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I am located in Canada and use a lot of historical data which is in NAD83 original. NAD83 original was found to be flawed, and in Canada was updated to NAD83(CSRS). I find QGIS projects CSRS quite accurately, but NAD83 is always an issue when using with data in other CRS. I use NRCan's NTv2 tool to transform my NAD83 original data into CSRS right now and that works well, but it takes time and it would be great to be able to do this right in QGIS automatically.

I know you can integrate a NTv2 transformation into QGIS, but I am not sure how to apply it to my particular situation. Where I am confused is that NAD83 original (in particular UTM zone 21 EPSG: 26921) is already in QGIS, so I dont understand how to use the custom projection feature in this use case.

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  • have you tried gis.stackexchange.com/questions/298465/… ?
    – Mapperz ♦
    Commented Jan 18, 2022 at 21:10
  • I did, I just am not sure what to put in the parameters box. Should I put in the parameters of the CRS that I find is inaccurate and requires the transformation (NAD83), or the parameters of the CRS (CSRS) that works well in Q and is the destination CRS of the transformation?
    – Ian
    Commented Jan 19, 2022 at 13:43
  • "...NAD83 is always an issue when using with data in other CRS." "...the parameters of the CRS that I find is inaccurate..." Can you elaborate? Maybe some examples of what isn't lining up? Are you using the Province-specific GSB's or the Canada-wide Datum?
    – Pointdump
    Commented Jan 19, 2022 at 16:08
  • I am using the NLCSRSV4.GSB for Newfoundland and Labrador for my NTv2 transformations. Newfoundland and Labrador has a published monument network online arcgis.com/apps/webappviewer/… and each monument has coordinates in both CSRS and NAD83 original. If I download the monuments as a CSV, and add them into a project as two different layers, one using the CSRS CRS, the other the NAD83, the points do not align. They are usually about 1 meter out
    – Ian
    Commented Jan 21, 2022 at 12:55

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