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I'm trying to generate some tiles from a very large dataset (5.8 million points). Each point represents a 20 x 20 grid square in the OSGB 1936 / National Grid CRS.

What I'd like is for each square to be coloured according to some property of the point. I've made very good progress by making my marker a square of size 20 map units, with a graduated colouring.

The issue I'm having (besides the time it takes to generate the tiles) is that the output tiles have very noticeable artefacts, that look like the kind of patterns you get when sampling an image at the wrong rate.

Example Tile

I think this is because the markers don't align to a perfect grid. Even in the QGIS viewer, I can see tiny light-coloured lines in between each marker.

There are two options I can think of:

  1. Improve the sampling rate of QTiles
  2. Fix the underlying issue of the markers not exactly lining up with the grid

Are there any ideas on how I can do either of these, or any other ways to improve the look of the tiles?

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