<br>I apologise for editing too soon and having taken silence as agreement. I will not any more editing of maxspeed while we resolve this issue.<br><br>In my defense I would note again that a considerable percentage of
unrestricted roads in the UK had already been tagged in numeric format and that my
manual edits were about improving consistency rather than going against the majority or even a large minority.<br>
<br>Personally I don't care as much about which standard we adopt as to the idea that we have a preferred format that is documented and is compatible with other countries schemes and which is readily available for routers to use and is implemented! Mot people will hold off mapping speed limits until this is resolved.<br>
<br>If we use the 'national' approach then in my opinion routers must have simple unambiguous access the relevant numeric speed which can either be included in the maxspeed field or in some suitable supporting field. If we use a supporting field then we need some useful defaults. In either case we need to agree which we prefer and what the text is for single carriageway, dual carriageway and motorway.<br>
<br><br><br>Regards,<br><br><br>Peter<br><br><br><br><div class="gmail_quote">On 12 April 2011 11:22, Jerry Clough : SK53 on OSM <span dir="ltr"><<a href="mailto:SK53_osm@yahoo.co.uk">SK53_osm@yahoo.co.uk</a>></span> wrote:<br>
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<div bgcolor="#ffffff" text="#000000"><div class="im">
On 12/04/2011 09:38, Peter Miller wrote:
</div><div><div></div><div class="h5"><blockquote type="cite"><br>
<br>
<div class="gmail_quote">On 11 April 2011 23:39, SomeoneElse <span dir="ltr"><<a href="mailto:lists@mail.atownsend.org.uk" target="_blank">lists@mail.atownsend.org.uk</a>></span>
wrote:<br>
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<div> <br>
On 9 April 2011 08:15, Peter Miller <<a href="mailto:peter.miller@itoworld.com" target="_blank">peter.miller@itoworld.com</a>
<mailto:<a href="mailto:peter.miller@itoworld.com" target="_blank">peter.miller@itoworld.com</a>>>
wrote:<br>
<br>
<br>
</div>
...<br>
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<div>
<div>
<div><br>
We seem to be nudging towards something
close to a conclusion.<br>
<br>
Can I suggest that the following two
methods are valid, however<br>
the second one should be considered to be
'better' and where it is<br>
used then it should be retained to avoid
edit warring.<br>
<br>
</div>
...<br>
</div>
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<div>
<div> Method 2<br>
maxspeed=60 mph<br>
</div>
maxspeed:type=GB:rural<br>
source:maxspeed=survey<br>
<br>
</div>
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<br>
Great - someone has now changed a bunch of
"maxspeed=national" locally to me to to "maxspeed=60 mph".
Next I guess someone will come along and add
"source:maxspeed=i_was_sat_in_my_armchair_and_it_seemed_like_a_good_idea"
or similar? <br>
<br>
We've lost the information that the sign is actually NOT a
60 mph sign. Something like method 2 above would have
avoided losing information (although "GB:rural" is
meaningless; if pushed, "GB:national" or some variant would
be better).<br>
</div>
</blockquote>
<div><br>
The general conclusion of the discussion above was that where
maxspeed=60mph is applied to a single carriageway road there
is also a default 'maxspeed:type=GB:unrestricted' (or whatever
value is decided on). This default (and the one for 70mph for
motorways and dual-carriageways) was including to avoid
burdening the mapper with another tag to add in most
situations. The only 60 mph signs that need another tag are
those rare cases where a single carriageway road does have a
numeric speed limit.<br>
<br>
Fyi, about 95% of currently mapped speed limits in GB at
speeds of 60mph and 70mph speed limits were already tagged as
'maxspeed=60' and 'maxspeed=70' when I first looked at this
about 4 weeks ago leaving only about 5% tagged as national or
nsl.<br>
<br>
I have been converting this remaining 5% over the past 2 weeks
(with a brief delay while we discussed the principle on
talk-gb after a reversion of one of my edits). I have had no
complaints from others to my changes and only one reversion of
one section of the A1 as I mentioned in my post. I take this
as broad support for the changes.<br>
<br>
By tomorrow there will be next to no remaining 'national' and
'nls' speed limits in Britain other than in your patch around
Macclesfied which I won't touch any more.<br>
<br>
There are also a small number (another 5%) of roads that are
not in a recognised mph format, either because the mph is
missing or because it is in km/h or for some other reason. I
will be doing a copy-edit pass on these either fixing them if
it is obvious or marking them with a fixme:maxspeed tag if
not. I should be finished with that in about a week.<br>
<br>
<br>
<br>
Regards,<br>
<br>
<br>
<br>
Peter<br>
<br>
<br>
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Cheers,<br>
Andy<br>
<br>
</div>
<br>
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<br>
</blockquote>
</div>
<br>
<pre><fieldset></fieldset>
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</pre>
</blockquote></div></div>
I think there has been a discussion: I'm a bit surprised that there
was also an agreed consensus, let along one which justifies mass
edits. And if pushed I would have said that the consensus was
maxspeed=national. <br>
<br>
The discussion never pursued a number of outstanding issues. The
most important of these being whether it would be useful to identify
dual carriageways in general, rather than specifically for
identifying speed limits (I believe that it would, the
post-processing effort is high and there are sufficient anamolies to
make it difficult to identify all satisfactorily). Others relate to
relevant speed limits for different classes of vehicles, and finding
suitable names for the additional tags.<br>
<br>
I was unhappy with the original mass edits which added unnecessary
fixme tags and other curious tags to roads. To compound this with
assuming that further mass edits would be acceptable seems way over
the top.<br>
<br>
Suitable renders make a big difference by showing what is missing
and encouraging people to be more proactive in mapping them. Andy
Allan's new experiemental transport layer is a big bonus in that
regard. Using such a render to drive tagging is less desirable,
simply because it results in 'tagging for the renderer' type
behaviour such as the creation of ways to supress display in the ITO
OSM Analysis layer.<br>
<br>
I've not pitched my oar in until now. I had been quite happily using
a numeric value for maxspeed, but the discussion on this list showed
me the error of my ways. The main reason I'd used a value was a
misguided belief that it would improve the times calculated by
routers. I've been playing around with various OSM based routers,
and they dont seem to make sophisticated use of this information. My
impression is that most place speeds into buckets, and that they
make assumptions along the lines of JOSM that a trunk is equivalent
to a dual carriageway motorroad. <br>
<br>
My summary of what seemed sensible would be:<br>
<br>
maxspeed=national or maxspeed=gb:national /* with former
preferred */<br>
dual_carriageway=yes (or something similar) /* preferred over
variants which just refer to speed */<br>
national=70 mph (or variants on this) /*
xxx:type=* tags are horribly ambigous */<br>
source:maxspeed=survey /* don't
change the meaning of the source namespace */<br>
<br>
It is important to keep the basic tagging required as simple as
possible, maxspeed=national can be added as a preset to things like
Potlatch with the appropriate sign. The need to add several
additional tags, adjectival tagging, namespacing should be just
that: optional not essential in tagging. Outside of people who write
programs, who knows what a namespace is?<br>
<br>
Like it or not OSM tagging will always result in inconsistent values
for attributes. Inisisting on a data type for tags has in the past
resulted in horrors like maxspeed=80.467.<br>
<br>
Lastly, never assume that absence of messages is approval or
acquiescence. It is always best to follow up, with "in a few days
time I plan to perform edits x, y, z: please let me know if you have
objections". Then do edits in a limited area, to see if you get
further objections (in this case you have Andy & Steve raising
issues). <br>
<br>
I recently became aware that the Data Working Group have a draft
policy in this area: <a href="http://wiki.openstreetmap.org/wiki/Data_working_group/Mechanical_Edit_Policy" target="_blank">http://wiki.openstreetmap.org/wiki/Data_working_group/Mechanical_Edit_Policy</a>.
<br>
<br>
Jerry<br>
</div>
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<br></blockquote></div><br>