Thanks for checking out the SPC zones. We use the Florida SPC east zone. We typically set control points two hundred to five hundred feet apart.
The Florida East zone is close to being an LDP. At 500' with the type of numbers the East zone uses maybe .03' between grid and ground. It all depends where you are with regard to the central meridian. Elevation shouldn't matter much there.
I don't know what field software you are using, but many of them will allow for computing scale factors for total station setups/observations on the fly, to bring those ground observations to grid.
We use Topcon MAGNET Field. Is bringing ground observations to grid the only approach to use when mixing the GNSS with a total station? Is this because we want everything referenced to the grid, or do we just want to eliminate any difference in distances?
Is bringing ground observations to grid the only approach to use when mixing the GNSS with a total station?
Either that or bringing GNSS measurements to ground.
Or, where the difference is minimal, sometimes it's not worth worrying about.
Is this because we want everything referenced to the grid, or do we just want to eliminate any difference in distances?
Well, there's never going to be a total elimination of difference. Distortion is a fact when working with projections, whether in grid or ground. We can usually minimize it to the point that it can safely be ignored, however.
As far as whether you want everything referenced to the grid? That's up to whoever is running the project.
I don't see how gound/grid is your issue with FL East Zone, you start with 60PPM at the central meridian and it decreases from there.
Even if you're at the Florida high point it only adds 15PPM.
Your issues are measurement techniques, those need to be tightened up, both GNSS and TS.
I would only survey on the State Coordinate system there since it's basically an LDP anyway.
In 500' expect to see a difference of a few hundredths (3) of a foot. I'm pretty sure Topcon will handle the ground to grid conversions with your TS, I know I can with my Topcon TS although I hook up Trimble DCs to it.
It appears your GIS people are attempting to create a perfectly stitched-together map of your work area by using State Plane coordinates. Direct total station results will not match State Plane unless you are in an area where grid and ground are effectively identical, which is not at all common. If you were in an area where the difference was roughly three inches per half mile, two points two miles apart would have a difference of one foot. When your GIS people receive surveys that are based on ground values, they find they will not perfectly mate up with your grid values.
As far as whether you want everything referenced to the grid? That's up to whoever is running the project.
Do you have a preference when performing a boundary survey? We're expanding our search for property corners on one project, along with section and quarter corners. This project is for proposed sidewalk construction in an almost one hundred-year-old part of the county. We're having trouble making the right-of-way fit, so now it's turned into a boundary survey. Does the fact that we're throwing section and quarter corners into the mix dictate how everything should be referenced? The software we're using does have a grid to ground option, but we don't use it.
Your issues are measurement techniques, those need to be tightened up, both GNSS and TS.
That's only partially true, because I have complete control over the TS. The GNSS is a different story. We use RTK, but our rover is old (GPS and GLONASS only), and we only perform one observation session per control point.
The software we're using does have a grid to ground option, but we don't use it.
If you did use it you could survey in ground coordinates with both GNSS and total station and export grid coordinates for your mapping people. When importing or exporting state plane coordinates make sure grid is checked on the import/export screen. TO cross check the coordinates in the import or export files should match the grid coordinates in Magnet. You can easily flip back and forth between grid and ground coordinates on the points screen. But always make sure you are in ground when surveying. You can also do cogo inverse in Magnet in grid or ground. Around the Daytona Beach airport 5280.00 ground dist is 5279.71 grid.
One RTK observation is inappropriate for control. There's most of your 0.10' errors.
But always make sure you are in ground when surveying.
Thanks for your advice.
One RTK observation is inappropriate for control.
I agree.
