OpenStreetMap data in its raw form is often hard to use. The goal of this site is to give you access to pre-processed OSM data in a convenient form. But we can not create the data in every form that might be needed, so we give you the background information and the software to do it yourself.
Coastlines are recorded in OSM using the tag natural=coastline. Our coastline processing finds all ways with that tag and stitches them together while correcting small errors.
Antarctic icesheets are handled specially: Instead of tagging the ice sheets, the area in the Antarctic that does not contain any ice is tagged. Our processing takes this into account when creating icesheet outlines and polygons.
All the software we base our processing on is Open Source. Feel free to use it, learn from it, and change it.