Adding X, Y data to Attribute Table

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11-23-2010 12:50 PM
SimonKettle
Regular Contributor
I am and have successfully added X,Y data using the built in ArcGIS toolbox 'data management tools' > 'Features' to add X, Y data to the attribute table from point data. However this has caused a problem, for I have been using the data to build up a model in Petrel, hence exporting the X,Y coordinates via a text file and my collegue dosen't understand why the coordinates have negative values. I suggested this is due to them being south of the 'equator' and west of the central meridian on the projection system I have been using.

Is there a way of exporting the X, Y values in Decimal Degrees rather than meters (which I think it exports the data as)? I have a screen shot below showing the negative attributes in the Y coloumn. The values are quite large intergers suggesting meters as the output type.
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MelitaKennedy
Esri Notable Contributor
I am and have successfully added X,Y data using the built in ArcGIS toolbox 'data management tools' > 'Features' to add X, Y data to the attribute table from point data. However this has caused a problem, for I have been using the data to build up a model in Petrel, hence exporting the X,Y coordinates via a text file and my collegue dosen't understand why the coordinates have negative values. I suggested this is due to them being south of the 'equator' and west of the central meridian on the projection system I have been using.

Is there a way of exporting the X, Y values in Decimal Degrees rather than meters (which I think it exports the data as)? I have a screen shot below showing the negative attributes in the Y coloumn. The values are quite large intergers suggesting meters as the output type.


Hi Simon,

If the data does have a defined coordinate system, you can use the calculate geometry option on the attribute table in ArcMap. First set the data frame's coordinate system to what you want the values to be. The calculate geometry tool will then let you choose to use the data frame's (or the data's coordinate system.

For some reason, I could only access a thumbnail of your attachment so couldn't see what the coordinate values were. Data that's in a geographic coordinate system will have negative X/easting values if the data is west of the prime meridian (usually Greenwich) or negative Y/northing values if south of the equator, and values will be relatively small.

Data in a projected coordinate system (PCS) would normally have negative values to the west and south of the longitude/latitude of origin. That could be the central meridian, or have other names. However, most PCS have false easting or false northing values applied to make sure most of the data has postive coordinate values. In fact, seeing negative numbers with data in a PCS can be a sign that the data is outside the normal usage.

Melita
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SimonKettle
Regular Contributor
Sorry about the attachment I must have made it too small.

The original XY plots were in meters and I used the calculate geometry tool to change this to DD. This worked just fine, but with some negative values. These values were commonly negative to -2 or -3 DD, these points fall outside of the UTM grid I was told to put the points into (37N) so are an eventuality I figure.

Thank you very much for your help.
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MelitaKennedy
Esri Notable Contributor
Sorry about the attachment I must have made it too small.

The original XY plots were in meters and I used the calculate geometry tool to change this to DD. This worked just fine, but with some negative values. These values were commonly negative to -2 or -3 DD, these points fall outside of the UTM grid I was told to put the points into (37N) so are an eventuality I figure.

Thank you very much for your help.


Oh, I see. I bet the negative DD values were in the latitude/Y field. Thanks!
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SimonKettle
Regular Contributor
Oh, I see. I bet the negative DD values were in the latitude/Y field. Thanks!


Yep they were. This all worked out successfully, now to make the maps look beautiful...
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