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| layout | title | published |
|---|---|---|
| page | Database Schema and Layers | true |
Database Schema
The layer schema tries to stay compliant to Mapbox Streets v6 and Mapbox Streets v5. The detailed documentation on which database tables are mapped to which feature classes, can be found in the following sections.
Aeroways, Barriers and Landusages
For some layers linestring and polygon data needs to be mapped into tables. The different geometries are then both rendered as vector linestrings. The landing strips of airports for example might be a linestring or polygon.
Administrative Borders
The administrative area on lower zoom levels is entirely from Natural Earth data. Only at higher zoom levels where details are more important the OSM borders are rendered.
Natural Earth provides data in several generalization levels. The table with highest generalization is used on the lowest zoom levels and on higher zoom levels the less generalized tables.
Roads, Bridges and Tunnels
Roads are split up into normal roads, tunnels and bridges after a
certain zoom level. z_order and layer attributes are used to order
the geometries on the right z axis. Road labels however will always
contain data for tunnels, bridges and normal roads therefore one table
that is filtered into different views at higher zoom levels is the best
approach.
Points of Interest
Most POIs are in fact points, but buildings tagged with POI attributes are often polygons, which is why tables for both points and polygons are created.
The localrank and scalerank of the #poi_label layer are calculated
from the type and area attributes. The address field is pulled
together from the various address attributes on the tables (street,
housenumber, place, city, postcode and country).
Water
Water bodies for lower zoom levels are taken from Natural Earth data while lakes and rivers are from OpenStreetMap. Big rivers often consist out of a water polygons while smaller rivers are only water ways.
Places
Places are names of cities and villages. To calculate the importance of a city the scalerank of the most important cities from Natural Earth data is merged into the OpenStreetMap data set. For places that do not have a scalerank value a dynamic value is calculated based on the population.
