Hi Seth, Thanks for taking a look. I've had a look at some of the existing test cases and managed to make some tests which show the issue more clearly. I can open an issue and link to a branch with these updated tests, I'll try to do this later today or tomorrow.
I've written an algorithm in python which we will use in the mean time to pre-calculate the corrected angles. I'm more than happy to share that code if someone would like to try to port it to mapserver. I can also take a look if I have time, but have to admit my C++ isn't very up to scratch. To avoid taking a lot of time calculating on the fly it would also be smart to cache the point-wise rotation angle used to convert between different projections, and I'm unsure how this would be handled in mapserver. Thanks, Alistair On Sat, 11 Oct 2025 at 12:01, Seth G <[email protected]> wrote: > Hi Alistair, > > The Mapfile and requests look fine to me, so this is likely an oversight > in the implementation. > It would be good to get this logged as an issue, ideally with a > recreatable test case at https://github.com/MapServer/MapServer/issues. > > Seth > > -- > web:https://geographika.net & https://mapserverstudio.net > mastodon: @[email protected] > > On Mon, Oct 6, 2025, at 12:16 PM, Alistair Everett wrote: > > Hi Seth, > > Thanks for your reply, we're just reprojecting the data. I'll take a > closer look at the test case too, since it seems like that should be > reprojecting from stereographic to geographic. I should also be able to > pull together some test data in the next few days too, I can open an issue > with it when I've put it together. > > Here are a couple of example requests: > > One in EPSG:4326 > > localhost:8000/wms?REQUEST=GetMap&SERVICE=WMS&VERSION=1.3.0&FORMAT=image%2Fpng&STYLES=wind_barb&TRANSPARENT=TRUE&TIME=2025-10-06T07%3A00%3A00Z&DIM_PRESSURE=50.0&DIM_REFERENCE_TIME=2025-10-06T03%3A00%3A00Z&LAYERS=wind_pl_vector_meps_det_vdiv_2_5km_calculations&WIDTH=1304&HEIGHT=1504&CRS=EPSG%3A3857&BBOX=-2460529.2703191666%2C4596419.518351211%2C6809846.057963322%2C15288631.55342549 > > https://pasteboard.co/jI1eMKaj3PT1.png > > This is one in EPSG:3411: > > localhost:8000/wms?REQUEST=GetMap&SERVICE=WMS&VERSION=1.3.0&FORMAT=image%2Fpng&STYLES=wind_barb&TRANSPARENT=TRUE&TIME=2025-10-06T16%3A00%3A00Z&DIM_PRESSURE=50.0&DIM_REFERENCE_TIME=2025-10-06T03%3A00%3A00Z&LAYERS=wind_pl_vector_meps_det_vdiv_2_5km_calculations&WIDTH=1438&HEIGHT=1504&CRS=EPSG%3A3411&BBOX=404935.5094684181%2C-3769428.4764078585%2C4977748.7994076125%2C1013263.5876175575 > > https://pasteboard.co/IHZjgXibtLyJ.png > > Thanks, > Alistair > > > On Sun, 5 Oct 2025 at 10:00, Seth G <[email protected]> wrote: > > > Hi Alistair, > > Could you give an example request (I presume it is WMS?)? Are you rotating > your map at all, or is it just the projection? > > There are some tests which reproject a UVRASTER LAYER at > https://github.com/MapServer/MapServer/blob/29e4ae81620a2c50201101c763df0b9d8d540b67/msautotest/wxs/wms_uvraster_map_reprojection.map > It sounds like an oversight, so if you are able to create a standalone > test case, it would be worth opening an issue. > > Seth > > -- > web:https://geographika.net & https://mapserverstudio.net > mastodon: @[email protected] > > On Fri, Oct 3, 2025, at 11:59 AM, Alistair Everett via MapServer-users > wrote: > > Hi all, > > I'm trying to use the UVRASTER connection to plot wind barbs. I noticed if > I request the layer in a different projection the location of the arrows > are reprojected but the angle, and presumably vector components, are not - > rather they remain in the same direction relative to my screen. It's a > little unclear from the documentation if this is the expected behaviour for > UVRASTER or not? I included a pasteboard link to a screenshot to show what > I mean, compare for example vectors in the corners of the data and you will > see they point in the same direction relative to my screen, rather than > being rotated to match the projection. > > If this is expected, does anyone have any suggested ways of working around > this? > > If this is not expected, does anyone have any ideas what I've done wrong? > I can provide some sample data if someone wants to try to reproduce. > > I'm using: MapServer version 8.4.0 PROJ version 9.4 GDAL version 3.11 > OUTPUT=PNG OUTPUT=JPEG SUPPORTS=PROJ SUPPORTS=AGG SUPPORTS=FREETYPE > SUPPORTS=CAIRO SUPPORTS=ICONV SUPPORTS=FRIBIDI SUPPORTS=WMS_SERVER > SUPPORTS=WMS_CLIENT SUPPORTS=WFS_SERVER SUPPORTS=WFS_CLIENT > SUPPORTS=WCS_SERVER SUPPORTS=SOS_SERVER SUPPORTS=OGCAPI_SERVER > SUPPORTS=FASTCGI SUPPORTS=THREADS SUPPORTS=GEOS SUPPORTS=PBF INPUT=JPEG > INPUT=OGR INPUT=GDAL INPUT=SHAPEFILE INPUT=FLATGEOBUF > > Screenshot: https://pasteboard.co/WTgbexDmQaAe.png > > Example mapfile: https://pastebin.com/ibPc6gVK > > Thanks, > Alistair > > ----------------------------- > Dr Alistair Everett > Senioringeniør / Senior Software Engineer > Avdeling for Geoutvikling > > Phone: +47 939 68 985 > Email: [email protected] > > Meteorologisk Institutt, > Henrik Mohns plass 1, > 0313 Oslo > ----------------------------- > *Dr Alistair Everett* > Senioringeniør / Senior Software Engineer > Avdeling for Geoutvikling > > *Phone:* +47 939 68 985 > *Email:* [email protected] <[email protected]> > > *Meteorologisk Institutt*, > Henrik Mohns plass 1, > 0313 Oslo > > _______________________________________________ > MapServer-users mailing list > [email protected] > https://lists.osgeo.org/mailman/listinfo/mapserver-users > > > >
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