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Cartographyfor a
Changing MapAJ Ashton, MapBox
Global
● All the data OpenStreetMap has to offer, and more
● Multiscale: 20+ Web Mercator zoom levels
● Multiple label language options
Scalable
● Cloud servers that get added and dropped constantly can’t be too “heavy”
● Tiles should load just as fast with 10 users as with 10,000 users
● Apply different styles to the same underlying data
Up to date
● Currently sync with OSM every 5 minutes
● We want this to be even faster
● The world is always changing
Global + Scaleable+ Up to date
A challenging combination
Global + Scaleable+ Up to date
+ Make it look good
Keeping up with OSM
OSM Changes
1.5 millionchanges per day
over 1000changes per minute
http://osmstats.altogetherlost.com
Most changes are small,but some have big
consequences
Cartography for a changing map:
Simple things
Generalize
NormalizationCleaning OSM data for consistency
Cartography for a changing map:
Not-so simple things
aka. Automaticmanual tweaks
City labels
City labels
● Custom list of scaleranks (based on Natural Earth) and label direction hints
● Fuzzy spatial & fuzzy text join function between incoming OSM data + our list
Airport labels/icons
Cartography for a changing map:
Working with tiles
Tiles are small & static256x256 pixels not a lot to work with
Tiles don’t knowabout other tiles
The terrifyingchaos label problem
No perfect solutionsOnly mitigation strategies
Consistent orderingORDER BY scalerank, population DESC,
osm_id
De-duplicate atthe data level
GROUP BY ST_SnapToGrid(geom)