How to Convert from NAD27 to NAD83 Using NTv2

NTv2 is the Canadian government's officially sanctioned method of converting Canadian map data from the old NAD27 datum to the NAD83 datum.  If you are converting from Lat/Long WGS84 (or any coordinate system with a datum other than NAD27) to NAD83, you will not need to use NTv2.  If you are converting data with a datum of NAD83 back to NAD27, you will not need to use NTv2. Again, this is only a method of converting data from the NAD27 datum to the NAD83 datum.

 

To perform the conversion, you do need an additional grid shift file in the Surfer installation directory. Golden Software cannot supply this file, but you can download it from the Natural Resources Canada website.

 

To convert NAD27 to NAD83 using NTv2, the first step is to download the conversion file.

  1. Download the ZIP file from the Natural Resources Canada webpage. You can find more information about this NTv2 grid shift file from their site.  

  2. Extract the file NTV2_0.GSB to the Voxler installation directory (by default this is C:\Program Files\Golden Software\Voxler 4).

 

Now you can use the NAD 1927 - Canada (NTV2) datum as the source coordinate system in Voxler when converting to another system with the NAD83 datum. For example:

  1. Click the Data | Assign Coordinate System command. The Assign Coordinate System dialog opens.

  2. Select the coordinate system for the data (e.g. Predefined | UTM | North America | North America NAD27 UTM zone 12N)

  3. Click Modify.

  4. Change the datum to NAD 1927 – Canada (NTV2).

  5. Click OK, then OK again. The souce coordinate system is specified to use the NTv2 datum transformation.

  6. To convert the map to NAD83, click the Data | New Projected Coordinates command.

  7. Click the next to the Target Coordinate System in the New Projected Coordinates dialog.

  8. Select the NAD83 coordinate system for the new projected coordinates (e.g. Predefined | UTM | North America | North America NAD83 UTM zone 12N).

  9. Specify the columns for the new coordinates.

  10. Click OK and the new projected coordinates are added to the worksheet.

 

 

See Also

Datums