To Change the Vertical Datum of a GCS
In the Geographic Coordinate System dialog, select the From Library icon.
The Select Geographic Coordinate System dialog opens.
- On the Library tab, expand the folders as needed to locate a GCS that uses a datum of NAD27, NAD83, HPGN, or their equivalent.
- Click OK.
- In the Geographic Coordinate System dialog, click Details. The Geographic Coordinate System Properties dialog opens.
- On the Coordinate System Modifiers section, in the Vertical Datum drop-down list, change the vertical datum to National Geodetic Vertical Datum of 1929 or North American Vertical Datum of 1988.
If Reproject Elevation to "Yes" in the Reprojection Settings dialog, the Geographic Coordinate Systems Changed dialog opens.
- Select the appropriate option for your data, to either reproject or not reproject the data.