Ground to Grid NAD 27 to NAD 83 Virginia State Plane

[RobMinford]

Good Afternoon,

Is there a standard conversion value available for meets and bounds written with NAD 27 to NAD 83, specifically Virginia State Plane?
My ad hoc ground to grid conversion is close, but I want something to check it against. Currently my offset is 7-22-10, Distance Factor of 1.

Thanks,

Rob

[MelitaKennedy]

Good Afternoon,

Is there a standard conversion value available for meets and bounds written with NAD 27 to NAD 83, specifically Virginia State Plane?
My ad hoc ground to grid conversion is close, but I want something to check it against. Currently my offset is 7-22-10, Distance Factor of 1.

Thanks,

Rob

Hi Rob,

I think I'm not going to be able to answer this, but let me try to get some more information. I normally see ground-to-grid (or vice versa) conversions applied to a single SPCS zone.

NAD27 to NAD83, not counting any projections, is a geographic/datum transformation. In the US, that would use the CONUS grid files from the NADCON method or software.

Are you converting between NAD27 Virginia which-zone? and NAD83 Virginia state plane? In US feet or meters?

Is the offset a bearing? Azimuth-from-true-north? Angle between the two grid norths? Or some other basis-of-bearing?

I haven't heard of a distance factor unless it's grid-to-ground or the scale factor at a point (point scale due to the projection distortion).

If you're converting between two VA SPCS zones, and you have the grid-to-ground values, we may be able to set up a regular reprojection between the two by incorporating the grid-to-ground values into the coordinate system definitions.

Melita