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Very big +1 for that.<br>
<br>
Moving from implicit tagging to explicit tagging would cause the
size of the database to explode. An alternative approach may be to
have an optimised function available to derive the "jurisdiction" or
"territory" from specific admin boundaries, and hang the
territory-specific defaults off of them somehow. I can imagine that
the admin level will vary by country; in a federal state such as the
USA or Germany there may be rules set at both a central level and a
state level, but the number of states involved is probably low
enough to only do it at a state level and copy the national defaults
down to the states where they may be overridden. This will avoid
needing a hierarchy of jurisdictions. As there are (IIRC) about 250
countries in the world, and the majority are non-federal for these
purposes, there might be perhaps 500 territories involved, each
being a multipolygon with maybe 0.5kb of data for each giving about
250kb of attribute data for the territory lookup.The polygon data
will be quite a bit bigger of course. On the face of it, it sounds
as though it might be doable.<br>
<br>
Colin<br>
<br>
On 26/08/2010 13:26, Ian Spencer wrote:
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Craig Wallace wrote on 25/08/2010 22:28:
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cite="mid:1282771709.15271.1391751587@webmail.messagingengine.com"
type="cite">
<pre wrap="">On Wed, 25 Aug 2010 20:41 +0100, "Ian Spencer" <a moz-do-not-send="true" class="moz-txt-link-rfc2396E" href="mailto:ianmspencer@gmail.com"><ianmspencer@gmail.com></a>
wrote:
</pre>
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<pre wrap="">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.
</pre>
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<pre wrap="">This page defines the default access tags for each highway type in a
number of countries:
<a moz-do-not-send="true" class="moz-txt-link-freetext" href="http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions">http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions</a>
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
</pre>
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<br>
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.<br>
<br>
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? <br>
<br>
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.<br>
<br>
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.<br>
<br>
Spenny <br>
<br>
<br>
<br>
<br>
<pre wrap="">
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