 1000' line of grid will actually be 1000.13' at the surface. At a mile it will be 5280.69' That's too much to ignore.
We do a lot of rural surveys that are very large. You will never match the old field notes without applying the scale factor.Ā
The scale factor on a construction site will probably have little difference.
Ā Grid north in ground distances is whats typical in my neck of the woods, at least when working with the state or DOT. However I'm at 3800' or higher here in NM, so the typical ground to grid scale factor is at least 0.9999...that means at a mile there's almost half a foot difference between the two and for any type of engineering or construction work on a site larger than a few hundred feet grid distances don't cut it. If you're closer to sea level grid and ground will be much closer so that may be why under a mile is ok in grid for you.Ā
600'-1100' Here in Central Texas. However most jobs are in the realm of 100' elevation and no more then a mile long with the receiver being in the middle of the job. I guess doing an extra 3-4 statics isn't a big deal but I was using 1 session and then setting benchmarks or line sets from it with levels etc. Ill take it for what its worth and can only learn more which doesn't hurt anyone. I was just concerned we would have to bid up jobs and possibly lose clients to competition.