[Routing] Routing web-services?

Robert (Jamie) Munro rjmunro at arjam.net
Tue Nov 20 16:57:13 GMT 2007


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OJW wrote:
> It seems that long-distance driving is something that you normally plan in 
> advance.  So before leaving you can go within range of a wifi hotspot and 
> download your route from the OSM routing server.  
> 
> (While you're there, you download all the map images in a 10km corridor along 
> that route, to help you find your way around)

<rant>

Please can we stop this!

PNG Map tiles are a hack because Internet Explorer can't to SVGs. They
are not supposed to be downloaded and used off line.

In all off-line cases, we should be downloading vectors and drawing the
map on the client. They are much smaller, and they can be scaled,
rotated and 3d projected, while keeping the text facing in a sensible
direction. They can have any elements hidden or displayed, then can be
directly routed over without needing another set of data.

> The mobile devices can still grab vector data for the cities you go through, 
> so that you can find your way around one-way systems, get past closed roads 
> and missed junctions, etc.   Once you're out of the city, you can go back to 
> following the preprepared route.

The devices should just grab vector data for your 10km corridor, if they
are really short of memory, but with reasonable compression (including
lossy compression i.e. removing unneeded data), they shuold be able to
grab more like a whole countries worth of data.

> If you encounter a real problem (your inter-city route isn't available), then 
> you could phone the routing server to get new directions, which would just be 
> a few KB of data for the route, rather than all the data you'd need to plan 
> it yourself.

The data to plan the route yourself is a lot less than the data of the
tiles to follow the route you get from elsewhere.

Let's work on embedding Mapnik, or improving the rendering of Gosmore
and porting it to mobile platforms, or making j2me based vector
renderers for phones, let's stop downloading tiles.

</rant>

Robert (Jamie) Munro
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