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. You can create a list of transformation methods the application can use, including custom transformations (those created using the Create Geographic Transformation tool) and system-supplied transformations (those out of the box).
When working with geographic transformations, if the direction is not indicated, geoprocessing tools will handle the directionality automatically. For example, if converting data from WGS 1984 to NAD 1927, you can choose a transformation called NAD_1927_to_WGS_1984_3, and the software will apply it correctly.
- You can include out-of-the-box transformation methods, those supplied by the application, those in the list, and custom transformation methods created using the Create Custom Geographic Transformation tool.
- Regardless of the number of transformations in the list, the application will only use those appropriate to the projection. All others will be ignored.
- The environment does not support composite transformation methods. If projecting the features requires multiple transformation methods, the application will not select multiple options from the environments list, regardless of whether the necessary transformation methods exist in the list. The same is true if your custom geographic transformation contains multiple methods. These will not be applied.
If the projection requires more than one transformation method, use the Project tool.
- Geographic Transformations—Create a list of transformation methods. This can include system-provided transformation methods as well as custom transformation methods created using the Create Custom Geographic Transformation tool.
arcpy.env.geographicTransformations = geographic_transformations
A semicolon-delimited string of transformation methods. This can include system-provided transformation methods as well as custom transformation methods created using the Create Custom Geographic Transformation tool.
Project data into new coordinate system while buffering.
# Set the workspace, outputCoordinateSystem and geographicTransformations
arcpy.env.workspace = "c:/data"
arcpy.env.outputCoordinateSystem = arcpy.SpatialReference("WGS 1984 UTM Zone 18N")
arcpy.env.geographicTransformations = "Arc_1950_To_WGS_1984_5; PSAD_1956_To_WGS_1984_6"
arcpy.Buffer_analysis("roads.shp", "roads_buffer.shp", "10 meters")