WmsRasterSource chooses wrong axis order

Clemens_Ladisch · October 20, 2021, 8:37am

Since version 12.3.13, WmsRasterSource chooses YX order for coordinate systems that actually use XY.

My code is the equivalent of the following; it fails because Open() changes the AxisOrder property from the default:

        var wms = new WmsRasterSource(new Uri("https://inspire.informatievlaanderen.be/raadpleegdiensten/oi/wms"));
        wms.ActiveLayerNames.Add("OI.OrthoimageCoverage.OMW");
        wms.Crs = "EPSG:31370";
        wms.Open();
        // ...
        if (wms.GetServiceVersion().StartsWith("1.3.") &&
            wms.AxisOrder == WmsAxisOrder.Default)
        {
            wms.AxisOrder = LookupAxisOrder(wms.Crs);
        }
        // ...
        Debug.Assert(wms.AxisOrder == WmsAxisOrder.XY); // FAILS

How does WmsRasterSource determine the axis order? The only reliable way I’ve found is to look it up in the EPSG database. Should I give you the list?

Ben · October 22, 2021, 6:34pm

Hi Clemens,

We recently made some changes in WMS RasterSource to smartly set WMS’s AxisOrder based on the CRS for WMS 1.3, apparently we introduced some issues. What is the list you mean exactly, is that the epsg list in which Y is ahead of X? If you have the list, can you let us know where it can be downloaded?

Sorry about the issue. please work it around by manually setting AxisOrder to XY or YX for now.

And by the way, I really don’t like this dynamic axis order stuff in WMS 1.3, make everything complicated.

Thanks,
Ben

Clemens_Ladisch · October 23, 2021, 7:56pm

The EPSG dataset can be downloaded from epsg.org/download-dataset.html.

To get a list of CRS IDs with YX order (which is much shorter than the XY list), import the dump into Postgres and run the following query:

SELECT coord_ref_sys_code
FROM epsg.epsg_coordinatereferencesystem crs
JOIN epsg.epsg_coordinateaxis ax USING (coord_sys_code)
WHERE crs.coord_ref_sys_kind IN ('projected', 'geographic 2D')
  AND crs.show_crs = 1
  AND ax.coord_axis_order = 1
  AND coord_axis_orientation NOT IN ('east', 'west')
ORDER BY 1

result:

Ben · October 25, 2021, 4:22pm

Thanks! we will integrate it in.

Leo_Liu · October 27, 2021, 3:44pm

hi Clemens,

We’ve integrated it in our code. You could upgrade your ThinkGeo.Core to 13.0.0-beta305 or above and give it a try. The new build will be available in several hours.

Thanks,
Leo