I have a few layers. The layers have been made by a different company. So

How do I combine them all together so that they have the same coordinate systems?

I already add the layers, right click < Data frame properties < coordinate system. And select a coordinate system. But it shows the same. The layers do not seem to overlap. (For example I pick a river layer at the same place, and I add a road layer also from the same place.) But they don't overlap.

Is it because the size of the layers are different?

Or is the coordinate system from map info is different from the beginning?


2 Answers 2


There is a page on Identifying an unknown coordinate system in the ArcGIS 10.1 Help.

If you need more help it would be useful to record in your Question what the Coordinate System tab of Layer Properties is reporting for the layer(s) causing you problems, as well as the Coordinate System of the Data Frame Properties those layers are being displayed in.

  • I follow the step that you give me. And now i'm stuck at layer properties < data source. And my hardware seem don't have 'add the file usstpln83.shp', and I search for the default folder C:\Program Files\ArcGIS\Desktop10.0, and there is no luck. Is it because my boss move the folder form Local Disk c: to the Desktop?
    – dark_kaoru
    Aug 10, 2012 at 3:12
  • 1
    I assume usstpln83.shp is one of your shapefiles but I would not recommend placing it in the default folder you mention. Wherever, it is located you should be able to browse to it - so try looking on the Desktop.
    – PolyGeo
    Aug 10, 2012 at 3:32
  • I check in there already and still have no luck. Actually there is no folder name Desktop 10 in my hardware. Only Dekstop tools, arcgis mobile, arcgis dekstop help and Phyton 2.6. And I also have prj file after convert from mapinfo. Just now I tried it again and this time the length between two layer is too far away but the size is almost similar now (which means that different from the first one I tried, the layer is overlap but one of the layer is so big). I think i need to do a lot more practice.
    – dark_kaoru
    Aug 10, 2012 at 3:52

I have a few pieces of advice in addition to the useful link PolyGeo provided.

  • Ensure you Define Projection (Data Management) only when you know the source projection.
  • Go to the data source to find the metadata, which will provide you critical coordinate/projection information.
  • Use Project (Data Management) when the projection is already correctly defined and you want to change to a different projection.
  • Try clearing the coordinate system in the Data Frame Properties > Coordinate System > Clear and then bring in your layers--this will ensure no previously saved coordinate system is interfering with your current coordinate system.

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