[MapServer-users] WCS no data issuse

[Aleš Grlj]

Hi,

1. For me, specifying

wcs_nilvalues" "-9999"


in the mapfile layer metadata worked and WCS returns non-zero and
transparent no data. -9999 is no data value of my rasters read from the
database but it should work on other storages too.

2. MapServer will not aggregate mosaics for you as far as I know. It will
respect the order in which rasters are called and present no data pixels
even if they overlay valid data pixels from previous raster. And the same
goes for vrts.

If your rasters are stored in the database you could probably specify a
simple query to do a maximum value aggregation on rasters before MapServer
renders them as mosaic. That is if your no data value is lower than valid
values and if this is applicable for your datasets of course. To my
knowledge connection to raster database table is treated as regular
path/url so you have to mind the length of the query. At least I had huge
problems with this.

Cheers

Aleš


V čet., 17. avg. 2023, 21:01 je oseba <
mapserver-users-request at lists.osgeo.org> napisala:

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> Today's Topics:
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>    1. How to handle NoData in WCS Request? Continuation of [Speed
>       of WMS vs Speed of WCS; How to speed up WCS service?]
>       (Marcin Niemyjski)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 17 Aug 2023 08:41:09 +0000
> From: Marcin Niemyjski <mniemyjski at cloudferro.com>
> To: Marcin Niemyjski via MapServer-users
>         <mapserver-users at lists.osgeo.org>
> Subject: [MapServer-users] How to handle NoData in WCS Request?
>         Continuation of [Speed of WMS vs Speed of WCS; How to speed up WCS
>         service?]
> Message-ID:
>         <
> AS1PR03MB8149999665D8BB6C998C3032A81AA at AS1PR03MB8149.eurprd03.prod.outlook.com
> >
>
> Content-Type: text/plain; charset="utf-8"
>
> Hello,
>
>
> Regarding the topic discussed in
> https://marc.info/?l=mapserver-users&m=169049275409489&w=2, I have
> implemented Jukka's suggestions. I created two new attributes, "start" and
> "stop." Here's the improved mapfile:
>
> https://pastecode.io/s/myjemd1r
> As you can see, there are 4 layers served from two tile indexes. The first
> layer consists of preprocessed OCGs with burned NoData, while the remaining
> three are served through VRT targeting different spatial resolutions
> depending on the requested zoom level, with the alpha channel set as a
> cloud mask. Here's an example of such a VRT (the others are similar):
> https://pastecode.io/s/af2tiwsj
>
>
> What is the problem?
>
>   1.  When I try to create a cloudless mosaic using this request for data
> stored in COGs for a single day and there is data available for the
> requested area, the raster is returned. However, instead of transparent
> NoData, a value of 0 is burned in the place of transparent NoData, and I
> need NoData transparency (it's a must-have).
>
>
> http://localhost/cgi-bin/mapserv?map=/var/www/mapbender/piramida_cloudless2.map&service=WCS&version=1.0.0&request=GetCoverage&coverage=test3&BBOX=3180020.455126192886,5542878.218003957532,3184499.682433307637,5548362.511879335158&CRS=EPSG:3857&WIDTH=771&HEIGHT=944&FORMAT=GTiff&start=2023-07-01&stop=2023-07-01
>
>   2.  When I try to create a cloudless mosaic using this request for data
> stored in COGs for multiple days(!), a black tile filled with values of 0
> is returned. This happens because there were no S2 revisions over that area
> for those days, except for 2023-07-01, but data from that day were covered
> with NoData from other days - this is an undesired effect :(
>
>
> http://localhost/cgi-bin/mapserv?map=/var/www/mapbender/piramida_cloudless2.map&service=WCS&version=1.0.0&request=GetCoverage&coverage=test3&BBOX=3180020.455126192886,5542878.218003957532,3184499.682433307637,5548362.511879335158&CRS=EPSG:3857&WIDTH=771&HEIGHT=944&FORMAT=GTiff&start=2023-07-01&stop=2023-07-0
> <
> http://localhost/cgi-bin/mapserv?map=/var/www/mapbender/piramida_cloudless2.map&service=WCS&version=1.0.0&request=GetCoverage&coverage=test3&BBOX=3180020.455126192886,5542878.218003957532,3184499.682433307637,5548362.511879335158&CRS=EPSG:3857&WIDTH=771&HEIGHT=944&FORMAT=GTiff&start=2023-07-01&stop=2023-07-01
> >5
>
>   3.  When I try to request data stored in VRT for a single day using this
> request, data is returned, but the alpha channel is not taken into account,
> so once again, transparency information is omitted.
>
>
> http://localhost/cgi-bin/mapserv?map=/var/www/mapbender/piramida_cloudless2.map&service=WCS&version=1.0.0&request=GetCoverage&coverage=test&BBOX=3180020.455126192886,5542878.218003957532,3184499.682433307637,5548362.511879335158&CRS=EPSG:3857&WIDTH=771&HEIGHT=944&FORMAT=GTiff&start=2023-07-01&stop=2023-07-01
>
> also, WCS seems to ignore MAXSCALEDENOM and MINSCALEDENOM ?
>
>
> Last time, I received a lot of good advice that greatly pushed and
> improved my service. This time, I hope my message will initiate an
> interesting discussion.
>
>
> Best,
>
> Marcin
>
>
>
>
>
>
>
>
>
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