Tuesday, November 03, 2009

New OGC WMTS hits the street - supporting REST interfaces

CubeWerx is in the process of launching its OGC WMTS implementation and the feature list is impressive - tiles created using OGC Styled Layer Descriptor (SLD), multiple tile sets from the same data (to respond to different symbology or map projection requirements), no database needed to deploy, REST interfaces and more.

With the recent release of a proposed standard for tile-based web mapping, Web Map Tile Service (WMTS), the OGC and members like CubeWerx are poised to provide open alternatives for "slippy" tile-based web mapping. Worked on quietly by the gurus at CubeWerx, CREAF and the Autonomous University of Barcelona - the candidate WMTS Interface Standard is much like OGC's popular WMS, but it enables faster server performance.

As many know, OGC Web Map Server (WMS) has been criticized for being slow because it creates a new image for each request – rather than returning pre-generated tiles that provide an almost instant zoom and pan. WMS was designed this way because there were two goals behind the interface, interoperability and the ability to overlay many sources - and in this respect it's been very successful. A WMS client can overlay map layers from many sources in an arbitrary bounding box at an arbitrary scale with any number of styles. But this flexibility comes at a price - since a WMS server is required to generate each requested map image on the fly it's slower to respond than a tile map service.

But OGC WMTS like CubeSERV Web Map Tile Server (WMTS) change all this. To improve performance, instead of creating a new image for each request, the WMTS returns small pre-generated images (e.g., PNG or JPEG) or reuses identical previous requests that follow a set of tile matrices. This service is also the first OGC standard to include a RESTful approach in addition to the usual OGC "KVP" encodings. The "oh, that makes sense" aspect of WMTS has already resulted in implementation in clients like Gaia 3.4.

Bottom Line - WMTS provides a natural way to evolve WMS services into a more constrained - but more scalable and faster service - so anyone can build services and applications that are fast, easy to use, and democratically accessible.

- Jeff


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