[mapserver-users] WCS Tile index question

[Rahkonen Jukka (MML)]

Hi,

I was just about to suggest to use DEBUG. GDAL does not use “wcs_native_format”, it is used for setting what will be written into DescribeCoverage.

-Jukka Rahkonen-

Lähettäjä: Carl Godkin <cgodkin at gmail.com>
Lähetetty: torstai 21. lokakuuta 2021 1.50
Vastaanottaja: Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi>
Aihe: Re: [mapserver-users] WCS Tile index question

Sorry, right after I sent that last reply to the list, I thought of turning up the DEBUG value in the mapfile to 5 and now I see it's not finding my .hgt files for some reason.

I will dig into this; maybe mapserver + GDAL don't actually needs wcs_native_format.

More later to the list if I sort this out.  I really appreciate the help you and Jeff and others on the list have given me!

carl

On Tue, Oct 19, 2021 at 5:37 PM Rahkonen Jukka (MML) <jukka.rahkonen at maanmittauslaitos.fi<mailto:jukka.rahkonen at maanmittauslaitos.fi>> wrote:
Hi,

Here is more accurate documentation but only in the text https://www.mapserver.org/ogc/wcs_server.html

“The convention is that once (wcs|ows)_extent and one of (wcs|ows)_size and (wcs|ows)_resolution is set in the layer metadata, all the coverage specific metadata will be retrieved from there. Otherwise the source image is queried via GDAL, if possible.”

It seems that only wcs_extent is documented in the list of metadata elements but this is what they do:

  *   wcs_extent defines the bounding box or your coverage -> that will go into DescribeCoverage
  *   wcs_size is the size of the coverage as pixels -> pixel size can be computed by extent and size
  *   wcs_resolution tells the pixel size explicitly -> size of the coverage in pixels can be computed

We have in the LAYER-METADATA:
"wcs_resolution" "0.5 0.5"
"wcs_extent"          "19970 6597278 749676 7785300"

That should be enough and Describe Coverage will have correct limits, origin, and offset vectors in RectifiedGrid.

-Jukka Rahkonen-


Lähettäjä: MapServer-users <mapserver-users-bounces at lists.osgeo.org<mailto:mapserver-users-bounces at lists.osgeo.org>> Puolesta Carl Godkin
Lähetetty: keskiviikko 20. lokakuuta 2021 1.17
Vastaanottaja: mapserver-users at lists.osgeo.org<mailto:mapserver-users at lists.osgeo.org>
Aihe: [mapserver-users] WCS Tile index question

Hi again,

I am working with Mapserver trying to set up a WCS layer based on a large collection of SRTM .hgt files.

Since I have many input files instead of a single file, I want to use a tile index.  I know how to make and use a tile index for WMS, but there's a twist for WCS that I don't understand.

According to this section of the docs:
 https://mapserver.org/optimization/tileindex.html?highlight=wcs_resolution#note-for-wcs-layers
<https://mapserver.org/optimization/tileindex.html?highlight=wcs_resolution#note-for-wcs-layers>

I need to set “wcs_extent”, “wcs_size”, and “wcs_resolution” but I don't see where they are defined or documented.

Can you point me to documentation?  The WCS Use Cases page gives some hints so I think I understand wcs_extent (though it's "ows_extent" in some examples there so I guess these are interchangeable?)

How are the others defined?

Thank you for your help,
carl


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