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Leaflet Vector Tiles

Leaflet Vector Tiles

An introduction to vector tiles as and Leaflet.MapboxVectorTile

Nicholas Hallahan

October 15, 2014

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  1. “Old School” PNG Raster Tiles • Just a grid of

    PNG images that you can slip around… Actual PNG Tile From OpenStreetMap Zoomed In…
  2. Vector Tile No colors at all… It is a bunch

    of arrays in a 256 x 256 matrix. [ (x1,y1), (x2,y2), (x3,y3) …]
  3. Here’s what we would have ! if there are two

    lines in a tile… [ (x1,y1), (x2,y2), (x3,y3) …], [ (x1,y1), (x2,y2), (x3,y3) …]
  4. Same Tile Schema as PNG • Same addressing scheme as

    PNG Tiles • ( Google / OpenStreetMap Schema ) tileurl.com/4/2/5.png tileurl.com/4/2/5.pbf
  5. Specification • Decodes binary protocal buffer (Google) files that adhere

    to the Mapobox Vector Tile (Mapbox) Specification. https://github.com/mapbox/vector-tile-spec
  6. Why not GeoJSON? • A protocal buffer is a binary

    format that is very terse and compact, so it requires much less bandwidth than text-encoded JSON. • It automatically simplifies geometries appropriately to your given zoom level. • You cut out all of the extra data that the renderer never even uses…
  7. What do the values look like? • Data values are

    decoded into pixel coordinates relative to the origin of the tile. • If 2 points are in a pixel, it is automatically simplified into 1 point. • This is in a post-projection space. It is exactly in the correct form for your renderer…
  8. Each tile is a separate HTML5 Canvas. Polygon Framgent 1

    Polygon Framgent 2 of the Democratic Republic of Congo Feature
  9. How does this relate to MapboxGL? • Leaflet.MapboxVectorTile renders vector

    tiles as a set of canvas tile layers in Leaflet. • MapboxGL is more advanced than Leaflet and runs primarily from vector tiles. This uses OpenGL / WebGL instead of HTML5 canvas to render. It is more performant, but it is less stable than Leaflet and does not work on Internet Exploder.
  10. The Spatial Server (formally known as Chubbs)… If you want

    Mapbox to serve it, you need to pre-render your tiles into .mbtiles format… SpatialServer looks at PostGIS tables and cuts you tiles on the fly!