I am importing GPS data into ArcInfo from a .csv file using Make XY Event Layer. I then convert this to a feature class in a File Geodatabase.

The coordinates have been collected using WGS84. When I input the Spatial Reference details I select Geographic Coordinate Systems > World > WGS 94.prj.

I then attempt to Project to GDA94 - specifying the Output Coordinate System to be Geographic Coordinate Systems > Australia and New Zealand > Geocentric Datum of Australia 1994.prj

It then requires a Geographic Transformation and only offers GDA_1994_To_WGS_1984 - I actually want the reverse.

The result is the points have exactly the same coordinates (to the 8th decimapl place) and positions. I believe there should be a small shift in coordinates if the projection was working correctly.

Any assistance would be greatly appreciated.

John

The coordinates have been collected using WGS84. When I input the Spatial Reference details I select Geographic Coordinate Systems > World > WGS 94.prj.

I then attempt to Project to GDA94 - specifying the Output Coordinate System to be Geographic Coordinate Systems > Australia and New Zealand > Geocentric Datum of Australia 1994.prj

It then requires a Geographic Transformation and only offers GDA_1994_To_WGS_1984 - I actually want the reverse.

The result is the points have exactly the same coordinates (to the 8th decimapl place) and positions. I believe there should be a small shift in coordinates if the projection was working correctly.

Any assistance would be greatly appreciated.

John

Pretty sure that the transformation is the same whether you're going GDA94 to WGS84 or back the other way.

ArcMap also reprojects on the fly, so you might have two layers in ArcMap and one is GDA94 and the other WGS84 and they will appear in the same location. GDA94 and WGS84 both use geographic coords (like -34.1234, 150,1234).

Not sure about whether GDA94 and WGS84 should have slightly different coords...