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 apply the directionality automatically. For example, if converting data from WGS84 to NAD 1927, you can choose the NAD_1927_to_WGS_1984_3 transformation, 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 supports composite transformation methods. The Project tool's transformation parameter and the arcpy.ListTransformations function provide valid transformations, including composite, between an input and an output. For example, ITRF_2000_To_WGS_1984 + ITRF_2000_To_NAD_1983_2011 can be used with this environment.
- If a projection requires multiple transformation methods, including composite, a tool will only use a single transformation from the environment. This is the case even if multiple transformation methods have been set. If a 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 a new coordinate system while buffering.
import arcpy # Set the workspace, outputCoordinateSystem and geographicTransformations # environments 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.analysis.Buffer("roads.shp", "roads_buffer.shp", "10 meters")