I have shapefile (points) which I got from adding xy data in ArcMap from Excel table. I had Latitude/Longitude data. It is area of northern Australia.

For example (5 points):

Longitude 136.882 142.356 143.049 142.984 145.086

Latitude -12.249 -11.151 -12.659 -12.881 -15.135

What coordinate system should I define here and how?


2 Answers 2


I took your data and plotted it using WGS 1984 (in the ArcMap Coordinate System menu under Predined > Geographic Coordinate Systems > World > WGS 1984), which, in most cases is a good world standard to go with when you don't know the source coordinate system.

Australia data map


Use the Define Projection tool. You could define your shapefile as:

GCS_WGS_1984 Datum: D_WGS_1984


GCS_Australian_1984 Datum: D_Australian_1984

  • I did like you said, but when I try to import it into postgis database it gives me error: ERROR: Coordinate values are out of range [-180 -90, 180 90] for GEOGRAPHY type. Oct 20, 2011 at 16:40
  • 1
    It might help to, when you are initially importing the xy data, to define the coordinate system then.
    – Casey
    Oct 20, 2011 at 16:59
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    @againstflow, You should ask this as a seperate question since this question is different. I do not have experience with postgis. You can make reference to this question from your new question. Include a postgis tag in your new question.
    – artwork21
    Oct 20, 2011 at 17:02
  • Good point @Casey, before importing the XY event layer define your dataframe with the coordinate system you want to define your layer to.
    – artwork21
    Oct 20, 2011 at 17:03
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    @artwork21, the points are split between Northern Territory and Queensland. NT didn't update to AGD84 so those could be in AGD66. But I think it's more likely they're in GDA94 or WGS84.
    – mkennedy
    Oct 20, 2011 at 18:50

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