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I am trying to run a point-in-polygon count in QGIS. I have a shapefile of San Diego zip codes in NAD83 (2230 EPSG). I have a delimited text file of points with lat/lon coordinates.

In QGIS, I can get the points to overlay properly on the polygons in the viewer in the basic OTF projection. But I can't run the point-in-polygon count while they're in different projections. I have reprojected each file (saving the points as a shapefile) with identical projections in QGIS, but the geographies don't match up at all.

I'm assuming my issue is that the lat/lon coordinates are in degrees and the NAD83 projection is in feet. I thought that reprojecting would solve this issue though? Clearly the files can be easily read together, they show up in the right place in the viewer with the OTF projection. This only works with a default custom CRS for OTF that appears to be handling the ft/lat-lon conflict. If I save all in a WGS layer like EPSG4326 or EPSG3857 then nothing aligns.

Here is the text for the projection that is working:

    * Generated CRS (+proj=lcc +lat_1=32.78333333333333 +lat_2=33.88333333333333 
+lat_0=32.16666666666666 +lon_0=-116.25 +x_0=2000000 +y_0=500000.0000000001 
+ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=us-ft +no_defs)
mmalloy
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    This question would be much more on-topic at the [gis.se] Stack Exchange. – PolyGeo Aug 16 '17 at 12:56
  • When reprojecting are you applying the proper transform or are you simply redefining the projection? – Andrew Reid Aug 16 '17 at 18:20
  • @AndrewReid I am saving the shapefiles as new files with the same CRS, which is I understand it is sufficient for a full transform, vs. reprojecting in the project window only. I'm relatively new to mapping, but I've always been able to solve CRS inconsistencies by saving a new shapefile in the same CRS. I haven't been able to find any online resources demonstrating a process for transforming coordinates vs. simply saving the file in new projection. – mmalloy Aug 16 '17 at 19:25
  • @PolyGeo Thank you, I didn't know there was a separate GIS site. – mmalloy Aug 16 '17 at 20:56

1 Answers1

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Found a question with this answered already here: https://gis.stackexchange.com/questions/13023/how-to-change-the-unit-of-measure-from-degrees-to-meters-in-qgis

Also further information here: http://urbanpolicy.net/wp-content/uploads/2014/05/TIGER_file-prep_140509.pdf

mmalloy
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