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Polymaps is a BSD-licensed display and interaction library for tile-based vector and raster maps using SVG and Javascript.

Our intent is to provide a minimal, extensible, customizable, and free display library for discriminating designers and developers who want to use interactive maps in their own projects. Polymaps provides a core set of features in a tight, clean package, with plenty of hooks for additional functionality.

CAVEATS, FEATURE REQUESTS AND KNOWN BUGS

Browser Support:

• Tested in recent Webkit browsers (Safari 4+, Chrome 6, Webkit nightlies)
• Tested in recent Firefox browsers (3.6+)
• Optimistic about Opera, IE9, but not part of core testing yet.
• SVG is required, even for image display...
  • in other words: if you can't require SVG, don't use Polymaps!

Features:

• Vector overlays in GeoJSON format are supported, both tiled and single file
• Image layers in Google-y spherical mercator format are supported
• There are no default markers or infobubbles (yet?)

API:

• No defensive copying (on input or output).
• No type coercion (e.g., String -> Number for zoom).
• Using == instead of ===.
• Many properties cannot be changed after load (e.g., tile size, URL).
• No (easy) way to lookup a GeoJSON elements by feature id.
• Missing in-code documentation, API reference.
• Include support (not just examples) for TileCache, TileStache, Bing?

Events:

• "move" event does not distinguish zoom / pan / zoom+pan events.
• "show" events are not supported on image tiles.
• There are no corresponding "unload" or "hide" events.
• There is no "error" event if a tile fails to load.
• Arrow control pans three times for two keydowns.

Sizing:

• Maps with no explicit size are auto-resized on window resize;
  • This may miss resize based on DOM changes (e.g., element removal).
  • This may generate spurious resize events for fixed-size parents.
• If the map is bigger than its parent, tiles are not automatically clipped.

Tiles:

• Assumes Mercator projection, with Google-y transform.
• Anti-aliasing artifacts are visible with smooth zooming / rescaled tiles.
• When translucent tiles are rescaled, they can overlap with other resolutions.

Queue:

• Should prioritize tile requests from the center out.
• Create host-specific queues to allow more than 6 simultaneous requests?