Pee Dee GIS Users Group

In 2022, National Geodetic Survey will go to a new datum that will be geometric and geopotential.  It will be geocentric, satellite based, and not based on the existing national monument system.  It will also incorporate velocities in some fashion.

Matt Wellslager, Director of the South Carolina Geodetic Survey is seeking feedback from the various stakeholders that use the datum system, surveyors, SCDOT, the GIS community in general and county tax mappers in particular.

Your feedback is solicited for the following questions:

1)      Does South Carolina still need a State Plane Coordinate System?  (NGS is looking at options regarding the continued support for state plane coordinate systems.  Considerations are to adopt a low distortion projection.  This would be done in an attempt to reduce the difference between ground and grid values.)

2)      If so, should the current values for the current State Plane System be preserved? (This means that Northing and Easting would remain the same and the underlying Lat and Longs would shift with the change in the datum, and would continue to shift over time with the accumulation of velocity.)

3)      If the State Plane System values should shift with the new datum, should it be a big shift or a small shift? (The new Lat Longs will shift on the order of 1.5 meters initially, and then have a westward velocity of around 1.5 cm/year.  If the State Plane coordinates just shift with the Lat and Longs, then they will only be about 1.5 meters from their current values.  Some folks argue for a larger shift, since the originating Northing and Easting is an arbitrary value, anyway.)

Regardless of what we want the State Plane system to do, elevations will change, downward .25 meters in South Carolina, which coincidentally, puts us back to elevations very close to the 1929 NGVD.

This is a chance for South Carolina Surveyors’ opinions to be heard when a report is made to NGS before the end of the year. Please respond to matt.wellslager@rfa.sc.gov with your comments and I will compile them in the next couple of weeks.