[gdal-dev] GDAL WMTS get tiles no documentation

[Michał Kowalczuk]

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.

Regards
Michal

W dniu śr., 29.05.2024 o 10:04 Rahkonen Jukka <
jukka.rahkonen at maanmittauslaitos.fi> napisał(a):

> Hi,
>
>
>
> No, I am not sure because I do not program myself. Reading this document
> https://gdal.org/user/multithreading.html makes me feel that it is
> possible to do some things in parallel, but the programmer must know how to
> do it right.
>
>
>
> -Jukka Rahkonen-
>
>
>
> *Lähettäjä:* Javier Jimenez Shaw <j1 at jimenezshaw.com>
> *Lähetetty:* keskiviikko 29. toukokuuta 2024 10.41
> *Vastaanottaja:* Rahkonen Jukka <jukka.rahkonen at maanmittauslaitos.fi>
> *Kopio:* Michał Kowalczuk <michkowalczuk at gmail.com>;
> gdal-dev at lists.osgeo.org
> *Aihe:* Re: [gdal-dev] GDAL WMTS get tiles no documentation
>
>
>
>
>
>
>
> On Wed, 29 May 2024 at 08:59, Rahkonen Jukka via gdal-dev <
> gdal-dev at lists.osgeo.org> wrote:
>
> Hi,
>
>
>
> 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
> https://gdal.org/tutorials/raster_api_tut.html#reading-raster-data “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.
>
>
>
> 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
> https://rasterio.readthedocs.io/en/latest/topics/concurrency.html.
>
>
>
> 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.
>
>
>
>
>
> -Jukka Rahkonen-
>
>
>
> *Lähettäjä:* gdal-dev <gdal-dev-bounces at lists.osgeo.org> *Puolesta *Michal
> Kowalczuk via gdal-dev
> *Lähetetty:* keskiviikko 29. toukokuuta 2024 9.08
> *Vastaanottaja:* gdal-dev at lists.osgeo.org
> *Aihe:* [gdal-dev] GDAL WMTS get tiles no documentation
>
>
>
> Hi GDAL fellows
>
> This is my first post on this mailing list, so I'm asking for
> understanding.
>
>
>
> As all we know the purpose of using WMTS over WMS, I'd like to implement
> parallel downloading tiles from service using C API.
>
> In my opinion GDAL documentation (
> https://gdal.org/drivers/raster/wmts.html) says nothing on this topic.
>
> 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.
>
>
>
> 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.
>
>
>
> Thank you!
>
> Michal
>
> _______________________________________________
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> gdal-dev at lists.osgeo.org
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>
>
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