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How do I apply a geographic datum transformation in ArcGIS?
Procedure
- In ArcMap, go to View > Data Frame Properties dialog.
- Select the Coordinate System tab.
- Click the Transformations button at the bottom of the dialog (in older versions of the software, the Transformations button appears on the right.)
- Select one of the listed transformations.
Is NAD 1983 a geographic coordinate system?
The North American datum of 1983 (NAD 83) is the United States horizontal or geometric datum. Projected coordinate systems are based on geographic coordinates, which are in turn referenced to a datum. For example, State Plane coordinate systems can be referenced to either NAD83 and NAD27 geodetic datums.
Why do we need transformations in ArcGIS Pro?
This is necessary because the earth is actually a lumpy and slightly squashed sphere. The transformation is a calculation to convert the geographic coordinate system of the layers to match the geographic coordinate system of the map as the map draws so that everything is aligned. The data is not changed by a transformation.
When do you use a geographic transformation tool?
Tools that honor the Geographic Transformations environment will use the transformation methods when projecting data. Specify transformation methods that can be used to project data on the fly.
When to use a transformation in projection on the fly?
Transformations are one part of the process used by the Project tool and projection on the fly. If you are converting between different geographic coordinate systems (GCS), you need to use a transformation. In the example above, the map is in a projected coordinate system (PCS).
How does a geographic transformation change a datum?
Because geographic coordinate systems contain datums that are based on spheroids, a geographic transformation also changes the underlying spheroid. There are several methods, which have different levels of accuracy and ranges, for transforming between datums.