[MapServer-users] uvraster using vrt files from tileitem fails: GDALRasterIO() failed

[Trygve Aspenes]

Sorry

Somehow I managed to send the email before I had completed it.

Here is all again

> Hello
> 
> I have a layer using uvraster as connectiontype, with the data comming 
> from a helper layer via tileitem.
> 
> So the helper layer is like this:
> 
> 	LAYER
> 		PROJECTION
> 			"init=epsg:3857"
> 		END
> 		STATUS ON
> 		NAME "time_idx_vrt"
> 		TYPE POLYGON
> 		PROCESSING "CLOSE_CONNECTION=DEFER"
> 		DATA "geom from (select * from <table>) as foo using unique id using 
> srid=3857"
> 		METADATA
> 			"wms_title" "x_timeindex"
> 			"wms_timeextent" "<time extent>"
> 			"wms_timeitem" "time"
> 			"wms_timedefault" "<default_time>"
> 			"wms_enable_request" "!*"
> 			"wms_srs"  "EPSG:3857"
> 		END
> 		CONNECTIONTYPE postgis
> 		CONNECTION "<connection parametes"
> 	END
> 
> 
> And the layer:
>     LAYER
>         DEBUG 5
>         NAME "TestLayer"
>         METADATA
>             "wms_title" "Test Layer"
>             "wms_srs" "EPSG:3857"
>             "wms_timeextent" "<extent>"
>             "wms_enable_request" "*"
>             "wms_include_items" "all"
>         END
>         VALIDATION
>             "TIME" "^[-0-9TZ:]{20}$"
>             "DEFAULT_TIME" "<default time>"
>         END
> 		TILEITEM "filename"
> 		TILEINDEX "time_idx_vrt"
> 
>         PROCESSING "BANDS=1,2"
>         TYPE POINT
>         STATUS ON
>         CONNECTIONTYPE uvraster
>         PROJECTION
>             "init=EPSG:3857"
>         END
> 
>         <all the class definition>
> END

Here is what I get for that Layer in GetCapabilities:
     <Layer queryable="0" opaque="0" cascaded="0">
         <Name>TestLayer</Name>
         <Title>Test Layer</Title>
         <CRS>EPSG:3857</CRS>
         <EX_GeographicBoundingBox>
             <westBoundLongitude>-0.628279</westBoundLongitude>
             <eastBoundLongitude>7.561219</eastBoundLongitude>
             <southBoundLatitude>69.874435</southBoundLatitude>
             <northBoundLatitude>71.893538</northBoundLatitude>
         </EX_GeographicBoundingBox>
         <BoundingBox CRS="EPSG:3857"
                     minx="-69939.7" miny="1.1028e+07" maxx="841711" 
maxy="1.17149e+07" />
         <Dimension name="time" units="ISO8601" 
nearestValue="0">2025-10-28T17:04:48Z</Dimension>
         <MetadataURL type="TC211">
           <Format>text/xml</Format>
           <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
xlink:type="simple" xlink:href="https://<path to 
server>/wms?request=GetMetadata&layer=TestLayer"/>
         </MetadataURL>
         <Style>
           <Name>default</Name>
           <Title>default</Title>
           <LegendURL width="127" height="320">
              <Format>image/png</Format>
              <OnlineResource xmlns:xlink="http://www.w3.org/1999/xlink" 
xlink:type="simple" xlink:href="https://<path to 
server>/wms?version=1.3.0&service=WMS&request=GetLegendGraphic&sld_version=1.1.0&layer=TestLayer&format=image/png&STYLE=default"/>
           </LegendURL>
         </Style>
     </Layer>

Looks good to me. It gets the extents, so it clearly reads the vrt file.

So here is what I get when I try a getMap request:

<?xml version='1.0' encoding="UTF-8" standalone="no" ?>
<ServiceExceptionReport version="1.3.0" 
xmlns="http://www.opengis.net/ogc" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
xsi:schemaLocation="http://www.opengis.net/ogc 
http://schemas.opengis.net/wms/1.3.0/exceptions_1_3_0.xsd">
<ServiceException>
msDrawMap(): Image handling error. Failed to draw layer named 
'TestLayer'.
msUVRASTERLayerWhichShapes(): General error message. Unable to draw 
raster data.
msDrawRasterLayerGDAL_RawMode(): Unable to access file. GDALRasterIO() 
failed: NETCDF:<path to netcdf file>:<variable_name>: No such file or 
directory
</ServiceException>
</ServiceExceptionReport>


So it clearly gets the vrt file from the tileitem, open the vrt and find 
the file name of the first band. Then when mapserver tries to read some 
of the data from netcdf file it says no such file or directory.

And here is the problem. The file is cleary there. If I try with 
gdalinfo on both  the vrt file, and the netcdf file I get what I expect.

So what can be different in mapserver compared to what gdalinfo sees?

In the past I have seen problems with shapepath, but I have set 
shapefile "" ( ie empty) in the map file to avoid this. But still the 
problems.

Any idea what I can to fix this?

Trygve Aspenes