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How To Convert Linework From Surface To Grid Coordinates for KMZ/KML Exports.

Bringing in geolocated files to SiteMarker is as easy as dragging and dropping the file onto the map. Sometimes these files come into SiteMarker in the wrong place, checking the coordinate system is the first place to look. 

 

SiteMarker accepts geographic data in grid coordinates. If your AutoCAD-exported KMZ/KML file is misaligned in SiteMarker , it's likely due to:

Incorrect datum settings in the "MAPEXPORT" command, or

The drawing being in surface coordinates, not grid coordinates.


This guide walks you through converting linework from surface to grid coordinates in AutoCAD.

Instructions:

1. Open Your AutoCAD File

Open your surface coordinate file (main file).

Confirm that the surface-based linework does not align with aerial imagery or expected reference points. At this point you may have already exported the file once, uploaded it SiteMarker and noticed linework is not located properly. 


2. Identify the Scaling Base Point

Determine where you will scale from:

Option A: Use 0,0 as the base point (Confirm with civil team)

Option B: Use a known site center or benchmark (e.g., a control point, Confirm with civil team)

Note: Ask your surveyor or civil engineering team for this information if it is not clear where the base point is located.

3. Locate Scale Factor 

If you're working on a specific engineering or survey project, the CFS is often documented in:

    • Project survey control reports

    • Engineering drawings or notes

    • Surveyor-provided metadata with the control points

Look for terms like:

    • Combined scale factor

    • Grid to ground scale

    • Surface adjustment factor

If you are not able to find the Combined Scale Factor, you can use this website to calculate your scale factor: https://www.ngs.noaa.gov/NCAT/

4. Apply the Scale in AutoCAD
  • Select all line work: Type "SELECT" -> (choose all)
  • Activate the scale command: Type "SCALE" -> press enter 
  • When prompted for base point either: 
    • Select the known base point on the screen
    • or enter, (0,0,0)
  • When prompted for scale factor enter:
    • Scale factor located in step 3
5. Export to KMZ/KML

      How to Export a KML/KMZ

6. Upload to SiteMarker & Verify Linework Alignment 

Now you can upload the corrected .kmz or .kml file to Site Marker as a map layer. The linework should appear precisely aligned with aerial imagery.

Notes

  • Always confirm datum and projection system before exporting.

  • Different regions have different scale factors—do not reuse across projects.