Sent from my android device so the quoting is crap! -----Original Message----- From: OpenStreetmap HADW <[email protected]> To: [email protected] Sent: Sat, 07 Sep 2013 15:07 Subject: Re: [Talk-GB] Urban Mixed Access Ways and Barriers (restricted to motor vehicles, open to foot)
On 7 September 2013 14:46, Philip Barnes <[email protected]> wrote: > > Streetmaps do tend to be abstractions of the real world, and > openstreetmap ceased to be be a mere streetmap several years ago, and is > a far far better map than a mere streetmap can ever be. The word > streetmap implies urban, cities. OS maps are abstractions even when not dealing with streets. The other problems with micro-mapping are: - the transition between higher and lower levels of abstraction. I have considered mapping certain road areas as areas, because the line approximation loses important information, but, unless a road joins an area perpendicularly, this doesn't work well in the transition region; - with things like sidewalks, there is usually a fixed distance between the two pedestrian ways and the vehicle way, but the current data structure cannot represent that, and the current tooling doesn't support it very well, so if everyone started mapping sidewalks explicitly, there would be big maintenance problems (I've just seen a transition case where a road both has a separate footpath, with cycle access and the road itself is marked as having parallel cycle tracks); - routing software can no longer just operate on a network of edges and nodes, but needs to know that your can normally cross from one sidewalk to the other, at arbitrary places. (currently I have seen explicit footway crossings, where no physical features exists, being inserted to get round this one. Basically, the abstraction is adding value, by showing that the the sidewalks are related. Trying to incorporate all of the conditions relating to the physical structure of the road using just tags would make things almost impossible to understand. With the level of detail becoming available for buildings, adding the footpaths through developments is accepted, and those around the edge add value simply by showing their presence. YES routers need a bit more inteligence, and in cities with barriers between car and pedestrian, things are simple. A 'clever' foot router could be made to recognise that people can walk anywhere in shopping precincts, so why not the area of a footpath/road combination?
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