nacis cartography for a changing map

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)