serving sparse DTED with WCS

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serving sparse DTED with WCS

gbburkhardt
DTED data is notoriously sparse.  If one combines all the files in a DTED dataset into a single Geotiff file using something like " gdalwarp -co TILED=YES */*.dt2 dted2.tif"

But GDAL will build a bounding box that's square with the world, and there might not be data for every 1x1 deg section of the bounding box.

When this happens, Mapserver fills in the missing data with zeros.  Additionally, there might be data missing from within a 1x1 deg DTED file, and it is marked with a  NODATA flag of -32767.  

Is there some way for Mapserver to communicate to a client where data is missing?  I can't find anything in the coverage information provided to a WCS 1.0.0 client.

Thanks.
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Re: serving sparse DTED with WCS

Even Rouault-2
On mercredi 4 avril 2018 19:51:56 CEST Burkhardt, Glenn B        UTAS wrote:

> DTED data is notoriously sparse.  If one combines all the files in a DTED
> dataset into a single Geotiff file using something like " gdalwarp -co
> TILED=YES */*.dt2 dted2.tif"
>
> But GDAL will build a bounding box that's square with the world, and there
> might not be data for every 1x1 deg section of the bounding box.
>
> When this happens, Mapserver fills in the missing data with zeros.
> Additionally, there might be data missing from within a 1x1 deg DTED file,
> and it is marked with a  NODATA flag of -32767.
>
> Is there some way for Mapserver to communicate to a client where data is
> missing?  I can't find anything in the coverage information provided to a
> WCS 1.0.0 client.

Glenn,

You can define in the LAYER.METADATA section things like for WCS 1.0 and WCS
1.1

"wcs_rangeset_nullvalue" "-32767"

Actually I see this wasn't documented. I've just added it in
http://mapserver.org/ogc/wcs_server.html

For WCS 2, use "wcs_nilvalues"

Even

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Re: [External] Re: serving sparse DTED with WCS

gbburkhardt
This works perfectly for me.  Missing 1x1 deg tiles from a bounding box are correctly reported as missing, and if there is missing data within a tile, it also is reported as missing.  Thanks!

Suggestion for improvement:  when the data file supplied to Mapserver is Geotiff, and a " NoData Value" is supplied, automatically use it as a null value for the layer.

-----Original Message-----
From: Even Rouault [mailto:[hidden email]]
Sent: Thursday, April 5, 2018 10:02
To: [hidden email]
Cc: Burkhardt, Glenn B UTAS <[hidden email]>
Subject: [External] Re: [mapserver-users] serving sparse DTED with WCS

On mercredi 4 avril 2018 19:51:56 CEST Burkhardt, Glenn B        UTAS wrote:

> DTED data is notoriously sparse.  If one combines all the files in a
> DTED dataset into a single Geotiff file using something like "
> gdalwarp -co TILED=YES */*.dt2 dted2.tif"
>
> But GDAL will build a bounding box that's square with the world, and
> there might not be data for every 1x1 deg section of the bounding box.
>
> When this happens, Mapserver fills in the missing data with zeros.
> Additionally, there might be data missing from within a 1x1 deg DTED
> file, and it is marked with a  NODATA flag of -32767.
>
> Is there some way for Mapserver to communicate to a client where data
> is missing?  I can't find anything in the coverage information
> provided to a WCS 1.0.0 client.

Glenn,

You can define in the LAYER.METADATA section things like for WCS 1.0 and WCS
1.1

"wcs_rangeset_nullvalue" "-32767"

Actually I see this wasn't documented. I've just added it in http://mapserver.org/ogc/wcs_server.html

For WCS 2, use "wcs_nilvalues"

Even

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