RFE Grib_pi: Support Polar Stereographic Projection (for Canadians)

[rgleason]

A new Canadian user reports: Any idea why Canadian grib2 files aren't loadable in here? This must be a very simple answer. Sourced from: https://dd.weather.gc.ca/model_gem_regional

I have tried one of the files and it does not load.
Trying to get more info about the CA website and the source of the files.

I believe Grib_pi should be compatible.

[transmitterdan]

Rick,

Which file exactly? There seem to be many many files there.

I loaded this file: https://dd.weather.gc.ca/model_gem_regional/10km/grib2/00/008/CMC_reg_ABSV_ISBL_250_ps10km_2021093000_P008.grib2

It uses a projection type we don't support:

20	Polar Stereographic Projection (Can be North or South) (See Template 3.20)

We support template numbers: 0, 10, 30 & 40

from this specification: https://www.nco.ncep.noaa.gov/pmb/docs/grib2/grib2_doc/grib2_table3-1.shtml

[rgleason]

That is a huge help Dan. Thanks. I wonder if we could support Polar Sterographic? I suppost Didier could add that for our Canadian friends.

[bdbcat]

" wonder if we could support Polar Sterographic? "
That is a pretty big ask. OCPN supports Mercator projections, mainly, since this is the main navigational projection used worldwide. To support other projections, all the GRIB data would need to be re-projected (from Polar Sterographic to Mercator) before display. This is do-able, but is a non-trivial graphics exercise.
Dave

[rgleason]

Thanks Dave, that kind of answers the question, its a big ask, but I wonder if the world's new interest and awareness in the Poles might influence OpenCPN's charts at some point?

Should I close this now?

[bdbcat]

Yes, with grib_pi documentation update specifying exactly the projections supported.

[rgleason]

Added here

https://github.com/opencpn-manuals/plugins/blob/main/manual/plugins/modules/grib_weather/pages/grib_weather.adoc

Closing