Settings for VRS RTK using Trimble R12 and Access

[jimcox]

Pretty much certain to be a coordinate system issue

What coordinate system are you using?

What coordinate system is the VRS running on?

You can probably get around the problem using a site calibration on known points

— later

I’ve had a quick dig

I see SCRTN uses Trimble receivers – this suggests it is also using the Trimble standard definition for SC 3900 – which turns out to be NAD83(2011) – a time dependant transformation with a 2010 reference epoch .

I’ve had a look at Opus, but could not confirm if its numbers are straight NAD83 or NAD83(2011)

The size of the shift you are seeing suggests it might be the former…

[davidgstoll]

Hi Eddie,

In Greenville, South Carolina, State Plane coords, the difference between US Survey Feet and International Feet is just under 4′.

The shift will be to either the Southwest or Northeast.

Dave

• This reply was modified 4 weeks, 1 day ago by  davidgstoll.

[Eddie]

Dave,

Thanks for that information. Do you suggest that I set up my Access job using International Feet in lieu of US Survey Feet?

Below, are the settings for SELECT COORDINATE SYSTEM in my Access job:

System: US NAD 83, Zone: South Carolina 3900, Local Datum: NAD 83 (2011) (Mol), Global Reference Datum: NAD 83 (2011), Global Reference Epoch: 2010.00, Displacement Model: HTDP V3.4.0, Use Geoid Model: YES, Geoid Model: GEOID18 (Conus) (g18us.ggf), Use Datum Grid: NO, Coordinates: Grid, Project Height: 900sft

• This reply was modified 4 weeks, 1 day ago by  Eddie.

[OleManRiver]

Sounds like international feet bs is survey foot for South Carolina to me. Make sure in Trimble access in units are set to feet not us foot. To truly check just use the meters at first and see if you still have the shift. If not then that’s the issue. If you still see the shift. I remember a long time ago that topcon has a setting called wgs84 no trans. That not being set caused issues when topcon recovers ran on a non topcon network.

[davidgstoll]

Eddie,

It’s been a decade since I last used Access, so I don’t know what coordinate systems are available these days.

I’d go with EPSG:6570 NAD83(2011)/South Carolina(ft) if it’s available in your data collector. All the cool kids are going to International Foot units.

Dave

[lurker]

Eddie as others have said, you are using US feet in your data collector while South Carolina operates on international feet.

For the purposes of the South Carolina Coordinate System, the foot is the International Foot with one inch being exactly equal to 2.54 centimeters.

[Eddie]

Yes, that certainly explains the cause of my X-Y coordinate shift issue, so I’ll make the change to IFT. Do I also need to set up Access to use IFT for ELEVATIONS? Thanks for your help, -Ed

[davidgstoll]

Sassafras Mountain, in the Blue Ridge Mountains, is the highest point in the state of South Carolina. Elevation 3554′.

The difference in elevation there between the 2 foot units, 2ppm(*0.000002) is only 0.007′.

I might be wrong, but I think elevation units are always going to be same as the horizontal units when you select a coordinate system.

Dave

[Eddie]

Yes, I have confirmation from a good source that South Carolina uses IFT for X, Y and Z.