InstallNTv2

In Canada, to use the best available geographic transformation method for converting from Nad27 to Nad83 one must acquire grid shift files (gsb) from Natural Resources Canada. The files are free of charge, but redistribution is restricted.

Acquire the grid shift files, choose one of:

• Fill out the form for NTv2 download on ESRI Canada website (download is immediate).
• Go to NRCan's website and request download URL for the NTv2 files (it will be emailed).

For ArcGIS Desktop, copy ntv2_0.gsb to C: \path to \ArcGIS\pedata\ntv2\canada. Create the canada folder if it does not exist. (ref)

For ArcInfo Workstation, rename $archome\datum\cnt.* cnt_v1.*, and copy cnt.def and cnt.dat from the source archive in their place.

For GDAL/OGR copy ntv2_0.gsb to .../share/proj (e.g. c:\osg4w\share\proj), and rename to lower case. (ref)