<HTML><HEAD>
<META content="text/html; charset=iso-8859-1" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 10.00.9200.17183"></HEAD>
<BODY style="FONT: 10pt Tahoma; MARGIN: 4px 4px 1px">
<DIV>Hi Mike, hi François, hi all,</DIV>
<DIV> </DIV>
<DIV>I don't find the "length=*" tag redundant either for linear objects like streetlines, especially in the case of pretty steep ones: as they're projected for mapping purposes from 3D to 2D, their actual length is not the one you measure on the map but you should consider dividing it by cosinus(A) where A is the angle of inclination between the local horizontal plan and the linear feature. Pythagore said it, man ;-)</DIV>
<DIV>E.g.: a 17-degree mapped mountain road or San Francisco street's will get its actual length a 5% bonus compared to its real-life counterpart. Pick a 100-meter-or-more road, it's not just a bunch of cm. Depends on the accuracy you need, mostly for analysis purposes.</DIV>
<DIV> </DIV>
<DIV><A href="http://en.wikipedia.org/wiki/Grade_%28slope%29">http://en.wikipedia.org/wiki/Grade_%28slope%29</A></DIV>
<DIV><A href="http://www.datapointed.net/visualizations/maps/san-francisco/streets-slope/">http://www.datapointed.net/visualizations/maps/san-francisco/streets-slope/</A></DIV>
<DIV> </DIV>
<DIV>My 2c,</DIV>
<DIV> </DIV>
<DIV>- Yann</DIV>
<DIV><BR><BR>>>> <A href="mailto:tagging-request@openstreetmap.org> 27/01/2015 16:15 >>">tagging-request@openstreetmap.org> 27/01/2015 16:15 >></A><BR></DIV>
<DIV>Date: Tue, 27 Jan 2015 16:13:17 +0100<BR>From: François Lacombe <fl.infosreseaux@gmail.com><BR>To: "Tag discussion, strategy and related tools"<BR> <tagging@openstreetmap.org><BR>Subject: Re: [Tagging] length=<BR>Message-ID:<BR> <CAG0ygLdXgbC+Oe2gLoYzdhcg6QxJaozhCgZPBH9Dh7sNttDOkA@mail.gmail.com><BR>Content-Type: text/plain; charset="utf-8"<BR><BR>Hi Mike,<BR><BR>I don't find it redundant since the length=* tag can give the real length<BR>of a feature.<BR>The way in OSM is only a (sometimes not precise) drawing of an existing<BR>feature and can be different from the reality.<BR><BR>The wiki can be completed with such a nuance.<BR><BR>I personally recommend to use the length key while mapping street cabinets<BR>as nodes.<BR><A href="http://wiki.openstreetmap.org/wiki/Tag:man_made%3Dstreet_cabinet">http://wiki.openstreetmap.org/wiki/Tag:man_made%3Dstreet_cabinet</A><BR><BR>All the best<BR><BR>*François Lacombe*<BR><BR>fl dot infosreseaux At gmail dot com<BR>www.infos-reseaux.com<BR>@InfosReseaux <<A href="http://www.twitter.com/InfosReseaux">http://www.twitter.com/InfosReseaux</A>><BR><BR>2015-01-27 16:04 GMT+01:00 Mike Thompson <miketho16@gmail.com>:<BR><BR>> I have noticed a "length" tag used on some linear ways [1]. It seems<BR>> that this is redundant, as the length could be calculated from the<BR>> geometry itself. It could also be the source of future errors should<BR>> someone split the way, for example to add more detailed tagging, such<BR>> as varying smoothness.<BR>><BR>> The length key does have a wiki page [2], but the page doesn't have<BR>> much content. Perhaps it is only intended for nodes?<BR>><BR>> What do you think? Should the length tag be used with ways and<BR>> relations where the length can be calculated from the geometry itself?<BR>> Am I missing something?<BR>><BR>> MIke<BR>><BR>> [1] <A href="https://www.openstreetmap.org/way/324078614">https://www.openstreetmap.org/way/324078614</A><BR>> [2] <A href="http://wiki.openstreetmap.org/wiki/Key:length">http://wiki.openstreetmap.org/wiki/Key:length</A><BR>><BR></DIV></BODY></HTML>