ListTransformations

Summary

Returns a list of valid transformation methods. An extent can be used to narrow the list of valid transformation methods for a specific geographic area.

The most appropriate transformation is usually the first one in the returned list. The list is sorted by amount of overlap of the data versus the areas of use of the transformations. If two or more transformations have the same amount of overlap with the data, the transformation accuracy values are used as a secondary sort parameter.

For a list of transformations and their area of use, see the following knowledge base article: How To: Select the correct geographic (datum) transformation when projecting between datums.

Syntax

ListTransformations (from_sr, to_sr, {extent})

Parameter	Explanation	Data Type
from_sr	The starting geographic coordinate system. This can be specified with a SpatialReference object, the name of the spatial reference, or a path to a projection file (.prj).	SpatialReference
to_sr	The final geographic coordinate system. This can be specified with a SpatialReference object, the name of the spatial reference, or a path to a projection file (.prj).	SpatialReference
extent	Only transformations that span the entire extent will be returned. The extent needs to be specified in coordinates from the from_sr. When working with data, the extent on a Describe object can be used.	Extent

Return Value

Data Type	Explanation
String	A list of valid transformation methods.

Code sample

ListTransformations example

Use ListTransformations to identify valid transformations for projecting from one coordinate system to another.

import arcpy

from_sr = arcpy.SpatialReference('WGS 1984')
to_sr = arcpy.SpatialReference('NAD 1927 StatePlane California VI FIPS 0406')

extent = arcpy.Extent(-178.217598182, 18.9217863640001,
                      -66.969270909, 71.4062354550001)
transformations = arcpy.ListTransformations(from_sr, to_sr, extent)