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Generalization project started

06 September 2022

OpenStreetMap has quite a lot of very detailed geodata. That’s great for generating very detailed maps. But it is sometimes not so easy to create overview maps in smaller map scales and for smaller zoom levels. We can’t see the forest for all the trees.

To solve this a cartographer uses a bunch of techniques, collectively called generalization: You leave out some details, merge several smaller things into a bigger one, or smooth lines that seem overly wiggely when viewed from afar. There are many more of these techniques.

When generating maps automatically based on osm2pgsql we usually use SQL queries after importing the data, either in some steps after import, or when using the data, for instance when rendering tiles. This is not simple to do and often slow because of the complex processing involved. And if you want to update your database with changes from OSM you have to figure out how to only update what’s needed.

With all these problems, osm2pgsql could lend a helping hand. This is what the generalization project is all about. We want to implement some of that functionality in osm2pgsql and also make it easier to access the functionality that the PostgreSQL/PostGIS database already has through osm2pgsql.

Thanks to the Prototype Fund and the German Federal Ministry of Education and Research we got a research grant to work on this project for half a year starting from now, September 2022. See this issue for some of the details we’ll be working on.