Georeference a polyygon within a pdf file

by delmalki   Last Updated June 01, 2015 23:09 PM

I have this pdf file that contains a specific borough of my city, Montreal, with a polygon inside it. Link to pdf file: PDF FILE

The jpeg image once exported from the pdf file is the following

enter image description here

I am trying to extract the red polygon and georeference it.

I have tried using QGIS to open the image file and then manually add coordinate points to specific portion, but it seems tedious and long as I have around 90 different pdf file that I aim to georeference.

Is there an easier way such as taking an actual map of montreal and overlay this map on top of the previous one, and then automatically georeference it?

I don't know if it can help you but the actual pdf file is a vector, when I opened it using illustrator I was able to check or uncheck the red portion.

The ultimate goal is to transform this red polygon into a geojson file. I don't mind doing it manually if theres an efficient way but I would be even happier If there's was some way to automate this through a script.

I have been looking over the past week on the internet for georeference tutorials but most of them are for raster images and do not take in account pdf file (vectorized), I mean in theory, in my opinion it seems possible to compare 2 vector file, mine and lets say the whole vector file of montreal and then georeference it automatically.



Answers 1


If these are geopdfs then you should use gdal and convert to vector and you would be done. If they are just PDF then they may or may not contain vector data still. Trying opening it up in Inkscape and save as a dxf. Bring the dxf into Arc and see if you get you polygon. Doesn't look like you have any coordinates on these maps unfortunately, but once you figure out the projection you should be able to snap road intersection from your dxf you created to the same intersection from projected data. Just use the georeferencing toolbar And 2 points should do. I built a tool based on ghostscript for this a couple of weeks back.... Unfortunately the company I work for owns that now, but Inkscape work easily.... Better then digitizing anyways.

Mike
Mike
June 01, 2015 20:14 PM

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