How To: Change the default transformation used between two datums


ArcPad stores an internal list of methods and parameters used for transforming coordinates between two datums. When more than one transformation method or set of parameters exists for two datums, ArcPad, by default, uses the first match it finds in this list. The default transformation method ArcPad uses can be overridden by modifying the file defaulttransforms.dbf in ArcPad's System folder.


  1. Locate the file defaulttransforms.dbf in ArcPad's System folder (default is C:\Program Files\ArcPad 7.0\System).
  2. In a DBF editor (for example FoxPro or Excel), add a new entry and enter the Transform, Datum_1, and Datum_2 values.

    Transform: The name of the transformation
    Datum_1: The first datum
    Datum_2: The second datum

    Datum transformations work in either direction.
    For example, the transformation listed as NAD_1927_to_NAD_1983_NADCON will transform from from NAD 1983 to NAD 1927, as well as from NAD 1927 to NAD 1983.

  3. Save the updated defaulttransforms.dbf. This file must be saved in ArcPad's System folder and ArcPad must be restarted for the specified defaults to be applied.

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