I have a PDF of a contour map of value Z for an area. For the same area, I have a set of points that I would like to match with Z values interpolated from this contour map. For an individual point, this can be "eyeballed" pretty easily, but I would like to do this for a few hundred points so I am looking for a more efficient way of doing this using for instance Google Earth, arcGIS, r, etc.

I am aware of the ability to overlay images in Google earth and draw lines on a map to export as kml files.

This seems like a reasonable place to start but it seems overly tedious to import these lines into r separately and write some algorithm to interpolate between the lines.

I am wondering what workflows and existing tools people are aware of for this type of problem since I have struggled to find much.

I am very new to working with GIS data.

  • 1
    Very interesting, Do you have some small example data to get an idea of the "individual eyeballed pretty easily" and " more tedoius" stuff.
    – huckfinn
    Jan 7, 2016 at 23:51
  • Here is a link to the same image I am working with: wiki.aapg.org/File:M97Ch4FG10.jpg. Mine is slightly higher resolution but otherwise the same. You can ignore the dashed lines representing faults. I have a collection of well locations throughout this area and I want to automatically obtain the approximate gross thickness based on location within this map.
    – jmont09
    Jan 8, 2016 at 13:18
  • I ended up using arcGIS for this. The approach was as follows: 1) georeference a .png of the image, 2) create a shapefile/polyline and trace each contour in the map, 3) I added a field/attribute to each polyline where I input the value at the contour. 4) Using spatial analyst I used TopoToRaster. 5) Finally I extracted from this raster to the layer with the points of interest.
    – jmont09
    Jan 15, 2016 at 22:56

1 Answer 1


If the contours in the PDf are vectors rather than an image based pdf where they are just part of an image you could export the lines to QGIS via DXF using Inkscape. You would need to sort out the georeferencing which might be easiest in a CAD package such as draftsight. Once in QGIS you would need to save the lines as a shapefile and then add an attribute column for the heights and manually add the heights for each line. With the elevation information attached to the contour lines you could then interpolate a raster grid (terrain model) and use a function that reads the height value from the grid to the attribute for each point. If you are not used to the various bits of software you would need to do some research at each stage and you might be best to continue with you manual method though you could use linear interpolation to make that more accurate.

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