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 Canadian Natural Resources website.
To convert NAD27 to NAD83 using NTv2, the first step is to download the conversion file.
- Download the ZIP file from the Natural Resources Canada webpage (you will need to sign in to access the page). Additional information about this NTv2 grid shift file can be found on their site here.
- Extract the file NTV2_0.GSB to the Surfer installation directory (e.g. C:\Program Files\Golden Software\Surfer).
Now you can use the NAD 1927 - Canada (NTV2) datum as the source coordinate system in Surfer when converting to another system with the NAD83 datum. For example:
- Select a map layer in the Contents window (e.g. Contours).
- In the Properties window, click the Coordinate System tab and click the Set button.
- In the Assign Coordinate System dialog, select the source coordinate system for the layer (e.g. Predefined | UTM | North America | North America NAD27 UTM zone 11N)
- Click Modify.
- In the Define Coordinate System dialog, change the Datum to NAD 1927 – Canada (NTV2).
- Click OK, then OK again. The source coordinate system is specified to use the NTv2 datum transformation.
- To convert the map to NAD83, select Map in the Contents window.
- In the Properties window, click the Coordinate System tab and click the Change button.
- In the Assign Coordinate System dialog, select the NAD83 coordinate system you want the map to be displayed in (e.g. Predefined | UTM | North America | North America NAD83 UTM zone 12N).
- Click OK and the map is converted.
Updated October 31, 2018