I've seen this asked and occasionally answered on the site, but none of the solutions applied. I am attempting to intersect points (i.e. NYC Motor Vehicle Collisions) to a polygon (i.e. a shapefile of the Bronx). When I do this, QGIS returns an empty shapefile. I have done this exact operation in arcmap without issue.

The CRS are different for both files, but I have one projected visibly over the other. This should be a simple intersect w/2 files? What am I missing?

  • Which specific tool are you using? Perhaps a screen shot of the inputs would help – Pura Vida May 20 '16 at 23:49
  • 2
    Project one into the other's coordinate system. – Vince May 21 '16 at 1:10

As an addition to vince comment: The tool in ArcGis has the reprojection as an extra step before the processing built in, you don´t see this(beside in the documentation). Qgis does not, and the standard tool does not warn you either (the grass tool for example tells you about it). When they are visibly onto each other it is just on-the-fly transformation. This is not as accurate and therefore not used for calculations. You have to live with that until Qgis changes the tool... Or you might put the to steps into the graphical modeler and get a tool that does it in one go without creating extra files.

And as sidenote: Watch out for the reprojection in general, there is more "science" to it than the easy use of the programs suggest. Depending on the needed accuracy and the eventually involved transformation (when the CRS are using different reference ellipsoids) the different programs might have different outputs in the range up to 1m.

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