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I am using ogr2ogr to reproject a shapefile. Here is what I have done.

  1. I have a shapefile A.shp. I used the following command to create B.shp: ogr2ogr -t_srs EPSG:3857 B.shp A.shp
  2. Now I reprojected B.shp again and created C.shp ogr2ogr -t_srs EPSG:3857 C.shp B.shp

Since B and C have same data and they are in same projection, I think they should completely overlap. However the do not. In the image bellow the Red one is A.shp and the other one is B.shp.

Is there a good reason why this can happen? This is happening to all the shapefiles not just this one.

enter image description here

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You might get a shift if the source CRS of the original shapefile is not given by an EPSG code, but a .prj file. These do not include datum sift parameters, and gdal tries to match the WKT information with its own EPSG database.

So I suggest to always add the -s_srs parameter for all ogr2ogr operations.

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  • So, do you mean that the information in .prj file is not sufficient to do the reprojection?
    – Mohayemin
    Apr 29 '15 at 10:45
  • If it is a CRS that has a datum shift (+towgs84 different from zero) in the EPSG code, it is not sufficient.
    – AndreJ
    Apr 29 '15 at 11:02

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