Grid vs Surface

[mnorton]

Our work is in surface coordinates but I have data in grid coordinates.  Is there a process in Civil 3D to make that conversion?

[Anonymous]

Do you happen to know the Grid-to-Ground scale factor?

[mnorton]

Yessir.

[mnorton]

The grid data I referred to are contours. I scaled the data using the reciprocal of the surface-to-grid scale factor.  They scaled fine horizontally but the problem, of course, is that they also scaled vertically.  I've used Map's coordinate conversion before but I'm not sure this situation is actually a fit for that tool.

[mnorton · Accepted solution]

Got it.  I inserted the contours as a block into the drawing and set the X and Y scale factors to the reciprocal of the surface-to-grid scale factor and left Z=1.

[Pointdump]

Mike,

Not to throw cold water on your solution, but the Combined Factor (Grid Scale X Elevation Scale) is not constant. If you use GIS Data, like Contours, you might want to consider using a <<<Custom Low Distortion Projection>>>. Civil 3D can then easily convert your data to project coordinates.

Note: At the bottom of the page at this link you'll find 2 PDF's and a Powerpoint on the subject of Grid-to-Ground by the late Sinc.

Dave

[mnorton]

Hi, Dave

Sorry for the delay in response.  We've been a little busy with some water down here.  Did you happen to see my thread with Jeff_M?  He was gracious enough to hook me up with "Working with Grid Coordinates" and "Solving Grid to Ground Problem".  I may have this PowerPoint as well but I'll review it all again.  I must warn you:  I may have questions.  Lots of questions.