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How To: TRANSFORM a coverage in ArcCAD

Summary

TRANSFORM is used to change the coordinates of a coverage using an affine or projective function based on control points (tics). TRANSFORM is often used to convert themes created in inches or centimeteres into real-world units represented on a map.

Procedure

Follow these steps in order to transform a coverage:

  1. Define a tic theme that points to the coverage (GIS data set).

    Code:
    DEFTHM

    [O-Image] DEFTHM
  2. Copy this theme to another theme.

    Code:
    Command:COPYTHM
    Input data set (?/MYTIC) Enter or mytic
    Output theme (?): newtic
    Theme NEWTIC is not defined.
    Defining NEWTIC...

  3. Make appropriate edits to newtic.dbf. Substitute new coordinate values for
    the new coordinate system.

    Code:
    Command: modrec
    Theme name (?/<NEWTIC>):
    Updating NEWTIC userid...

    Note:
    You now have two tic themes, one is pointing to the original GIS data set(MYTIC)and the other is within the empty directory NEWTIC.

    [O-Image] MODREC-WBROWSE
  4. Transform the coverage.

    Code:
    Command: transform
    Input theme (?/<NEWTIC>): mytic
    Output theme (?): newtic
    Transform method (Projective/<Affine>):Affine
    {Note}Use the Projective transformation option ONLY if the features of the input theme were digitized directly from aerial photographs. The accuracy will be defendant on the surface terrain


    Note:
    For additional information about the TRANSFORM function see the ArcCAD Command Reference book.