[mapserver-users] Reprojection error for CONNECTIONTYPE WMS

[Simon.Schneegans at dlr.de]

Hi there!

I tested some more and it seems that this is not only a problem for WMS layers, but for Raster layers as well. Here is an example GeoTiff:
https://github.com/mapserver/mapserver/files/1047153/test.zip

I can warp this to HEALPix using GDAL on the command line:
gdalwarp -t_srs '+proj=healpix +a=1 +b=1 +wktext' -te -0.5 0.6 0.5 1  test.tiff healpix.tiff

The result looks as supposed (see example in the original issue: https://github.com/mapserver/mapserver/issues/5437).
However, if I let mapserver do the reprojection, the result is distorted (e.g. Libya is missing on the map). This is my layer (except for some metadata):

LAYER
    name "test"
    status ON
    type RASTER
    data "test.tiff"

    PROJECTION
        AUTO
    END
END

This is in my epsg file:

<900916> +proj=healpix +a=1 +b=1 <>

This is the relevant part of the WMS request:

...&LAYERS=test&WIDTH=600&HEIGHT=300&SRS=EPSG:900916&BBOX=-0.5,0.6,0.5,1

The example test.tiff I linked above covers exactly the area I am requesting to be reprojected to HEALPix. As soon as this input tiff is larger, the reprojection works as supposed. I guess that this is the reason why I observed the issue with CONNECTIONTYPE WMS first: Here the input data is usually exactly as large as required by the reprojection!

Where do I have to go bug hunting? Is it a configuration issue? Is it a reprojection issue specific to HEALPix?

Thank you for your support!
Simon



Von: mapserver-users [mailto:mapserver-users-bounces at lists.osgeo.org] Im Auftrag von Simon.Schneegans at dlr.de
Gesendet: Dienstag, 30. Mai 2017 13:17
An: mapserver-users at lists.osgeo.org
Betreff: [mapserver-users] Reprojection error for CONNECTIONTYPE WMS

Hi there!

I am happily using mapserver to reproject raster data  to the HEALPix projection from proj.4<http://proj4.org/projections/healpix.html>. This works pretty well for local raster sources, however I get severe reprojection problems when using an external WMS as source for my layer.

I reported this issue on Github (https://github.com/mapserver/mapserver/issues/5437) but was told to ask here for assistance. Instead of copy-pasting the text from the Github issue to this mail, I kindly ask you to refer to this Github issue for further information; there I also included several images illustrating the problem.

I am looking forward to get any feedback or input that helps me solving this issue!

Thank you very much!
Simon

--------------------------
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
German Aerospace Center
Simulation and Software Technology | Software for Space Systems and Interactive Visualization | Lilienthalplatz 7 | 38108 Braunschweig | Germany

Simon Schneegans, M. Sc.
Telephone +49 531 295-2333 | Telefax +49 531 295-12100  | simon.schneegans at dlr.de<mailto:simon.schneegans at dlr.de>
DLR.de<http://www.dlr.de/>

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