Import of NetCDF fails upon order of variables

[raphaeljolivet]

Qgis version : 3.18.0-Zürich

I struggled to import a NetCDF file as a mesh layer. I found that Qgis has strange and undocumented requirements for it.

The file in question :

• Is fully compliant with CF conventions (checked with CF-checker)
• Has one time dimension
• Has bidimensional lat, lon variables
• Has CRS / projection properly set for X and Y variables
• Has a single data variable "gis"
• Has been produced with "nkcs"

I found first that QGis requires the dimensions to be in a specific order : time, y, x. To my knowledge, this does not corresponds to any convention.

Then, if the variables are in alphabetical order (gis, lat, lon, time, x, y ) the file imports correctly :

• The layer is temporal
• The CRS is set
• Only one data variable "gis" is shown

However, if the same file has different order of variables (time, x, y, lat, lon, gis) then :

• The layer is not recognized as temporal
• The CRs is not set
• Two vairable are shown : lat, lon. gis is missing

I think this should be fixed and / or explained clearly in the documentation

I attach both files here : example-nc-files.zip

[roya0045]

@PeterPetrik Would you know if such issues are related to MDAL or QGIS-specific?

[PeterPetrik]

Hi, this is definitely MDAL issue please let discuss there.

[vcloarec]

@raphaeljolivet Indeed, it is a MDAL issue that will be fixed. Can you use your data for testing in MDAL?