Create Custom Geographic Transformation (Data Management)

Summary

Creates a transformation definition for converting data between two geographic coordinate systems or datums. The output of this tool can be used as a transformation for any tool with a parameter that requires a geographic transformation.

Usage

• All custom geographic transformation files are saved with the .gtf extension and stored in the Esri\ArcGISPro\ArcToolbox\CustomTransformations folder in your application data folder.

  • In all Windows operating systems, the AppData folder is in %appdata% and the temp folder is in %temp%. Entering %appdata% in a command window returns the AppData folder location. Entering %temp% returns the temp folder location.
  • In UNIX systems, the tmp and application data folders are located in your home directory, under $TMP and $HOME, respectively. Typing /tmp in a terminal returns the location.

• Any geoprocessing tool that uses geographic transformations will inspect all custom transformations in the default storage location and present them as options in the transformation parameter's drop-down list. The transformations will also be available to the Geographic Transformations environment.

• You cannot edit custom transformation files. They are binary files that store version and string length information that may be corrupted if modified. To update a transformation file, create a new custom geographic transformation and overwrite the existing file.

• Transformation methods are divided into two groups: equation based and file based. Equation-based methods do not need external information. File-based methods require a file or files that are stored on disk to calculate the coordinate offset values. The files are similar to rasters— with regularly spaced points—and an offset for a location is calculated by using an interpolation method and values from surrounding points.

• Files must be placed in one of following locations:

  • If ArcGIS Coordinate Systems Data is installed on a per-machine (for everyone) basis, copy the file or files to the C:\Program Files (x86)\ArcGIS\CoordinateSystemsData\pedata\Geographic folder.
  • If ArcGIS Coordinate Systems Data is installed on a per-user basis, copy the file or files to the C:\Users\username\AppData\Local\Programs\ArcGIS\CoordinateSystemsData\pedata\Geographic folder.
  • If ArcGIS Coordinate Systems Data is not installed, copy the file or files to the ArcGIS AllSource pedata folder at C:\Program Files\ArcGIS\Pro\Resources\pedata if ArcGIS AllSource is installed on a per-machine (for everyone) basis.
  • If ArcGIS AllSource is installed on a per-user basis, copy the file or files to the ArcGIS AllSource pedate folder at C:\Users\username\AppData\Local\Programs\ArcGIS\Pro\Resources\pedata.

  If you didn't use the default installation locations for ArcGIS AllSource or the ArcGIS Coordinate Systems Data, copy the files to the equivalent pedata folder. If these locations are not available because of permission restrictions or are hidden, ask your system administrator to help you.

Parameters

Dialog

Label	Explanation	Data Type
Geographic Transformation Name	The name of the custom transformation definition.	String
Input Geographic Coordinate System	The starting geographic coordinate system. Provide a well known ID (WKID) or use the Select Coordinate System button to select a coordinate system.	Coordinate System
Output Geographic Coordinate System	The final geographic coordinate system. Provide a well known ID (WKID) or use the Select Coordinate System button to select a coordinate system.	Coordinate System
Custom Geographic Transformation	The custom transformation method. A list of the methods and parameters is available in the Geographic and Vertical Transformations pdf. From the drop-down list, choose the transformation method that will be used to transform the data from the input geographic coordinate system to the output geographic coordinate system. Once chosen, additional options will appear below the transformation method.	String

Derived Output

Label	Explanation	Data Type
Output Transformation	The output transformation.	Value Table

Python

arcpy.management.CreateCustomGeoTransformation(geot_name, in_coor_system, out_coor_system, custom_geot)

Name	Explanation	Data Type
geot_name	The name of the custom transformation definition.	String
in_coor_system	The starting geographic coordinate system.	Coordinate System
out_coor_system	The final geographic coordinate system.	Coordinate System
custom_geot	The custom transformation method. A list of the methods and parameters is available in the Geographic and Vertical Transformations pdf. Set the METHOD and PARAMETER values wrapped in a string for custom transformation GEOGTRAN. Set the name of the method from the available methods of Geocentric_Translation, Molodensky, Molodensky_Abridged, Position_Vector, Coordinate_Frame, Molodensky_Badekas, NADCON, HARN, NTV2, Longitude_Rotation, Unit_Change, and Geographic_2D_Offset. Each method has a set of parameters. You can edit the option values by entering text next to the name of the parameter within the whole string representation of the custom geographic transformation. See examples in the Python sample below.	String

Derived Output

Name	Explanation	Data Type
out_transformation	The output transformation.	Value Table

Code sample

CreateCustomGeoTransformation example (stand-alone script)

The following stand-alone script uses the CreateCustomGeoTransformation function to create a custom transformation.

# Name: CreateCustomGeographicTransformation.py
# Description: Create a custom geographic transformation in the default directory.

# import system modules
import arcpy

# set the variables
geoTransfmName = "cgt_geocentric2"

# create a spatial reference object for GCS_Tokyo
inGCS = arcpy.SpatialReference("Tokyo")

# create a spatial reference object for GCS_WGS_1984
outGCS = arcpy.SpatialReference("WGS 1984")

customGeoTransfm = "GEOGTRAN[METHOD['Geocentric_Translation'],PARAMETER['X_Axis_Translation',''],PARAMETER['Y_Axis_Translation',''],PARAMETER['Z_Axis_Translation','']]"

arcpy.management.CreateCustomGeoTransformation(geoTransfmName, inGCS, outGCS, customGeoTransfm)

Environments

This tool does not use any geoprocessing environments.