[mapserver-dev] UVRaster RLatLon GRIB2 data not working properly on Mapserver

[Laframboise,Felix (ECCC)]

Hi,

I am currently using GDAL 3.1.3 and Mapserver 7.6.2 on a Ubuntu machine. I created a UVRaster layer with a style using arrow symbols. The source data is GRIB2 files using a Rotated Latitude-Longitude grid data (RLatLon).

When I tested the layer, I noticed that it does not output correctly. Sometimes, no image outputs, and sometimes all the arrows/data seem to be clustered somewhere on the extent. The expected extent should be the one of North America (approximatively [-154, 26, -42, 70] in the [min_x, min_y, max_x, max_y] format), where all the arrows are spread out on this extent.

Following this output, I did investigate the issue, and the mapfile is working fine as I tested it with other data that is not using a RLatLon grid.

I created a test case to show you the issue here:

·       Sample mapfile: https://pastebin.com/h06AsJzz

·       Sample VRT: https://pastebin.com/ERViMRpR

·       2 UV GRIB2 files (available here: https://dd.weather.gc.ca/model_hrdps/continental/2.5km/grib2/00/000/ ) for the source data (using following patterns) :

o    *_MSC_HRDPS_UGRD_AGL-40m_RLatLon0.0225_*.grib2

o   *_MSC_HRDPS_VGRD_AGL-40m_RLatLon0.0225_*.grib2

·       Output image when arrows are clustered: https://pasteboard.co/WMoun7bhLZSl.png

We serve the mapfiles using Python mapscript but I tested the mapfiles with a mapserv command and got the same result.


Do you have an idea what could be the issue and how to solve it? RLatLon data is working fine with Mapserver, but it seems to only affect UVraster layers.

Thanks a lot in advance for your answer(s)!


Félix Laframboise
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