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I've built various QGIS projects that use Canadian UTM and MTM CRS. They worked just fine in QGIS versions through 3.8 (based on proj4 and ?proj5).

In QGIS windows version 3.10.0-3, things got borked with the transition to proj6. QGIS version 3.10.1 seems to have largely fixed that, after I manually also installed proj-datumgrid-north-america in OSGeo4W. My maps display fine again, with CRS conversion on the fly, without pop-up errors.

However, my QGIS message log silently displays the following, with the so-called critical errors repeating during any map redraws. (EPSG:2951 is my project CRS. It's NAD83 (CSRS) MTM zone 9.)

2019-12-11T10:39:56     CRITICAL    Cannot normalize transform between EPSG:2951 and EPSG:4326
2019-12-11T10:40:04     CRITICAL    Cannot normalize transform between EPSG:4326 and EPSG:2951
2019-12-11T10:40:04     CRITICAL    Cannot normalize transform between EPSG:3857 and EPSG:2951
2019-12-11T10:40:04     CRITICAL    Cannot normalize transform between EPSG:26918 and EPSG:2951

Now (3.10.1), the maps look normal, but I'm still surprised at critical errors, even if silent ones. Should I be worried, and if so what should I do?

  • You shouldn't need a grid file to convert between CSRS and WGS84. EPSG has 2 transformations, both self-contained. There isn't one between NAD83 and NAD83 (CSRS) (26918 and 2951). I with I had an answer. – mkennedy Dec 11 '19 at 18:34
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Solved. It was a bug, which has Nyall Dawson has fixed after I raised it as an issue. The fix is present in version 3.11.0-40+.

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