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reworked landcover layer (#1035)

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Instead of using [Douglas-Peucker algorithm](https://postgis.net/docs/ST_SimplifyPreserveTopology.html) which is using for generalized tables [imposm](https://imposm.org/docs/imposm3/latest/mapping.html#generalized-tables) it is used [Visvalingam-Whyatt algorithm](https://postgis.net/docs/ST_SimplifyVW.html).

Solution:
remove imposm generalized tables (during `import-osm`) and create generalization in `import-sql` step for zooms 7-14. Zooms 0-6 are from Natural Earth data.

Upper zoom levels (7 and 8) are ok to merge with no big impact on creation speed. In Canada from z9 it took too long. Between zoom levels 10 - 13 there can be union polygons with less than 300 edge points (empirical number based on a test on Canada forest, can be discussed). Polygons with more than 300 edge points are just simplified. Zoom 14 is from the original dataset `osm_landcover_polygon`.

There is also removed `osm_id` which is never used and not passed into vector tiles.
This commit is contained in:
Tomas Pohanka
2020-11-11 15:11:48 +02:00
committed by GitHub
parent 0dc8c3256c
commit 4a1b0afa26
5 changed files with 322 additions and 138 deletions
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135
layers/landcover/landcover.sql
View File

@@ -21,168 +21,121 @@ $$ LANGUAGE SQL IMMUTABLE
-- etldoc: ne_110m_glaciated_areas -> landcover_z0
CREATE OR REPLACE VIEW landcover_z0 AS
(
SELECT NULL::bigint AS osm_id, geometry, 'glacier'::text AS subclass
SELECT geometry, 'glacier'::text AS subclass
FROM ne_110m_glaciated_areas
);
CREATE OR REPLACE VIEW landcover_z2 AS
(
-- etldoc: ne_50m_glaciated_areas -> landcover_z2
SELECT NULL::bigint AS osm_id, geometry, 'glacier'::text AS subclass
SELECT geometry, 'glacier'::text AS subclass
FROM ne_50m_glaciated_areas
UNION ALL
-- etldoc: ne_50m_antarctic_ice_shelves_polys -> landcover_z2
SELECT NULL::bigint AS osm_id, geometry, 'ice_shelf'::text AS subclass
SELECT geometry, 'ice_shelf'::text AS subclass
FROM ne_50m_antarctic_ice_shelves_polys
);
CREATE OR REPLACE VIEW landcover_z5 AS
(
-- etldoc: ne_10m_glaciated_areas -> landcover_z5
SELECT NULL::bigint AS osm_id, geometry, 'glacier'::text AS subclass
SELECT geometry, 'glacier'::text AS subclass
FROM ne_10m_glaciated_areas
UNION ALL
-- etldoc: ne_10m_antarctic_ice_shelves_polys -> landcover_z5
SELECT NULL::bigint AS osm_id, geometry, 'ice_shelf'::text AS subclass
SELECT geometry, 'ice_shelf'::text AS subclass
FROM ne_10m_antarctic_ice_shelves_polys
);
CREATE OR REPLACE VIEW landcover_z7 AS
(
-- etldoc: osm_landcover_polygon_gen7 -> landcover_z7
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen7
);
CREATE OR REPLACE VIEW landcover_z8 AS
(
-- etldoc: osm_landcover_polygon_gen6 -> landcover_z8
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen6
);
CREATE OR REPLACE VIEW landcover_z9 AS
(
-- etldoc: osm_landcover_polygon_gen5 -> landcover_z9
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen5
);
CREATE OR REPLACE VIEW landcover_z10 AS
(
-- etldoc: osm_landcover_polygon_gen4 -> landcover_z10
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen4
);
CREATE OR REPLACE VIEW landcover_z11 AS
(
-- etldoc: osm_landcover_polygon_gen3 -> landcover_z11
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen3
);
CREATE OR REPLACE VIEW landcover_z12 AS
(
-- etldoc: osm_landcover_polygon_gen2 -> landcover_z12
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen2
);
CREATE OR REPLACE VIEW landcover_z13 AS
(
-- etldoc: osm_landcover_polygon_gen1 -> landcover_z13
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon_gen1
);
CREATE OR REPLACE VIEW landcover_z14 AS
(
-- etldoc: osm_landcover_polygon -> landcover_z14
SELECT osm_id, geometry, subclass
FROM osm_landcover_polygon
);
-- etldoc: layer_landcover[shape=record fillcolor=lightpink, style="rounded, filled", label="layer_landcover | <z0_1> z0-z1 | <z2_4> z2-z4 | <z5_6> z5-z6 |<z7> z7 |<z8> z8 |<z9> z9 |<z10> z10 |<z11> z11 |<z12> z12|<z13> z13|<z14_> z14+" ] ;
CREATE OR REPLACE FUNCTION layer_landcover(bbox geometry, zoom_level int)
RETURNS TABLE
(
osm_id bigint,
geometry geometry,
class text,
subclass text
)
AS
$$
SELECT osm_id,
geometry,
SELECT geometry,
landcover_class(subclass) AS class,
subclass
FROM (
-- etldoc: landcover_z0 -> layer_landcover:z0_1
SELECT *
SELECT geometry,
subclass
FROM landcover_z0
WHERE zoom_level BETWEEN 0 AND 1
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z2 -> layer_landcover:z2_4
SELECT *
SELECT geometry,
subclass
FROM landcover_z2
WHERE zoom_level BETWEEN 2 AND 4
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z5 -> layer_landcover:z5_6
SELECT *
SELECT geometry,
subclass
FROM landcover_z5
WHERE zoom_level BETWEEN 5 AND 6
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z7 -> layer_landcover:z7
SELECT *
FROM landcover_z7
-- etldoc: osm_landcover_gen_z7 -> layer_landcover:z7
SELECT geometry,
subclass
FROM osm_landcover_gen_z7
WHERE zoom_level = 7
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z8 -> layer_landcover:z8
SELECT *
FROM landcover_z8
-- etldoc: osm_landcover_gen_z8 -> layer_landcover:z8
SELECT geometry,
subclass
FROM osm_landcover_gen_z8
WHERE zoom_level = 8
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z9 -> layer_landcover:z9
SELECT *
FROM landcover_z9
-- etldoc: osm_landcover_gen_z9 -> layer_landcover:z9
SELECT geometry,
subclass
FROM osm_landcover_gen_z9
WHERE zoom_level = 9
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z10 -> layer_landcover:z10
SELECT *
FROM landcover_z10
-- etldoc: osm_landcover_gen_z10 -> layer_landcover:z10
SELECT geometry,
subclass
FROM osm_landcover_gen_z10
WHERE zoom_level = 10
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z11 -> layer_landcover:z11
SELECT *
FROM landcover_z11
-- etldoc: osm_landcover_gen_z11 -> layer_landcover:z11
SELECT geometry,
subclass
FROM osm_landcover_gen_z11
WHERE zoom_level = 11
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z12 -> layer_landcover:z12
SELECT *
FROM landcover_z12
-- etldoc: osm_landcover_gen_z12 -> layer_landcover:z12
SELECT geometry,
subclass
FROM osm_landcover_gen_z12
WHERE zoom_level = 12
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z13 -> layer_landcover:z13
SELECT *
FROM landcover_z13
-- etldoc: osm_landcover_gen_z13 -> layer_landcover:z13
SELECT geometry,
subclass
FROM osm_landcover_gen_z13
WHERE zoom_level = 13
AND geometry && bbox
UNION ALL
-- etldoc: landcover_z14 -> layer_landcover:z14_
SELECT *
FROM landcover_z14
-- etldoc: osm_landcover_polygon -> layer_landcover:z14_
SELECT geometry,
subclass
FROM osm_landcover_polygon
WHERE zoom_level >= 14
AND geometry && bbox
) AS zoom_levels;