I want to extract the coastline data from .osm dump and store it so that it is suitable for low-scale maps.
For that I need to reduce the number of points in the lines. What algorithms are there for this operation? How does mapnik render this, for example?
I’ve found one simple approach, which is to pick a point and walk along the line, skipping all the points that are closer than a certain distance (depending on the scale). I thought of making an “average point” of those that are near, but I’m not sure this will make sensible results.