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Hi,</div>
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Off the top of my head...</div>
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Postgis can easily cope with millions of records. Given the points are there, use that to create the hexagons as required - this can be done using
<a href="https://postgis.net/docs/ST_HexagonGrid.html" id="LPlnk">https://postgis.net/docs/ST_HexagonGrid.html</a></div>
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<div class="elementToProof">If you set up your QGIS project with preset zoom levels, and create a set of appropriately sized hexagons for each zoom level, then populate a column with the number of points it contains.</div>
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There will be some devilish details - as you zoom in, the polygon's real area will get smaller, so will contain less points. A fixed symbology will therefore change the colour range with the scale.</div>
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Calculating a normalised value, perhaps something like instead of the no of points, you calculate a normalised value - the hex at each scale with the most points gets 100, the rest get a value based on the no of points/the max for that scale, so all polygon
datasets will have colours set to values between 0 and 100. All doable with SQL.</div>
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Do all the data stuff in Postgis, then just plot in QGIS.</div>
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There are various ways to set QGIS up for this, but one reasonably straightforward way that should work is having a separate hexagon layer for each scale, with a scale limit on displaying it so that all map scales are represented by one of the hexagon layers,
with the fixed zoom levels/scales, set the same symbology for each layer, then group them into a single group.</div>
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Something to consider anyway...</div>
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Cheers</div>
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Brent Wood<br>
<br>
Principal Technician, Fisheries<br>
NIWA<br>
DDI: +64 (4) 3860529</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> QGIS-User <qgis-user-bounces@lists.osgeo.org> on behalf of Sylvain Ard via QGIS-User <qgis-user@lists.osgeo.org><br>
<b>Sent:</b> Friday, March 14, 2025 23:35<br>
<b>To:</b> qgis-user@lists.osgeo.org <qgis-user@lists.osgeo.org><br>
<b>Subject:</b> [Qgis-user] question</font>
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<div>Hello,<br>
I'd like a map with hexagons that are darker the more points there are underneath. My points are in a PostgreSQL table. If there are no points, there should be no hexagon. The hexagons have a constant size on the screen, so they have to be recalculated each
time the map is zoomed in. I want a truly optimized solution because I have millions of points. So, perhaps I could use QGIS-server.<br>
Please suggest a solution for both the server and client side.<br>
Best regards</div>
<div>PS : my map must be like GBIF maps</div>
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<div>Sylvain Ard<br>
0549507724<br>
0778380991</div>
<div><a href="mailto:sylvain.ard@gmail.com" target="_blank">sylvain.ard@gmail.com</a></div>
<div><a href="http://sylvain-ard.fr/" originalsrc="http://sylvain-ard.fr/" target="_blank">https://www.sylvain-ard.fr</a><br>
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Entreprise individuelle SIRET : 80079243400022<br>
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<span>Brent Wood <br>
<font color="#1793d2">Principal Technician - GIS and Spatial Data Management</font><br>
<font color="#1793d2">Programme Leader - Environmental Information Delivery</font><br>
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