uvraster not rendered correctly

[kaiwirt]

Expected behavior and actual behavior.

Following the example from https://mapserver.org/input/vector/vector_field.html to visualize data from a GRIB file, the data is only rendered correctly, if the Bounding Box extends over the globe.

OK

The following request (See Image 1) works:
http:///mapserv?MAP=/config/maps.map&service=WMS&version=1.1.1&request=GetMap&layers=uv&SRS=EPSG:4326&BBOX=-180,-90,180,90&WIDTH=1000&HEIGHT=800&format=image/png&STYLES=

Not ok

The same request with longitude set to 179 doesn't (See Image 2)
http:///mapserv?MAP=/config/maps.map&service=WMS&version=1.1.1&request=GetMap&layers=uv&SRS=EPSG:4326&BBOX=-180,-90,179,90&WIDTH=1000&HEIGHT=800&format=image/png&STYLES=

OK

If the latitude is then set to 91 the data is rendered correctly again (See Image 3)
http:///mapserv?MAP=/config/maps.map&service=WMS&version=1.1.1&request=GetMap&layers=uv&SRS=EPSG:4326&BBOX=-180,-90,179,91&WIDTH=1000&HEIGHT=800&format=image/png&STYLES=

Expected

Expected behaviour would be, that all requests show (almost) the same image.

MapServer version and installation method

MapServer 8.0.0 and MapServer 8.0.1 on Debian in singularity-container

Mapfile

MAP
PROJECTION
"init=epsg:4326"
END
SYMBOL
NAME "horizline"
TYPE VECTOR
POINTS
0 0
1 0
END # points
END # symbol
SYMBOL
NAME "arrowhead"
TYPE vector
FILLED true
#ANCHORPOINT 0 0.5
POINTS
0 2
4 1
0 0
END # points
END # symbol
SYMBOL
NAME "arrowtail"
TYPE vector
FILLED true
ANCHORPOINT 1 0.5 # to shift the arrowtail
POINTS
0 2
4 1
0 0
-99 -99
0 1
4 1
END # points
END # symbol
LAYER
NAME "uv"
TYPE POINT
STATUS DEFAULT
CONNECTIONTYPE uvraster
DATA /config/entwurf/data/uv_wms/uv_field.grib
PROCESSING "BANDS=1,2"
PROCESSING "UV_SPACING=40"
PROCESSING "UV_SIZE_SCALE=0.2"
CLASS
STYLE
SYMBOL "horizline"
ANGLE [uv_angle]
SIZE [uv_length]
WIDTH 3
COLOR 100 255 0
END # style
STYLE
SYMBOL "arrowhead"
ANGLE [uv_angle]
SIZE 10
COLOR 255 0 0
POLAROFFSET [uv_length_2] [uv_angle]
END # style
STYLE
SYMBOL "arrowtail"
ANGLE [uv_angle]
SIZE 10
COLOR 255 0 0
POLAROFFSET [uv_length_2] [uv_minus_angle]
END # style
END # class
PROJECTION
AUTO
END
METADATA
"ows_enable_request" "*"
"wms_title" "Test"
"wms_srs" "EPSG:4326 EPSG:3857"
"wms_description" "Test Layer"
END

END # layer
END

Attachments

Image 1

Image 2

Image 3

[geographika]

Is there any difference if you set an EXTENT property on the MAP and LAYER (covering the world)?

[kaiwirt]

No, the problem also occurs with EXTENT set on map and layer.
I have the impression that the problem happens, when the region that should be displayed is smaller, than what the data covers.

I attached another example where the data ranges from (0,0) to (30,90) and the problem happens if i want to draw from (0,0) to (29,89)

OK

Not ok

[geographika]

@kaiwirt is the dataset you're using available publicly for download?

[kaiwirt]

@geographika I've uploaded the data and the map file to https://github.com/kaiwirt/uvraster

[geographika]

@kaiwirt - I've recreated that Mapfile at https://app.mapserverstudio.net/#E8RzxwLm, however the BBOX requests seem to return very similar images for me. I have seen vector data go missing from a WMS request before so I think there is an issue somewhere, but it is hard to recreate.

BBOX=-180,-90,179,90

https://api.mapserverstudio.net/mapserver/?map=/etc/mapserver/mapfiles/output/1122c0f4-9929-42ca-b090-97e4c2b22bd0.map&service=WMS&version=1.1.1&request=GetMap&layers=countries,uv&SRS=EPSG:4326&BBOX=-180,-90,179,90&WIDTH=1000&HEIGHT=800&format=image/png&STYLES=

BBOX=-180,-90,179,91

https://api.mapserverstudio.net/mapserver/?map=/etc/mapserver/mapfiles/output/1122c0f4-9929-42ca-b090-97e4c2b22bd0.map&service=WMS&version=1.1.1&request=GetMap&layers=countries,uv&SRS=EPSG:4326&BBOX=-180,-90,179,91&WIDTH=1000&HEIGHT=800&format=image/png&STYLES=

[kaiwirt]

@geographika: I just figured out, that this happens on my system if i set PROJECTION = AUTO on the layer. If i use PROJECTION init=epsg:4326 on the layer everything seems to work.

I find this in my error log
msResampleGDALToMap(): Either map or layer projection is NULL, assuming compatible.
PROJ: Error: proj_as_wkt: missing required input

My proj is Rel. 9.1.1, December 1st, 2022

Maybe an issue in the proj library?

[sdlime]

Might be good to get a quick comment from @rouault.

[rouault]

as your source file is a GRIB dataset and GRIB almost never use EPSG:4326 but other geographic CRS with different datum or ellipsoid shape, if you specify PROJECTION AUTO and request GetMap on EPSG:4326, then a reprojection will occur between the GRIB CRS and EPSG:4326. I would have said that it was then expected that latitude > 90 are going to cause errors, but it seems the other way round.
Actually the issue might be more with the extent of the grid dataset that goes outside [-180,180]x[-90,90]:

Origin = (-180.125000000000000,90.125000000000000)
Pixel Size = (0.250000000000000,-0.250000000000000)
Corner Coordinates:
Upper Left  (-180.1250000,  90.1250000) (180d 7'30.00"W, 90d 7'30.00"N)
Lower Left  (-180.1250000, -90.1250000) (180d 7'30.00"W, 90d 7'30.00"S)
Upper Right ( 179.8750000,  90.1250000) (179d52'30.00"E, 90d 7'30.00"N)
Lower Right ( 179.8750000, -90.1250000) (179d52'30.00"E, 90d 7'30.00"S)
Center      (  -0.1250000,   0.0000000) (  0d 7'30.00"W,  0d 0' 0.01"N)

Perhaps one of the heuristics in mapuvraster.c doesn't work, or one is lacking. Such global datasets touching/crossing the poles/the antimeridian are a source of huge headaches from implementation point of view.