Projecting an unreferenced NetCDF

The challenge with Netcdf is that it’s a very feature-rich, but also a very open format. This is why there are initiatives for standardizing how to structure the contents, such as the CF conventions. But these are optional.

I often find that the best way to get a full overview of a particular Netcdf file is to use the ncdump command line utility to dump the Netcdf header contents as text and inspecting the resulting dump. The reason is that there are possible constructs in the Netcdf header that aren’t always made visible in FME, e.g. grid mappings that can be used to map x/y cells to one or several geographic coordinate systems.

Failing that, I’m not sure you have many other options than either guessing or contacting the data source.

Given that it is New Zealand and you say it might be Lambert, I’d suggest trying the New Zealand Continental Shelf Lambert projection, EPSG:17964. Unfortunately it’s not supported in the Reprojector or ProjReprojector, so you would have to set up a manual transformation in the ProjReprojector

In my own experience, Netcdfs should (ideally ;-) contain the ground coordinates for each cell, but the way they do it can vary. If you manually reproject the raster, there’s a chance that you’ll deform the raster or introduce artefacts or weirdness at the boundaries. Depending on your use case, the consequence of this can vary from “I don’t care” to “the data is now unusable” and everything in between.

Therefore my recommendation would be to first check the “ncdump” for ground coordinates before going that route.

Thanks for the replies!
So each NetCDF file has a few features, of which ‘lat’ and ‘lon’ are present, plus the actual radar value i need ‘qpe_radar_adjusted’. See below. So i can combine these into a single raster to get 3 bands (lat, lon and qpe) - but when i try to project into lat/lon (as the name suggests) - its still being funky!