Hello, every one. Here comes a problem I meet, when I want transfer coordinate from GCS_WGS_1984 to WGS84. The "geographic transformation (optional)" has so many option, which one I can select? Are there someone meet the problem like me? [ATTACH=CONFIG]31985[/ATTACH]
If your goal is to get your data in GoogleEarth, you can just Export to KML from the Conversion tools. It will take care of the coordinate conversion for you (we commonly export from a local coordinate system). The coordinate translation will cause some shifting of data based on the coordinate translation, but considering GoogleEarth is used for visualization instead of analysis, it probably won't be a problem.
The transformation parameter is 'optional' because it is unnecessary when the input and output geographic coordinate reference systems are the same. When they are different, the parameter becomes mandatory in the Project Tool.
If the output coordinate system is WGS 84 (latitude-longitude), you don't need to project it. If the needs to have a different version of WGS 1984 (name is different), use the Define Projection tool instead. That will update the 'metadata' and not change the coordinate values.
Another method is add the data to ArcMap. Set the data frame's coordinate system to what you want to use. Right-click the layer in the table of contents and select data, export data. In the dialog, choose to use the data frame's coordinate system.