Craig Wallace wrote on 25/08/2010 22:28:
On Wed, 25 Aug 2010 20:41 +0100, "Ian Spencer" <ianmspen...@gmail.com> wrote:I think "already by definition cycle-legal" is the very point I am querying. The trouble with the Bicycle restrictions section is that it falls at the first hurdle as nobody seems to have defined (on an international basis remember) whether the use of trunk implies bicycle=yes or no. I wouldn't want to cycle on the A42 (perceived as a motorway), I have cycled along dual carriageways around Redditch which are the same in OSM but quite different in quality. The problems of an administrative definition rather than a "on the ground" definition even though unless there is explicit sign-age there is a legal right.This page defines the default access tags for each highway type in a number of countries: http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions Though its currently lacking a section for the UK. I think the UK should be much the same as the global defaults, at least for the roads. The paths/bridleways/cycleways should be a bit different from the defaults, as access on foot is usually allowed on all of these. It should probably also be different for Scotland vs England & Wales etc due to the rather different the access laws. Though I don't know if there is any maps / routing software using these defined defaults anyway. Also, i think there are a few roads in the UK where cycling is banned, but they haven't been tagged as such (eg parts of the Edinburgh bypass?). I think it would be helpful if something like OpenCycleMap highlighted roads tagged with bicycle=no - it would make the missing bits more obvious, and might encourage people to map more of them. Craig If there are defaults defined with the authority of the project behind it, then Mr Velo or other people deriving software from the project would have something to abide by and would have to put function in to deal with it. When it is undefined, there is not a sensible discussion to have. However, I could point Mr Velo to the variations that are defined which would then mean that he could implement a system for routing appropriately by country. However, if we consider the change across a European border (my geography is challenged, but picking an example I saw, Turkey has a definition that defined trunk roads as defaulting to cycle accessible and Germany has an override that trunk roads are not accessible, with a global default that trunk roads are accessible). If we pretended that Germany had a border with Turkey (pretend I am an American for European geographical purposes!) then how would the programmer using OSM data know what country a road was in? In Velomap's case, he is taking what he knows of how Garmin routing software works and altering the characteristics of the generated maps based on tags in OSM to the attributes of the routes in the Garmin. The Garmin does not understand country borders, the attributes are assumed to be set. So the Velomap translation would have to understand what country any way was in to work out what the OSM attributes really are so they can be mapped appropriately to Garmin. More generally, every routing software based on OSM needs to understand how to map the tags to known routing attributes, and as it stands it is not well defined and means that currently no software based on OSM source can be properly designed to work internationally. It would be easy to amend the editors to always apply default tags for cycling, walking and other issues and allow the editor to set these values depending on circumstance (or allow e.g. potlatch to have country configuration to apply appropriate defaults). The presumption of defaults (e.g. highway=foot might or might not mean "public footpath" in the legal sense) means that the data in OSM is unsound. If I were designing a database for business use I'd want any such presumption defined in stone if I was writing software that relied on it - either these things should be bottomed out, or they should not be relied on and everything should be explicitly tagged. Spenny |
_______________________________________________ Talk-GB mailing list Talk-GB@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-gb
