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I have a geographic file (be it shapefile or otherwise) which is stretched and dislocated into the wrong projection space.

So I'm wondering how to approximate its correct location by selecting points on this file which correspond to real-life locations in the given basemap, and use this knowledge to correctly geo-reference it in the way we would with most raster images?

Taras
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Anna
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    Before going this way, I'd try to figure out the real projection of the file and assign this crs to it. – MrXsquared Jan 26 '21 at 00:41
  • I have, but it didn't work with any fruitless or futile search, and seems only to be an approximation anyway. Besides, I suspect this may be quicker and in any case, the co-ordinates are off (shunted to the side of) so I will need to re-align the projection anyhow – Anna Jan 26 '21 at 00:45
  • See: https://gis.stackexchange.com/questions/33208/georeferencing-vector-layer-with-control-points-using-qgis There are a few correct answers there. – HeikkiVesanto Jan 26 '21 at 01:15
  • @HeikkiVesanto thank you, do any of these replicate the ease and simplicity with which we can now import an image onto QGIS project file for viewing and distortion purposes in terms of usage and basemap layer? – Anna Jan 26 '21 at 02:00
  • Normally this type of error happens when we mistakenly entered a wrong CRS. Can you try to find the correct CRS ( coordinate reference system or projection ) and correct it with in the properties of the shape file. – Uditha Herath Jan 26 '21 at 02:33
  • @UdithaHerath No, in my case it happened because the shapefiles were made from a georeferenced raster image. However, when plotting out the co-ordinates, the original author did not perfectly align their points. I don't want to start over again since that would involve too much work, and I am unable to regardless, as the original information about their source data is now gone. Besides, I imagined a simpler answer must exist to ease this resolution to its inevitable conclusory stage, in order to move those points together to match with the required transformations. – Anna Jan 26 '21 at 07:44
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    Try to use Georeference a shpefile with use of qgsAffine Plugin or Vector Affine Transformation Plugin by Mauricio de Paulo and Erik Timmers. https://plugins.qgis.org/plugins/qgsAffine/ – Uditha Herath Jan 26 '21 at 08:27
  • @Anna I would read the answers, but none of them are as easy to use as the Raster Geoferencer. But they are your best options, unless you want to buy ArcGIS, where the Spatial Adjustment tool would do what you want. See: https://gisforthought.com/georeferencing-vector-data-using-qgis-and-ogr2ogr/ – HeikkiVesanto Jan 26 '21 at 09:51

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Since QGIS 3.26 this can now be achieved with the georeferencer, same tool that is used of raster georeferencing:

"QGIS now supports georeferencing vector layers in the georeferencer tool. This allows vector layers without spatial referencing to be interactively georeferenced, or layers with referencing to be re-referenced, in a similar manner to raster data. Georeferencing occurs in a task, so QGIS should remain responsive, even with large datasets."

https://www.qgis.org/en/site/forusers/visualchangelog326/index.html#feature-georeferencing-vector-layers-in-georeferencer

HeikkiVesanto
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