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Having followed manual instructions I am experiencing problems joining data to a map. What I have is a UK Districts shapefile and imported data with my coordinate data in it.

This coordinate data I produced in excel by assigning centroids to each district. On advice I imported my excel file as a Personal geodatabase(.mdb) instead because apparently(ArcGis Join Data CSV Problem) ARCGIS treats this better but I still cannot fully merge layers.

The coordinates to 'map' onto my map correctly - see image - but the two layers are not joined. I have the error that I need to define a projection. I try to do this through the ARC Toolbox but it still says unknown coordinate system in properties. I then add Join/Relate from the properties window but get another error message.

What Can I do to diagnose the problem here? I've been stuck for so long!

enter image description here

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  • When you import your table into the ArcMap and display the XY coordinates, you should have set the CRS then.
    – MacroZED
    Aug 9 '16 at 13:56
  • Thanks @MacroZED - when I first go to display XY data and specify this it says 'Table specified does not have an object ID field so I won't be able to define Relates. Coudl this be the problem?
    – Henry Dark
    Aug 9 '16 at 13:59
  • No it shouldnt be. I would try using your excel spreadsheet (.xls) as the source of your Lat/Long data. Go to "Add data" > Excel Spreadsheet. Once its been added to your map window, right click the spreadsheet and "Display X/Y data". Select your lat longs, and the reference system. Once the temporary point data is displayed, make sure you finalise it by exporting as shapefile or feature class in GDB. Try that.
    – MacroZED
    Aug 9 '16 at 14:09
  • No, unfortunately no luck. Even R has never caused me this many difficulties and I took care to make sure the dataset was properly cleaned, labelled and presented.
    – Henry Dark
    Aug 9 '16 at 15:16
  • Add a screenshot of your excel spreadsheet please? Are your coordinates in decimal degrees?
    – MacroZED
    Aug 9 '16 at 15:19
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The coordinate system within the spreadsheet is in British National Grid. These will need to be converted into Decimal Degrees before you can import them into ArcMap. Use http://gridreferencefinder.com/batchConvert/batchConvert.php to batch convert.

Once you have the new coordinates, import your excel spreadsheet (.xls) into ArcMap. Go to "Add data" > Excel Spreadsheet. Once its been added to your map window, right click the spreadsheet and "Display X/Y data". Select your lat longs, and the reference system, usually WGS84. Once the temporary point data is displayed, make sure you finalise it by exporting as shapefile or feature class in GDB.

If you other shapefile is using BNG, you can use the "Project" tool to convert these into WGS84.

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  • I just read my shapefile into R to check its coordinate type and saw that its in just one column and basically two combined strings (please see image above). How is it even able to read that at all as a meaningful shape and any ideas how to rectify? Thanks, super helpful.
    – Henry Dark
    Aug 9 '16 at 16:25
  • Im not sure what you mean. It might just be a text formatting issue. However this is a different question all together, so please mark this as complete and ask another question on the stack exchange.
    – MacroZED
    Aug 10 '16 at 8:40

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