<div dir="auto">Hi Patrick,<div dir="auto"><br></div><div dir="auto">Sorry for asking, did you create pyramids (overlays) for your raster "tiles"?</div><div dir="auto"><br></div><div dir="auto">See more information about pyramids on QGIS official documentation:</div><div dir="auto"><br></div><div dir="auto"><a href="https://docs.qgis.org/3.4/en/docs/user_manual/working_with_raster/raster_properties.html#pyramids-properties">https://docs.qgis.org/3.4/en/docs/user_manual/working_with_raster/raster_properties.html#pyramids-properties</a><br></div><div dir="auto"><br></div><div dir="auto">To create pyramids on many files, it's probably better to use GDAL directly to process all files in a folder:</div><div dir="auto"><br></div><div dir="auto"><a href="https://gdal.org/programs/gdaladdo.html">https://gdal.org/programs/gdaladdo.html</a><br></div><div dir="auto"><br></div><div dir="auto">My feeling is that the WMS service is doing that for you, and that's the reason why it works well with a service.</div><div dir="auto"><br></div><div dir="auto">Alexandre Neto</div><div dir="auto">QGIS Support</div><div dir="auto"><a href="http://www.qcooperative.net">www.qcooperative.net</a></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">A segunda, 18/11/2019, 09:11, Patrick Dunford <<a href="mailto:enzedrailmaps@gmail.com">enzedrailmaps@gmail.com</a>> escreveu:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<p>Good day to all</p>
<p>One of the user experiences I have had from using the Qgis
software has been with projects using large numbers of raster tile
layers. These layers are generally tiles that have a size of
4800x7200 pixels in GeoJPEG format and have either been downloaded
directly from tile servers to these locally stored files, or
created from downloaded tiles with other layers overlaid in Gimp
projects.</p>
<p>There appears to be some architectural limit in Qgis desktop
software relating to either the total number of raster layer
[files] in a project or to the total number of pixels in raster
layer [files] in a project. This is unrelated to the number of
layers or pixels currently enabled for display in the map canvas.
In practice, the appearance of this limit is that it is kicking in
long before the host computer's own physical resources are
anywhere near fully engaged. Map digitising and editing is done on
systems with 32 GB of physical memory (RAM) and 200 GB of
SSD-based virtual memory (swap) and these systems are able to edit
very large Gimp projects for user tile creation that often engage
all of the system's physical memory and around 100 GB of the
virtual memory without problems. But these types of numbers are in
practice never seen with Qgis projects when the raster layer limit
is being seen.</p>
<p>The appearance of a raster layer limit is generally experienced
in older versions of the software by layers being displayed on the
canvas as garbage, and in newer versions by the software crashing.
It will only start working again if raster layers are removed from
the project. However, when layers are loaded from WMTS servers, no
appearance of limitation is seen.</p>
<p>The question to be answered, then, is which of any possible range
of resolutions would be appropriate or useful to this predicament.
With only limited understanding of the architectural design of the
software, it would seem the following options exist:</p>
<ol>
<li>File a bug report for the software concerning a possible issue
with the design of the product</li>
<li>Amalgamate smaller tiles into larger ones (e.g. 48 tiles at
4800x7200 can be put into one tile at 57600x28800). This only
works if the software issue is related to the number of file
based tile layers and not to the total number of pixels in those
layers.</li>
<li>Post a feature request for sub-project capabilities. This
would allow a project that combines vector and raster layers, to
be split into one project containing the vector layers and a
number of projects each of which contains the vector project as
a subproject and a certain subset of all the raster layers that
is smaller than the observable limit.</li>
<li>Set up my own local WMTS server to serve all the raster layers
to my map editing projects.</li>
<li>Explore the possibilities of preconfigured limits in the
operating system that may need to be increased to overcome file
based layer limits in projects (such as the NOFILES limit in
Linux, currently set at 10,000 hard and soft on map editing
computers)</li>
</ol>
<p>Is anyone who is knowledgeable about the architecture of the Qgis
desktop software able to comment with some detail about possible
resolutions.</p>
<p><br>
</p>
</div>
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