NRCan provides helmert parameters which can be used to go from ITRF08 to NAD83CSRS. (https://webapp.geod.nrcan.gc.ca/geod/data-donnees/transformations.php?locale=en). I can put these into a proj4 string and convert a las file, and observe that the coordinates have been shifted.

However, there are other ways which I thought should work. For example PDAL can be used with a pipeline, or las2las can be used, by specifying the destination EPSG code. However, whenever I specify that I'm going from EPSG:32611 (WGS84 UTM zone 11) to EPSG:2955 (NAD83(CSRS) UTM zone 11), the output coordinates are just the same as the input coordinates.

This implies that the EPSG codes are either not properly defined (maybe using an incorrect CRSR epoch?), not recognized by software like pdal or las2las (yet they are not giving any warning or error), or something else is going on.

If those EPSG codes for NAD83(CSRS) do not actually represent NAD83(CSRS), then, if I use the helmert parameters to do the transform, how do I specify to future consumers what coordinate system the output is in, if no EPSG code exists that correctly represents it?

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