How does Polymaps compare to OpenLayers?

The linked answer (Cai's) provides a pretty great high-level overview of the differences.

In more low-level terms, OpenLayers is an older library that is pretty heavy (… is 854kb), but is pretty cross platform, while Polymaps is extremely light ( is 30kb).

OpenLayers also supports IE, while Polymaps, due to being reliant on SVG, does not (until IE9). OpenLayers supports OpenGIS formats while Polymaps leverages GeoJSON quite heavilty. Which is to say, OpenLayers is the older workhorse, and Polymaps is the younger, faster, meaner entry.

2 Replies to “How does Polymaps compare to OpenLayers?”

  1. I found that the Polymaps documentation ( has an explanation of the difference:

    Most mapping libraries focus on 256×256-pixel image tiles, with only limited support for dynamic overlays such as county boundaries and point clouds. These libraries assume that data needed to produce the desired overlay can be loaded into memory all-at-once, making it difficult to visualize large datasets. Furthermore, while image tiles automatically adjust in resolution as the map zooms in or out, the overlay resolution remains constant; this greatly limits multi-scale exploration of data, as the resolution must be fixed either for macro- (e.g., state-level) or micro- (e.g., block-level) observation.

    The goal of Polymaps is to better support rich, large-scale data overlays on interactive maps by extending the tile metaphor to vector graphics: in addition to standard image tiles, Polymaps supports vector tiles that are rendered with SVG. The vector geometry is loaded as GeoJSON via asynchronous XMLHttpRequest; Point geometry objects are rendered as SVG circle elements, Polygonss as paths, and so on. By loading geometry at known tile boundaries, requests can be issued efficiently on-demand by the client, and responses trivially cached on the server. When the user zooms in, geometry can be seamlessly refined to show greater detail, while on zoom out, geometry can be simplified to improve performance.

  2. a main difference that I've found is that polymaps is a (actually amazing) 'overlays' library to use for google/like webgis, where you need to show your data and add maybe some markers.
    openlayers is a true webgis library, that additionally contains core components for vector editing, polygon splitting, snapping, wfs publishing and many more.
    so, if you need a 'googlemaps replacement', both polymaps and openlayers can be useful, and maybe polymaps can offer a better user experience, but if you need to build a webgis, actually you must use openlayers.

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