4a1b0afa26
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.
81 lines
2.5 KiB
YAML
81 lines
2.5 KiB
YAML
layer:
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id: "landcover"
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description: |
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Landcover is used to describe the physical material at the surface of the earth. At lower zoom levels this is
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from Natural Earth data for glaciers and ice shelves and at higher zoom levels the landcover is [implied by OSM tags](http://wiki.openstreetmap.org/wiki/Landcover). The most common use case for this layer
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is to style wood (`class=wood`) and grass (`class=grass`) areas.
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buffer_size: 4
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fields:
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class:
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description: |
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Use the **class** to assign natural colors for **landcover**.
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values:
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farmland:
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subclass: ['farmland', 'farm', 'orchard', 'vineyard', 'plant_nursery']
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ice:
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subclass: ['glacier', 'ice_shelf']
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wood:
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subclass: ['wood', 'forest']
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rock:
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subclass: ['bare_rock', 'scree']
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grass:
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subclass: ['fell', 'grassland', 'heath', 'scrub', 'tundra', 'grass', 'meadow', 'allotments', 'park', 'village_green', 'recreation_ground', 'garden', 'golf_course']
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wetland:
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subclass: ['wetland', 'bog', 'swamp', 'wet_meadow', 'marsh', 'reedbed', 'saltern', 'tidalflat', 'saltmarsh', 'mangrove']
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sand:
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subclass: ['beach', 'sand', 'dune']
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subclass:
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description: |
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Use **subclass** to do more precise styling.
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Original value of either the
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[`natural`](http://wiki.openstreetmap.org/wiki/Key:natural),
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[`landuse`](http://wiki.openstreetmap.org/wiki/Key:landuse),
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[`leisure`](http://wiki.openstreetmap.org/wiki/Key:leisure),
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or [`wetland`](http://wiki.openstreetmap.org/wiki/Key:wetland) tag.
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values:
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- allotments
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- bare_rock
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- beach
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- bog
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- dune
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- scrub
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- farm
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- farmland
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- fell
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- forest
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- garden
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- glacier
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- grass
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- grassland
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- golf_course
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- heath
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- mangrove
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- marsh
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- meadow
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- orchard
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- park
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- plant_nursery
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- recreation_ground
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- reedbed
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- saltern
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- saltmarsh
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- sand
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- scree
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- swamp
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- tidalflat
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- tundra
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- village_green
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- vineyard
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- wet_meadow
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- wetland
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- wood
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datasource:
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geometry_field: geometry
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query: (SELECT geometry, class, subclass FROM layer_landcover(!bbox!, z(!scale_denominator!))) AS t
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schema:
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- ./generalized.sql
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- ./landcover.sql
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datasources:
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- type: imposm3
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mapping_file: ./mapping.yaml
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