Hi Sandor, Is any of this work open source, or have open specifications on the web? Statements like comparisons between filesizes of raster & vector data need to be cited.
Tom On Fri, May 25, 2012 at 8:44 AM, Sandor Seres <[email protected]> wrote: > Scale/zoom levels and tiling are essential for mapping servers, especially > if pretending on streaming transmission model. In case of a > vector/parametric data transmission service the scale levels’ generation > and the tiling of these, as a rule, is performed in quite a different way > compared to the traditional raster format based service (keep in mind that > a well constructed vector format may 20 – 40 TIMES be smaller than the > corresponding PNG raster format for the same content). We do an OSM vector > transmission based service for mobile apps (see www.fasterimaging.com). > > As someone properly emphasized a clipping is essential for any vector > tiling. But, while clipping of line-work objects (roads, streets, borders > …) is rather trivial, clipping of area objects is somewhat more complex and > complicated issue. Besides the clipping, some kind of area > reconstruction/restructuring has to be done (one container area may be > clipped into many parts, the same with the corresponding holes, the > restructuring has to decide which new holes are in which new areas, than > the issue of trivial tiles or empty tiles and tiles inside areas and so > on). Also, tiling inevitably results in a considerably larger data amount > compared to the original dataset. So, the question is – is it possible to > provide a server that combines the tiling’s efficiency and the data size at > certain, close to optimal, level. Fortunately, latest research and an > experimental version of such a server show that the answer is yes. The > experiments are performed on OSM vector data for Europe from some weeks ago > (Roughly 30 object classes/layers, 12 area classes like rivers, lakes, > forests, sea …, 12 line-work classes like roads, streets, paths, water > lines … and some point object classes. POIs and LBSs are overlays on such a > base map). The estimates also show that such a very simple server (no DB, > no caching …) is fully realistic with extraordinary performance (respond to > tens of thousands requests per second) and scalability (just make a new > copy as needed). > > A white paper, describing in more details the above subject, is > available. Though in bullets format with many illustrations and with a > working title – Hybrid data format, multi tiling and a new server model. > Interested? > Sandor > _______________________________________________ > dev mailing list > [email protected] > http://lists.openstreetmap.org/listinfo/dev > >
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