Restrict objects to a defined number in a certain area

[bweinlich]

I want to show OSM trees on my map, so I added something like this in the LUA-Script:

-- Write 'tree'
if natural == "tree" then
	node:Layer("tree", false)
	node:Attribute("natural", "tree")
	node:Attribute("leaf_type", node:Find("leaf_type"))
	return
end

This works very well but I recognized that in some cities there are really lots of trees which is a bit overwhelming in certain areas. So I wonder if it is possible to restrict the density of trees (or any other objects). For example a maximum of 10 trees in a 10x10 metres square.

So I would need something like a spatial query around the current object. Is this possible in the Lua script or is there something like a postprocessing step that I can hook into?

Thanks in advance :)

[systemed]

This sort of heavy geometry processing isn't really something that tilemaker does, I'm afraid - you'd typically use PostGIS for this. Martin would be really well suited for serving vector tiles with queries like this.

If you did want to still use tilemaker, you'd typically load the trees into a Postgres database (using osm2pgsql and some custom Lua); cluster them with PostGIS functions; then use pgsql2shp to export the clustered trees to a shapefile which tilemaker could load.

[bweinlich]

I'm afraid that computing something like this on the fly with Martin could cost a lot of computing time. As my tiles are hosted inside a public cloud I would like reduce computing time to a minimum.

But your second idea using osm2pgsql in combination with PostGIS & QGIS as frontend should work well as QGIS has a point clusterin feature. Thank you very much!

[bweinlich]

I tried it out and now I have a Shapefile with the trees as point features. I added the layer in the config.json like this:

"tree": { "minzoom": 13, "maxzoom": 14, "source": "/tiles/trees-reduced-shape/trees-reduced.shp", "source_columns": true }

Tile creation works without errors (the shapefile is listed). But now I can't see the trees in the resulting vector tiles anymore. Do I have to reference the layer in the process.lua file? Have I forgotten something?

[systemed]

Is your shapefile in standard lat/long projection (EPSG 4326)?

[bweinlich]

It was in WebMercator. Thankyou, this did the trick. Sry for not looking in the documentation.

[systemed]

No problem - glad it works!

[dieterdreist]

mapbox/tippecanoe can reduce the number of point features according to a density (max number in tile)

[bweinlich]

Can tippecanoe also process osm.pbf files as input like tilemaker? Or do I need a preprocessing here?

I think I will use PostGIS & QGIS because I am more flexible with it. Nevertheless many thanks for your idea :)

[dieterdreist]

sent from a phone

On 18 Jun 2023, at 13:46, ToraXaroT ***@***.***> wrote: Can tippecanoe also process osm.pbf files as input like tilemaker? Or do I need a preprocessing here?

afaik only geojson as input.