<div dir="ltr">Hi, thank you for your replies!<br>As I'm still a newbie especially with WMTS. I need to take a step back to the basics. Let's forget about multithreading for now.<div><ul><li>I'm in the stage that I can open a dataset using WMTS service path from data provider</li><li>I can list subdatasets and open the selected layer as a new dataset using path from <b>SUBDATASET_id_NAME</b>.</li><li>This dataset reports large height and width values, which is obvious.</li><li>The first question is how to read any fragment from this dataset using <b>GDALDatasetRasterIO</b>.<br>Is there a similar way to <b>SpatialFIlter </b>from vector layers?<br>I see in the docs there is a <b><DataWindow></b> tag for a local service descriptions which defines extents of the data. Does it mean that for each map extent change I need to create a new local XML file and open a new dataset to read demanded bbox?<br>Is this the only way for doing it?</li><li>From other site I noticed that QGIS downloads tiles separately? But how it knows which row/col and zoom should be used in GET request? Does it use GDAL for WMTS reading at all?<br><img src="cid:ii_lwuo6shc1" alt="image.png" width="562" height="79"></li></ul>I will be grateful for any tip and trucks for a newbie ;-)</div><div><br></div><div>Regards,</div><div>Michal </div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">śr., 29 maj 2024 o 12:41 Even Rouault <<a href="mailto:even.rouault@spatialys.com">even.rouault@spatialys.com</a>> napisał(a):<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><u></u>
<div>
<p>Hi,</p>
<p>The WMS cache (which is used underneath by the WMTS driver)
writes each tiles in a separate file. So if you use
multi-threaded, as long as you read in parallel different
GDALDataset* object on the WMTS filename, and read disjoint areas,
that should be fine. There might be a slight risk of things going
bad if you happened to read the same tile from different
GDALDataset* object at the same time, as it could potentially read
a partially written cached tile, or concurrently write the tile in
the cache and corrupt it. The logic is in
frmts/wms/gdalwmscache.cpp<br>
</p>
<p>Even<br>
</p>
<div>Le 29/05/2024 à 10:14, Michał Kowalczuk
via gdal-dev a écrit :<br>
</div>
<blockquote type="cite">
<div dir="auto">Because this is not clear in documentation,
especially in WMTS driver docs, my question is strictly about
this issue to programmers who have already explored this topic.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Regards</div>
<div dir="auto">Michal</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">W dniu śr., 29.05.2024 o
10:04 Rahkonen Jukka <<a href="mailto:jukka.rahkonen@maanmittauslaitos.fi" target="_blank">jukka.rahkonen@maanmittauslaitos.fi</a>>
napisał(a):<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div style="overflow-wrap: break-word;" lang="FI">
<div>
<p class="MsoNormal"><span lang="EN-US">Hi,</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">No, I am not
sure because I do not program myself. Reading this
document
<a href="https://gdal.org/user/multithreading.html" target="_blank">https://gdal.org/user/multithreading.html</a>
makes me feel that it is possible to do some things
in parallel, but the programmer must know how to do
it right.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">-Jukka Rahkonen-</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">Lähettäjä:</span></b><span lang="EN-US"> Javier Jimenez Shaw <<a href="mailto:j1@jimenezshaw.com" target="_blank">j1@jimenezshaw.com</a>>
<br>
<b>Lähetetty:</b> keskiviikko 29. toukokuuta 2024
10.41<br>
<b>Vastaanottaja:</b> Rahkonen Jukka <<a href="mailto:jukka.rahkonen@maanmittauslaitos.fi" target="_blank">jukka.rahkonen@maanmittauslaitos.fi</a>><br>
<b>Kopio:</b> Michał Kowalczuk <<a href="mailto:michkowalczuk@gmail.com" target="_blank">michkowalczuk@gmail.com</a>>;
<a href="mailto:gdal-dev@lists.osgeo.org" target="_blank">gdal-dev@lists.osgeo.org</a><br>
<b>Aihe:</b> Re: [gdal-dev] GDAL WMTS get tiles no
documentation</span></p>
</div>
</div>
</div>
<div style="overflow-wrap: break-word;" lang="FI">
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
</div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">On Wed, 29
May 2024 at 08:59, Rahkonen Jukka via gdal-dev
<</span><a href="mailto:gdal-dev@lists.osgeo.org" target="_blank"><span lang="EN-US">gdal-dev@lists.osgeo.org</span></a><span lang="EN-US">> wrote:</span></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin:5pt 0cm 5pt 4.8pt">
<div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US">Hi,</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">When
you have a RasterBand from the WMTS
data source, it is abstracted and you
can read the raster data just like from
any other data source and raster band
</span><a href="https://gdal.org/tutorials/raster_api_tut.html#reading-raster-data" target="_blank"><span lang="EN-US">https://gdal.org/tutorials/raster_api_tut.html#reading-raster-data</span></a><span lang="EN-US"> “There are a few ways to
read raster data, but the most common is
via the GDALRasterBand::RasterIO()
method. This method will automatically
take care of data type conversion,
up/down sampling and windowing.” GDAL
knows which tiles to read.</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">I do
not know if the WMTS driver can do
parallel tile downloads. If not, it is
possible to run many RasterIO() at the
same time, each reading data from a
different window like in this rasterio
document </span><a href="https://rasterio.readthedocs.io/en/latest/topics/concurrency.html" target="_blank"><span lang="EN-US">https://rasterio.readthedocs.io/en/latest/topics/concurrency.html</span></a><span lang="EN-US">.</span></p>
</div>
</div>
</div>
</blockquote>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Jukka, are
you sure you can run several RasterIO in
parallel (on the same dataset)? in GDAL
GeoTIFF you cannot: the cache may be
corrupted. In that case I open several
datasets over the same file. I do not know
about WMTS.</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
</div>
<blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0cm 0cm 0cm 6pt;margin:5pt 0cm 5pt 4.8pt">
<div>
<div>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<p class="MsoNormal"><span lang="EN-US">-Jukka
Rahkonen-</span></p>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<div style="border-right:none currentcolor;border-bottom:none currentcolor;border-left:none currentcolor;border-top:1pt solid currentcolor;padding:3pt 0cm 0cm">
<p class="MsoNormal"><b><span lang="EN-US">Lähettäjä:</span></b><span lang="EN-US"> gdal-dev <</span><a href="mailto:gdal-dev-bounces@lists.osgeo.org" target="_blank"><span lang="EN-US">gdal-dev-bounces@lists.osgeo.org</span></a><span lang="EN-US">>
<b>Puolesta </b>Michal Kowalczuk via
gdal-dev<br>
<b>Lähetetty:</b> keskiviikko 29.
toukokuuta 2024 9.08<br>
<b>Vastaanottaja:</b> </span><a href="mailto:gdal-dev@lists.osgeo.org" target="_blank"><span lang="EN-US">gdal-dev@lists.osgeo.org</span></a><span lang="EN-US"><br>
<b>Aihe:</b> [gdal-dev] GDAL WMTS get
tiles no documentation</span></p>
</div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
<div>
<p class="MsoNormal"><span lang="EN-US">Hi
GDAL fellows</span></p>
<div>
<p class="MsoNormal"><span lang="EN-US">This
is my first post on this mailing
list, so I'm asking for
understanding.</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">As
all we know the purpose of using
WMTS over WMS, I'd like to implement
parallel downloading tiles from
service using C API.</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">In
my opinion GDAL documentation (</span><a href="https://gdal.org/drivers/raster/wmts.html" target="_blank"><span lang="EN-US">https://gdal.org/drivers/raster/wmts.html</span></a><span lang="EN-US">) says nothing on this
topic.</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">I
can get capabilities from WMTS, I
can open the selected subdataset but
how to get tiles for given extent? I
could not find any information how
to do it, even in the GDAL tests on
github.</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">I
am kindly asking for tips. It also
can be in python. How using pure
GDAL API fetch tiles to dynamically
complete the displayed map. This is
my goal.</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US"> </span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Thank
you!</span></p>
</div>
<div>
<p class="MsoNormal"><span lang="EN-US">Michal</span></p>
</div>
</div>
</div>
</div>
<p class="MsoNormal"><span lang="EN-US">_______________________________________________<br>
gdal-dev mailing list<br>
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</div>
</blockquote>
</div>
</div>
</div>
</div>
</blockquote>
</div>
</div>
<br>
<fieldset></fieldset>
<pre>_______________________________________________
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</blockquote>
<pre cols="72">--
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My software is free, but my time generally not.</pre>
</div>
</blockquote></div>