[mapserver-users] Nodata in raster queries

[Frank Warmerdam]

On 11-03-14 03:23 PM, Boss, Ken (DNR) wrote:
> I have a DEM that I am using with mapserver 5.6 to service queries for an elevation value at a given point.  The DEM contains significant offsite/nodata areas.  From gdalinfo:
>
> Band 1 Block=19063x1 Type=Int16, ColorInterp=Gray
>     NoData Value=-32768
>
> If I open the image in QGIS and use the identify tool over a nodata area, it says:
>
>    Band 1  null (no data)
>
> But when I run a mapserver point query at the same point, the value returned is -32768.  Is there a way to configure mapserver to return something more like null for raster nodata areas?

Ken,

Mapserver has a few mechanisms for specifying nodata.  I skimmed the
raster query code and it does not seem to honour these.  If you file
a ticket on this issue, I can try and implement nodata support in the
raster query code this week at the code sprint.

In MapServer 6.0 (trunk) there are some improvements to detecting nodata
values, even for non-8bit data, in the raster drawing case.  This just
hasn't all made it into the raster query logic.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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