Transform (Coverage)


Moves all features in a coverage based on a set of from and to control points.

Learn more about how Transform works


Transform illustration



Transform_arc (in_cover, out_cover, {transform_type})
ParameterExplanationData Type

The coverage whose coordinates are to be transformed.


The name of an existing coverage containing destination tics. The features from the input coverage will be transformed into this coverage.


The type of coordinate transformation to be performed:

  • AFFINEPerforms an affine transformation. At least three tics are required to define this transformation. If only two tics are matched, a similarity transformation will be applied. The AFFINE equations use six parameters.
  • PROJECTIVEPerforms a projective transformation. This requires a minimum of four tics to define the transformation. The projective transformation is only used to transform coordinates digitized directly off high-altitude aerial photography or aerial photographs of relatively flat terrain, assuming there is no systematic distortion in the air photos. PROJECTIVE uses eight parameters.
  • SIMILARITYPerforms a similarity transformation. At least two tics are necessary for this transformation. This transformation is also known as a Helmert, orthogonal, two-dimensional linear conformal, or four-parameter transformation.

Code Sample

The following stand-alone script demonstrates how to use the Transform tool on a digitized coverage. First it creates an empy output coverage based on a template coverage. The template has tics and a defined projection. The empty output coverage is named roads. Then it transforms the digitized road features into the empty roads coverage.

# Name:
# Description: Transforms digitized road features into a new output coverage
# Requirements: ArcInfo Workstation
# Author: ESRI

# Import system modules
import arcpy
from arcpy import env

# Set environment settings
env.workspace = "C:/data"

# Set local variables
inCover = "roads_dig"
outCover = "C:/output/roads"
transformType = "AFFINE"

# Create the empty output coverage
arcpy.Create_arc(outCover, "citylim")

# Execute Transform
arcpy.Transform_arc(inCover, outCover, transformType)

# Print the RMS error
print arcpy.GetMessage(4)


Related Topics

Licensing Information

ArcView: No
ArcEditor: No
ArcInfo: Requires ArcInfo Workstation installed

Published 6/8/2010