I need to georeference a PDF map and digitize the features on the map into a shapefile using WGS84.

Is it best to georeference the PDF map and digitize the associated features in a local projection system, such as a state plane projection system, first and then later convert the final shapefile into WGS84 or should I just be using WGS84 from the start?

I am asking as I want to minimize distortion and insure that the final product is as accurate as possible.

  • 3
    I don't believe that it is essential. The errors in measuring the ground control points are in any case bigger than the inaccuracies in coordinate transformations. It may be more convenient to digitize if you use the local system that is native for the map because then the map won't stretch and rotate much.
    – user30184
    Nov 28, 2022 at 19:36
  • You had tags for QGIS and ArcGIS Desktop but did not mention how either is relevant to your question in its body so I removed them.
    – PolyGeo
    Nov 28, 2022 at 20:01
  • 2
    There isn't a choice here. The projection was chosen when the map was created. You need to georeference in that coordinate reference, then project afterward.
    – Vince
    Nov 28, 2022 at 21:43
  • You probably have checked this but I'll note many pdfs are georeferenced, and as such you could add it directly to QGIS and it should show up in the correct location as a raster, but with some luck and with pdf layers enabled even provide some vectors for you.
    – John
    Nov 28, 2022 at 22:08
  • How would you use georeference your PDF map ? No mention of export to jpeg or TIFF to georeference it ?
    Feb 20 at 1:00

1 Answer 1


Georeference in the best matching coordinate system. Digitise in that coordinate system and then reproject/transform to WGS84.

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