Canadian Velocity Grid

The Canadian Velocity Grid for is an NTv2 grid shift file with 3D velocity data that accounts for motion of the crust over time. This format supports transformation between different Epochs of NAD83(CSRS) to account for the tectonic shift using the velocity field determined from active control stations.

The existing instance in the GeoCalc datasource is from NAD83 (CSRS) to NAD83 (CSRS) with the name: "National Epoch Transformation (NET) v6.0"

Support for the Canadian Velocity Grid was added in Geographic Calculator 2016 sp2, and this datasource object is not supported in earlier versions of the application.

"The National Epoch Transformation (NET) v6.0 propagates coordinates to and from NAD83 (CSRS) and the ITRF realizations by applying the Canadian GNSS velocity grid (CVG) v6.0 to the coordinates.

Since the NUVEL 1-A model has no vertical component and does not account for some regional crustal motion occurring within the plate and along its margins, NAD83 coordinates of a point do not remain constant over time. Provincial and federal survey agencies published their NAD83 (CSRS) coordinates based on realizations of NAD83 (CSRS) dated to specific NAD83 (CSRS) epochs (some 1997, others 2002). To ensure the coordinates confirm with the province's published coordinates they must relate to the same epoch."

-Natural Resources Canada

For more information see

https://www.nrcan.gc.ca/earth-sciences/geomatics/geodetic-reference-systems/9052#reference