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I am working on a project mapping Rockingham castle for a event help there in August and am mapping the layout and camping area. I'm looking at taking over from the person previously performing this task as he is busy this year.

He has done all the work AutoCAD, whereas I work in GIS, mainly ArcGIS. However my license at home will expire in the future so am trying to start using QGIS and I am on a mac.

I acquired OS Mastermap vector data of the area and sent it to him as a dwg file exported from ArcGIS shapefile.

My main query is how does he align the un-georeferenced dwg file he has used to create the layout to the OSMM and then assign OSGB coordinate system to the dwg layout file and export so that I can import it back into QGIS or ArcGIS? He works in AutoCAD mainly but has Civil 3D at his work.

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He can use a command in AutoCAD called ALIGN to geo-reference his existing drawing.

He will need to copy in his existing work into the OS dwg you have sent him. He can then select all his work, use and the ALIGN command to line his drawing up with the OS data. This will only work if there are a couple of reference points in his existing drawing that correspond to the OS data (if his previous drawing is decent then hopefully there will be an accurate building outline or something he can use).

Once that is done he can simply save the DWG and send it back to you. There should be no need to assign a co-ord system. You can then open that DWG in QGIS or Arc and everything should be in the right place.

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