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Hi: I have a question about the features rendering in osm. 1 Lines For a given feature like a highway, it contains so many nodes, so it would be find to render it in a large zoom level, but I wonder if osm simplify the data when the same feature is rendered in a small zoom level? Since in my opinion render the same number of points in a small zoom have two drawbacks: 1.1 Unnecessary resource consume In a small zoom, the points are too close to another, it would be hardly to different two points by human. But the more the points to be rendered, the more resource will be used. 1.2 The line will seem to be not smooth Since in a certain distance(in pixel), there maybe too many points drawn, so the line may not have a nice look and feel. I wonder how does osm handle this kind of problem,or do I miss anything? |
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The question you are asking applies to rendering, i.e. the drawing of maps from OSM data. There are many different rendering programs out there and most of them are not OSM specific; so your question cannot be answered in general. The specific rendering engine used on the openstreetmap.org web site is called Mapnik and usually works in conjunction with a spatial database; OSM data is imported into the database, and then loaded and drawn. There are three ways how data can be simplified before drawing in this scenario -
Thanks for your reply. In fact, I know mapnik, and I have used it in our project.
While when I post this question, I want to now how does the osm handle this for generating tiles used at
(05 Jun '14, 11:35)
hguser
As written above in point 2: Only for the landmasses. Also see this similar question.
(05 Jun '14, 12:37)
cartinus
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to which renderer or rendering style are you referring to?
Are there any differences between different style? I thought the render mechanism would be the same. :(
Not in answer, but just for info, here is the renderer wiki link http://wiki.openstreetmap.org/wiki/Renderer
Remember that a simplification process also uses resources, so it's not always worth the effort.