Remove bridge/tunnel attributes from tiny bridges (#1283)

This PR now removes bridge/tunnel/ford attributes from the `transportation` layer from sections of bridge/tunnel etc that are too small to be meaningfully visible at a particular zoom level.  This allows those segments to be generalized into geometries along with the surrounding sections of road, thereby dropping lots of useless little pieces of geometry in lower-zoom tiles.

layers/transportation/update_transportation_merge.sql

@@ -7,6 +7,40 @@ DROP TRIGGER IF EXISTS trigger_store_transportation_highway_linestring_gen_z11 O
 DROP TRIGGER IF EXISTS trigger_flag_transportation_z11 ON osm_highway_linestring_gen_z11;
 DROP TRIGGER IF EXISTS trigger_refresh_z11 ON transportation.updates_z11;
 
+-- Determine whether a segment is long enough to have bridge/tunnel attributes
+-- Dropping small brunnel sections allow for generalization as distinct segments get too small
+CREATE OR REPLACE FUNCTION visible_brunnel(g geometry, brunnel boolean, zoom_level integer)
+    RETURNS boolean AS
+$$
+SELECT
+    brunnel AND
+    -- Width of a tile in meters (111,842 is the length of one degree of latitude at the equator in meters)
+    -- 111,842 * 180 / 2^zoom_level
+    --  = 20131560 / POW(2, zoom_level)
+    -- Drop brunnel if length of way < 2% of tile width (less than 3 pixels)
+    ST_Length(g) *
+        COS(RADIANS(ST_Y(ST_Centroid(ST_Transform(g, 4326))))) *
+        POW(2, zoom_level) / 20131560 > 0.02
+$$ LANGUAGE SQL IMMUTABLE LEAKPROOF
+                PARALLEL SAFE;
+
+-- Determine whether a segment is long enough to have layer attributes
+CREATE OR REPLACE FUNCTION visible_layer(g geometry, layer int, zoom_level integer)
+    RETURNS int AS
+$$
+SELECT
+    CASE WHEN
+    -- Width of a tile in meters (111,842 is the length of one degree of latitude at the equator in meters)
+    -- 111,842 * 180 / 2^zoom_level
+    --  = 20131560 / POW(2, zoom_level)
+    -- Drop brunnel if length of way < 2% of tile width (less than 3 pixels)
+    ST_Length(g) *
+        COS(RADIANS(ST_Y(ST_Centroid(ST_Transform(g, 4326))))) *
+        POW(2, zoom_level) / 20131560 > 0.02
+    THEN layer END
+$$ LANGUAGE SQL IMMUTABLE LEAKPROOF
+                PARALLEL SAFE;
+
 -- Instead of using relations to find out the road names we
 -- stitch together the touching ways with the same name
 -- to allow for nice label rendering
@@ -121,7 +155,28 @@ SELECT (ST_Dump(ST_LineMerge(ST_Collect(geometry)))).geom AS geometry,
            ELSE NULL::text END AS access,
        toll,
        layer
-FROM osm_highway_linestring_gen_z11
+FROM (
+    -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
+    SELECT geometry,
+           NULL::bigint AS osm_id,
+           highway,
+           network,
+           construction,
+           visible_brunnel(geometry, is_bridge, 11) AS is_bridge,
+           visible_brunnel(geometry, is_tunnel, 11) AS is_tunnel,
+           visible_brunnel(geometry, is_ford, 11) AS is_ford,
+           expressway,
+           z_order,
+           bicycle,
+           foot,
+           horse,
+           mtb_scale,
+           sac_scale,
+           access,
+           toll,
+           visible_layer(geometry, layer, 11) AS layer
+    FROM osm_highway_linestring_gen_z11
+) osm_highway_linestring_normalized_brunnel_z11
 -- mapping.yaml pre-filter: motorway/trunk/primary/secondary/tertiary, with _link variants, construction, ST_IsValid()
 GROUP BY highway, network, construction, is_bridge, is_tunnel, is_ford, expressway, bicycle, foot, horse, mtb_scale, sac_scale, access, toll, layer
 ;
@@ -163,7 +218,29 @@ BEGIN
         access,
         toll,
         layer
-    FROM osm_transportation_merge_linestring_gen_z11
+    FROM (
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
+        SELECT geometry,
+            id,
+            NULL::bigint AS osm_id,
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 11) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 11) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 11) AS is_ford,
+            expressway,
+            z_order,
+            bicycle,
+            foot,
+            horse,
+            mtb_scale,
+            sac_scale,
+            access,
+            toll,
+            visible_layer(geometry, layer, 11) AS layer
+        FROM osm_transportation_merge_linestring_gen_z11
+    ) osm_highway_linestring_normalized_brunnel_z11
     WHERE (update_id IS NULL OR id = update_id)
         AND highway NOT IN ('tertiary', 'tertiary_link', 'busway', 'bus_guideway')
         AND construction NOT IN ('tertiary', 'tertiary_link', 'busway', 'bus_guideway')
@@ -193,7 +270,29 @@ BEGIN
         access,
         toll,
         layer
-    FROM osm_transportation_merge_linestring_gen_z10
+    FROM (
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
+        SELECT geometry,
+            id,
+            NULL::bigint AS osm_id,
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 10) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 10) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 10) AS is_ford,
+            expressway,
+            z_order,
+            bicycle,
+            foot,
+            horse,
+            mtb_scale,
+            sac_scale,
+            access,
+            toll,
+            visible_layer(geometry, layer, 10) AS layer
+        FROM osm_transportation_merge_linestring_gen_z10
+    ) osm_highway_linestring_normalized_brunnel_z10
     WHERE (update_id IS NULL OR id = update_id)
     ;
 END;
@@ -238,11 +337,24 @@ SELECT ST_Simplify(ST_LineMerge(ST_Collect(geometry)), ZRes(10)) AS geometry,
        is_ford,
        expressway,
        min(z_order) as z_order
-FROM osm_transportation_merge_linestring_gen_z9
+FROM (
-WHERE (highway IN ('motorway', 'trunk', 'primary') OR
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
-       construction IN ('motorway', 'trunk', 'primary'))
+        SELECT geometry,
-       AND ST_IsValid(geometry)
+            osm_id,
-       AND access IS NULL
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 9) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 9) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 9) AS is_ford,
+            expressway,
+            z_order
+        FROM osm_transportation_merge_linestring_gen_z9
+        WHERE (highway IN ('motorway', 'trunk', 'primary') OR
+            construction IN ('motorway', 'trunk', 'primary'))
+            AND ST_IsValid(geometry)
+            AND access IS NULL
+    ) osm_highway_linestring_normalized_brunnel_z9
 GROUP BY highway, network, construction, is_bridge, is_tunnel, is_ford, expressway
 ;
 CREATE INDEX IF NOT EXISTS osm_transportation_merge_linestring_gen_z8_geometry_idx
@@ -280,7 +392,21 @@ BEGIN
         is_ford,
         expressway,
         z_order
-    FROM osm_transportation_merge_linestring_gen_z8
+    FROM (
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
+        SELECT geometry,
+            id,
+            osm_id,
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 8) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 8) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 8) AS is_ford,
+            expressway,
+            z_order
+        FROM osm_transportation_merge_linestring_gen_z8
+    ) osm_highway_linestring_normalized_brunnel_z8
         -- Current view: motorway/trunk/primary
     WHERE
         (update_id IS NULL OR id = update_id) AND
@@ -302,10 +428,26 @@ BEGIN
         is_ford,
         expressway,
         z_order
-    FROM osm_transportation_merge_linestring_gen_z7
+    FROM (
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
+        SELECT geometry,
+            id,
+            osm_id,
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 7) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 7) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 7) AS is_ford,
+            expressway,
+            z_order
+        FROM osm_transportation_merge_linestring_gen_z7
+        WHERE
+            (highway IN ('motorway', 'trunk') OR construction IN ('motorway', 'trunk'))
+    ) osm_highway_linestring_normalized_brunnel_z7
+        -- Current view: motorway/trunk/primary
     WHERE
         (update_id IS NULL OR id = update_id) AND
-        (highway IN ('motorway', 'trunk') OR construction IN ('motorway', 'trunk')) AND
         ST_Length(geometry) > 100;
 
     DELETE FROM osm_transportation_merge_linestring_gen_z5
@@ -324,15 +466,30 @@ BEGIN
         is_ford,
         expressway,
         z_order
-    FROM osm_transportation_merge_linestring_gen_z6
+    FROM (
-    WHERE
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
-        (update_id IS NULL OR id = update_id) AND
+        SELECT geometry,
-        -- Current view: all motorways and trunks of national-importance
+            id,
-        (highway = 'motorway'
+            osm_id,
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 6) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 6) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 6) AS is_ford,
+            expressway,
+            z_order
+        FROM osm_transportation_merge_linestring_gen_z6
+        WHERE
+            (highway = 'motorway'
             OR construction = 'motorway'
             -- Allow trunk roads that are part of a nation's most important route network to show at z4
             OR (highway = 'trunk' AND osm_national_network(network))
-        ) AND
+        )
+    ) osm_highway_linestring_normalized_brunnel_z6
+    WHERE
+        (update_id IS NULL OR id = update_id) AND
+        -- Current view: all motorways and trunks of national-importance
         ST_Length(geometry) > 500;
 
     DELETE FROM osm_transportation_merge_linestring_gen_z4
@@ -351,10 +508,24 @@ BEGIN
         is_ford,
         expressway,
         z_order
-    FROM osm_transportation_merge_linestring_gen_z5
+    FROM (
+        -- Remove bridge/tunnel/ford attributes from short sections of road so they can be merged
+        SELECT geometry,
+            id,
+            osm_id,
+            highway,
+            network,
+            construction,
+            visible_brunnel(geometry, is_bridge, 5) AS is_bridge,
+            visible_brunnel(geometry, is_tunnel, 5) AS is_tunnel,
+            visible_brunnel(geometry, is_ford, 5) AS is_ford,
+            expressway,
+            z_order
+        FROM osm_transportation_merge_linestring_gen_z5
+        WHERE osm_national_network(network)
+    ) osm_highway_linestring_normalized_brunnel_z5
     WHERE
         (update_id IS NULL OR id = update_id) AND
-        osm_national_network(network) AND
         -- Current view: national-importance motorways and trunks
         ST_Length(geometry) > 1000;
 END;