On Tue, 2011-01-18 at 13:00 +0000, Graham Jones wrote: > I think you are describing what my examples do - for example the map > at http://maps.webhop.net/topo uses a simple base map and the > OpenLayers javascript program running in the web browser draws the > selectable overlays on top of it - the overlays are PNG images with a > transparent background. Or maybe you meant some sort of clever > bitmap with layers defined within it? Whether it is efficient or not > depends on what you are trying to do with the overlays - for single > points (e.g. the power stations themselves on my map) holding bitmaps > is much less efficient than storing the locations of each power > station - you could have OpenLayers take the locations of the points > and plot them.
What you describe is exactly what I meant. Regarding the bitmaps being less efficient, do you have any evidence for this? I mean, naturally there is going to be a trade off between computation and storage, but compression of things like power station points is going to be pretty efficient. It might be that a good compromise would be rasterised layers that use only a single colour per layer (which can be stored incredibly efficiently) with a client-side beautification and overlay step. It would also be very simple then to change the colours of features. cheers, Henry _______________________________________________ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb