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CAD drawing has coordinates given but when this CAD file add to ArcGIS the coordinate showing is different. Why?

Actually the coordinates there shown is "Nahrawan 1967 utm 39". I use define projection and try to project it to WGS UTM 40N.It is still in the same position.

Cad cordinates

ArcGIS Coordinates

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    No, using Define Projection does not reproject data, it just corrupts the dataset metadata. The Project command changes projection. – Vince Nov 24 '19 at 5:34
  • Yes .I know. But using Define Projection i can set it to Nahrawan a projection.So if i change arcgis dataframe to Nahrawan it should come in exact location. but it fails. I reproject the cad file from defined nahrawan to wgs coordinate.Still its fails to come in exact location.The important part is when i reproject cad file to WGS 40N ,The exact coordinates corresponding to wgs 40N is shown in autocad map.but still it is in same location. – user147827 Nov 24 '19 at 6:08
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    for CAD in ArcGIS you need a wld file desktop.arcgis.com/en/arcmap/latest/manage-data/cad/… – Mapperz Nov 24 '19 at 17:17
  • According to my knowledge wld file are created when you georeference (Giving control points or actual coordinates) the file.But here the above indicated cad file is drawn by a coordinate system and when i pan through the cad file the coordinates are indicated below like the screenshot attached.If i use that coordinates it falls in actual position in GIS,but at the same time cad file is not fall in the actual location.I want to know why this happening ? – user147827 Nov 25 '19 at 3:23
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I used to do a lot of CAD to GIS conversions, and the CAD people were using ground coordinates as opposed to grid coordinates and there was usually a scale factor mentioned on the CAD drawing somewhere that I had to apply to convert the data. Perhaps you have a similar issue? You might also want to look at units as one may be in feet or inches, and the other in meters or some such thing.

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  • I didn't understand you fully.but i think may be you are correct. Could you tell me why this happening ? and how to rectify this ? – user147827 Nov 25 '19 at 16:06
  • CAD is a strange environment. As it is often used for construction, things are usually measured the way surveyors plot points on the ground. Which isn't necessarily the same way the GIS world measures coordinates. Usually they work from a local survey marker whose position is known, and then they have to calculate the local distortion of the map grid for the exact position they're looking at. A lot of that happens in the survey equipment, so when data comes into CAD, the draftperson may or may not be aware of the specifics in how the data was collected. – Colin Lang Nov 29 '19 at 19:04
  • Usually, the CAD drawing will specify the scale factor, or the translation, rotation and scale, based on the survey monument. If you can find that info on the CAD drawing, you can use it to create a custom projection in ArcGIS. – Colin Lang Nov 29 '19 at 19:06

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