[MapServer-users] WMS requests over the antimeridian : inconsistent responses, depending on east or west side

[Philippe Ghesquiere]

Dear all,

I noticed a weird behaviour with a WMS request based on EPSG:4326, when the
BBOX exeeds the [-180 ; +180] longitude intervalle.
We bump into this problem when we try to display images over the
antimeridian line.

I could observe this problem with the "MapServer Demonstration Server".


*Observed*Mapserver response is not consistent whether the BBOX overlaps
eastward or westward :
1) Westward
BBOX=-90,-200,90,100
The image is clipped on both east and west sides, that is in the [-180° ;
+100°] longitude intervalle.
On the west side, pixels in the [-200° ; -180°] longitude intervalle are
transparent.

The complete request URL is :
https://demo.mapserver.org/cgi-bin/wms?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=-90,-200,90,100&CRS=EPSG:4326&WIDTH=953&HEIGHT=480&LAYERS=bluemarble&STYLES=&FORMAT=image/png&TRANSPARENT=true&STYLES=

2) Eastward
BBOX=-90,-100,90,200
The image is clipped on the west side, which is OK.
On the east side, pixels in the [+180°; +200°] longitude intervalle are not
correct.

The complete request URL is :
https://demo.mapserver.org/cgi-bin/wms?SERVICE=WMS&VERSION=1.3.0&REQUEST=GetMap&BBOX=-90,-100,90,200&CRS=EPSG:4326&WIDTH=953&HEIGHT=480&LAYERS=bluemarble&STYLES=&FORMAT=image/png&TRANSPARENT=true&STYLES=



*Expected*At least, I would expect to have the same behaviour on both sides
of the antimeridian.

Furthermore, couldn't we get the "repeated world" on the [-200° ; -180°]
(respectively [+180° ; +200°]) longitude intervalle ?

Thanks for your help
Philippe
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