Skip to main content

Base schema concepts

Overview​

The Overture base theme includes features desired for rendering a complete basemap. We assign a subtype and class to each feature and pass relevant properties through in the source_tags property. Most of the features in the base theme come from OpenStreetMap via the Daylight Map Distribution.

Feature types​

The base theme has six feature types.

  • bathymetry: topographic representation of underwater areas, e.g. an elevation map of the ocean floor
  • infrastructure: human-made structures such as bridges, towers, pipelines, and airports
  • land: natural land features
  • land_cover: land features derived from satellite imagery, e.g. forest, crop, barren, urban
  • land_use: human-determined land use categories, e.g. residential, agriculture, protected
  • water: natural and human-made water features, includes ocean data derived from the OSM Coastline Tool

Theme concepts​

OpenStreetMap tags to Overture properties​

The subtype and class properties of an infrastructure, land, land_use, and water feature types in the base theme is determined by the original feature's tags on OpenStreetMap.

Below is the logic that is currently used to convert from OSM tags into Overture schema.

tip

Have a suggestion or improvement to the logic? Please start a discussion on Github

How do I interpret this query?

Each WHEN line in the CASE statement is a condition that defines both the subtype and the class of a feature. For example:

WHEN element_at(tags,'highway') = 'bus_stop' THEN ROW('transit', 'bus_stop')

Here, element_at(tags, 'highway') is accessing the value of the highway tag in OSM. So, when highway=bus_stop is present, then the statement returns ROW(subtype, class), in this case, subtype=transit and class=bus_stop.

Since this particular statement is at the top of the list, it will take priority over other tags on the feature. If the same feature was also tagged as an airport gate, those tags would be ignored.

CASE
    -- Railway stations / Subway stations
    WHEN element_at(tags,'railway') IN ('station','halt') THEN CASE
        WHEN element_at(tags,'station') = 'subway' THEN ROW('transit', 'subway_station')
        ELSE ROW('transit', 'railway_' || element_at(tags,'railway'))
    END

    -- Ferry Terminals
    WHEN element_at(tags,'amenity') = 'ferry_terminal' OR (
            element_at(tags,'public_transport') = 'stop_position' AND element_at(tags,'ferry') = 'yes' 
        ) THEN ROW('transit','ferry_terminal')

    -- Transit Stops
    WHEN element_at(tags,'highway') = 'bus_stop' THEN ROW('transit', 'bus_stop')
    WHEN element_at(tags,'route') = 'bus' THEN ROW('transit', 'bus_route')
    WHEN element_at(tags,'amenity') = 'bus_station' THEN ROW('transit', 'bus_station')
    WHEN element_at(tags,'public_transport') IN ('stop_position', 'platform') THEN ROW('transit', element_at(tags,'public_transport'))

    -- Parking
    WHEN element_at(tags,'amenity') IN (
        'parking',
        'parking_space',
        'bicycle_parking',
        'motorcycle_parking'
    ) THEN ROW('transit', element_at(tags,'amenity'))

    -- Aerialways (Linestrings)
    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) = 'ST_LineString' AND element_at(tags,'aerialway') IN (
        'cable_car',
        'chair_lift',
        'drag_lift',
        'gondola',
        'j-bar',
        'magic_carpet',
        'goods',
        'mixed_lift',
        'platter',
        'rope_tow',
        't-bar',
        'zip_line'
    ) THEN ROW('aerialway', element_at(tags,'aerialway'))
    
    -- Pylons are points
    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) = 'ST_Point' AND element_at(tags,'aerialway') = 'pylon' THEN ROW('aerialway', 'pylon')

    -- Stations are nodes/ways
    WHEN element_at(tags,'aerialway') = 'station' THEN ROW('aerialway', 'aerialway_station')

    -- Airports (Polygons)
    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) IN ('ST_Polygon', 'ST_MultiPolygon') AND element_at(tags,'aeroway') IN (
        'airstrip', 
        'apron',
        'helipad',
        'heliport',
        'launchpad',
        'runway',
        'taxiway'
    ) THEN ROW('airport', element_at(tags,'aeroway'))

    -- Airports (LineStrings)
    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) = 'ST_LineString' AND element_at(tags, 'aeroway') IN (
        'runway',
        'stopway',
        'taxilane',
        'taxiway'
    ) THEN ROW('airport', element_at(tags,'aeroway'))

    -- Airports (Points)
    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) = 'ST_Point' AND element_at(tags,'aeroway') IN (
        'airstrip',
        'helipad'
    ) THEN ROW('airport', element_at(tags,'aeroway'))

    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) = 'ST_Point' AND element_at(tags,'aeroway') = 'gate'
        THEN ROW('airport', 'airport_gate')

    WHEN element_at(tags,'aeroway') = 'aerodrome' THEN CASE
        WHEN element_at(tags,'aerodrome:type') = 'military' OR element_at(tags,'landuse') = 'military' OR element_at(tags,'military') IN (
            'airfield'
        ) THEN ROW('airport','military_airport')
        WHEN element_at(tags,'access') IN ('emergency', 'no', 'permissive', 'private')
            OR element_at(tags,'aerodrome:type') = 'private' THEN ROW('airport','private_airport')
        WHEN lower(element_at(tags,'name')) LIKE '%international%' OR element_at(tags,'aerodrome:type') = 'international'
            OR element_at(tags,'aerodrome') = 'international' THEN ROW('airport','international_airport')
        WHEN lower(element_at(tags,'name')) LIKE '%regional%' OR element_at(tags,'aerodrome:type') = 'regional'
            THEN ROW('airport','regional_airport')
        WHEN lower(element_at(tags,'name')) LIKE '%municipal%' THEN ROW('airport','municipal_airport')
        WHEN lower(element_at(tags,'name')) LIKE '%seaplane%' THEN ROW('airport','seaplane_airport')
        WHEN lower(element_at(tags,'name')) LIKE '%heli%' THEN ROW('airport','heliport')
        ELSE ROW('airport','airport')
    END

    -- Bridges
    WHEN element_at(tags,'bridge') IN (
        'aqueduct',
        'boardwalk',
        'cantilever',
        'covered',
        'movable',
        'trestle',
        'viaduct'
    ) THEN ROW('bridge', element_at(tags,'bridge'))
    WHEN element_at(tags,'bridge:support') IS NOT NULL THEN
        ROW('bridge', 'bridge_support')

    -- Communication
    WHEN element_at(tags,'communication:mobile_phone') <> 'no' THEN ROW('communication','mobile_phone_tower')
    WHEN element_at(tags,'communication') IN ('line','pole') THEN ROW('communication','communication_' || element_at(tags,'communication'))
    WHEN element_at(tags,'tower:type') = 'communication' THEN ROW('communication','communication_tower')

    -- Pedestrian
    WHEN element_at(tags,'highway') IS NULL AND element_at(tags,'footway') IN ('crossing') AND 
        ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) IN ('ST_Polygon','ST_MultiPolygon') THEN ROW('pedestrian','pedestrian_crossing')
    WHEN element_at(tags,'tourism') IN ('information', 'viewpoint') THEN ROW('pedestrian', element_at(tags,'tourism'))
    WHEN element_at(tags,'amenity') IN (
        'atm',
        'bench',
        'picnic_table',
        'post_box',
        'toilets',
        'vending_machine'
    ) THEN ROW('pedestrian', element_at(tags,'amenity'))

    -- Manholes
    WHEN element_at(tags,'manhole') IN ('drain', 'sewer') THEN ROW('manhole', element_at(tags,'manhole'))
    WHEN element_at(tags,'manhole') IS NOT NULL THEN ROW('manhole','manhole')

    -- Power
    WHEN element_at(tags,'power') IN (
        'cable_distribution',
        'cable',
        'catenary_mast',
        'connection',
        'generator',
        'heliostat',
        'insulator',
        'minor_line',
        'plant',
        'portal',
        'sub_station',
        'substation',
        'switch',
        'terminal',
        'transformer'
    ) THEN ROW('power', element_at(tags,'power'))

    WHEN element_at(tags,'power') IN ('line', 'pole', 'tower') THEN ROW('power','power_' || element_at(tags,'power'))

    -- Recreation
    WHEN element_at(tags,'tourism') = ('camp_site') AND ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) = 'ST_Point' THEN ROW('recreation','camp_site')

    -- Towers
    WHEN element_at(tags,'tower:type') IN (
        'bell_tower',
        'cooling',
        'defensive',
        'diving',
        'hose',
        'lighting',
        'lightning_protection',
        'minaret',
        'monitoring',
        'observation',
        'radar',
        'siren',
        'watchtower'
    ) THEN ROW('tower', element_at(tags,'tower:type'))

    -- Utility / human made made containers
    WHEN element_at(tags,'man_made') IN (
        'gasometer',
        'pipeline',
        'reservoir_covered',
        'silo',
        'storage_tank', 
        'utility_pole',
        'water_tower'
    ) THEN ROW('utility', element_at(tags,'man_made'))

    -- Waste Management
    WHEN element_at(tags,'amenity') IN(
        'recycling',
        'waste_basket',
        'waste_disposal'
    ) THEN ROW('waste_management',element_at(tags,'amenity'))

    --Water
    WHEN element_at(tags,'man_made') IN ('dam') THEN ROW('water',element_at(tags,'man_made'))
    WHEN element_at(tags,'waterway') IN ('dam','weir') THEN ROW('water', element_at(tags,'waterway'))
    WHEN element_at(tags,'amenity') = ('drinking_water') AND
        (element_at(tags,'drinking_water') IS NULL OR element_at(tags,'drinking_water') <> 'no') AND
        (element_at(tags,'access') IS NULL OR element_at(tags,'access') <> 'private')
        THEN ROW('water', 'drinking_water')
    WHEN element_at(tags,'amenity') IN ('fountain') THEN ROW('water', 'fountain')


    -- Standalone piers
    WHEN element_at(tags,'man_made') IN ('pier') THEN ROW('pier','pier')


    -- Barrier tags are often secondary on other features, so put them last.
    -- Barrier tags that are not allowed on points:
    WHEN ST_GEOMETRYTYPE(ST_GeomFromBinary(geometry)) <> 'ST_Point' AND element_at(tags,'barrier') IN (
        'cable_barrier',
        'city_wall',
        'chain',
        'ditch',
        'fence',
        'guard_rail',
        'handrail',
        'hedge',
        'jersey_barrier',
        'kerb',
        'retaining_wall',
        'wall'
    ) THEN ROW('barrier', element_at(tags,'barrier'))

    -- Points allowed on these types of barriers:
    WHEN element_at(tags,'barrier') IN (
        'block',
        'bollard',
        'border_control',
        'bump_gate',
        'bus_trap',
        'cattle_grid',
        'cycle_barrier',
        'chain',
        'entrance',
        'full-height_turnstile',
        'gate',
        'hampshire_gate',
        'height_restrictor',
        'jersey_barrier',
        'kerb',
        'kissing_gate',
        'lift_gate',
        'planter',
        'sally_port',
        'stile',
        'swing_gate',
        'toll_booth'
    ) THEN ROW('barrier', element_at(tags,'barrier'))
    WHEN element_at(tags,'man_made') IN ('cutline') THEN ROW('barrier','cutline')

    -- If there remains a barrier tag but it's not in the above list:
    WHEN element_at(tags,'barrier') IS NOT NULL THEN ROW('barrier','barrier')

    -- Lower priority generic `bridge` tags
    WHEN element_at(tags,'man_made') = 'bridge' THEN ROW('bridge','bridge')
    WHEN element_at(tags,'bridge') = 'yes' THEN ROW('bridge','bridge')
END

Schema reference​