CSRS to NAD83 via Grid Files

CSRS (Canadian Spatial Reference System) is the Canadian equivalent to the U.S.'s HARN; that is, a very accurate rework of NAD83 using GPS technology. Like the US HARN, the shifts are in the range of 1 to 2 feet (40 centimeters).

This conversion technique is implemented by a series of datum shift grid files of the Canadian National Transformation format. Unlike other implementations by Canadians, however, there are multiple overlapping files involved so this situation is managed by the Geodetic Data Catalog feature. In this case, the name of the data catalog file is Nad83ToCsrs.gdc. Refer to this file for more information.

You can use the fallback feature of the Geodetic Data Catalog to specify how data points outside the coverage of existing data files are to be handled. Since the shift produced by this transformation is relatively small (e.g., 1 or 2 feet), this fallback feature is rarely used in this case.

Again, the data files are being generated on a province-by-province basis. The individual files may, or may not, be in the public domain. You may need to acquire the appropriate data files yourself in order to use the transformation.