[Tagging] power=* tag: minor_line vs. line

David Marchal penegal at live.fr
Thu Oct 15 12:59:41 UTC 2015

Thanks for the full story, Lauri. I understand now why the subject seems so sensitive to some. I retain from your story, if I correctly understood it that:* the current usage of minor_line/line is the one I previously suggested: use minor_line for lines mainly on poles and line for lines mainly on towers, with a tolerance if a line occasionally uses something different;* the problem of this modelling, which bothers some, is that it leads to a fuzzy modelling from a technical, power network point of view, because it doesn't reflect the actual usage, voltage or any technical characteristics of the power line;* the current usage of minor_line/line is nevertheless retained as it is a perceptible, beginners-friendly distinction, allows easy rendering, and as other essential characteristics, as voltage, number of cables or tower/pole shapes are already managed by other tags, even if some others, as the distribution/transport distinction, isn't modelled.
Am I correct?

> Date: Thu, 15 Oct 2015 13:12:02 +0300
> From: lkytomaa at gmail.com
> To: tagging at openstreetmap.org
> Subject: Re: [Tagging] power=* tag: minor_line vs. line
> David Marchal wrote:
> > I saw conflicting points of view regarding the difference between these two
> > ways for modelling aerial power lines: some say that it is the voltage which
> > matters, others say that it's the visibility difference that matters, others
> Hi.
> To properly understand this issue, here's the history of the tags:
> - originally, in 2006, there was just the page Key:power (then under the
> title "Proposed features/Power Lines") with discussions specifically
> agreeing that the project should use a different tag for "large" lines
> "strung from latticework pylons" and other lines. At that time, nobody had
> seriously thought about ever mapping the smaller ones, and it is a common
> separation on all pre-OSM maps (and their source data). Being a global
> project, "latticework pylons" referred to the type of construction common in
> the countries where the early mappers resided, so even if other countries
> used different constructions for high voltage lines, they would still be
> power=tower. The original description/proposal
> http://wiki.openstreetmap.org/w/index.php?title=Key:power&oldid=6410
> and after discussions agreeing:
> http://wiki.openstreetmap.org/w/index.php?title=Key:power&oldid=17349#Notes
> Power=pole was suggested already in November 2006 for support structures
> smaller than power=tower (in the link above)
> - in July 2007 the descriptions of power=line and power=tower were copied
> to the Map_Features. Still, the assumption and the practice was that people
> didn't map "smaller" power lines at all; even if the description of 'line' only
> referenced "the path of power cables", it was assumed they'd only be drawn
> between power=tower nodes, i.e. only high voltage lines on "big" pylons.
> http://wiki.openstreetmap.org/w/index.php?title=Map_Features&diff=39342&oldid=39308
> - in January 2008 pages were created for
> * Tag:power=tower, with the sentence still present "Should not be used for
> electricity or telephone cables carried on single wooden pole."
> * Tag:power=line, which still had a description referencing "way following
> power cables"
> * Key:power was changed to reference the template Map_features:power,
> with no change in wording
> - In March 2008 some had discussed on the osm talk list that minor
> lines could be mapped with a different tag.
> - following my question in September 2008 on Talk:Key:power, minor_line was
> suggested and others started using it, too, if they hadn't already
> prior to that.
> - in January 2009 the suggestion to use minor_line for "minor lines with poles
> and not towers" was added to the list template, as well as
> http://wiki.openstreetmap.org/w/index.php?title=Template:Map_Features:power&diff=next&oldid=206851
> - In July 2009 rendering minor_line was already discussed on the talk-de mailing
> list.
> - in January 2010 the values minor_line and pole were added to the
> list template,
> after they had proved to be used.
> http://wiki.openstreetmap.org/w/index.php?title=Template:Map_Features:power&diff=401683&oldid=344715
> In June 2011 some user(s) wrote a proposal to change everything above ground to
> 'line' and use other tags with an unlimited list of values for
> describing their differences.
> http://wiki.openstreetmap.org/w/index.php?title=Proposed_features/Power_transmission_refinement&oldid=652518
> After discussions and a wiki vote such a change was even rejected in
> October 2013,
> and the next modified proposal (Power supports refinement) for
> redefining power=tower
> and power=pole was turned down in May 2015. There is no method in osm to have
> the mappers resurvey, reclassify and retag the old data at a whim, nor
> a method to
> propagate the changes in the contested meaning of tags to (even unknown) data
> consumers.
> (Digging up these dates I did see a "(overground)" thrown in the
> 'line' definition to
> clarify, but already lost where it was originally. )
> In summay, the tags have been used for 9 years as such:
> - power=tower: high voltage towers, usually steel latticework
> - power=line: overhead lines on strung on high voltage towers
> - power=pole: smaller supports, usually one-legged and/or wooden
> - power=minor_line: other overhead power lines that don't qualify as power=line
> Do note that even if a 'minor_line' has two bigger towers in the
> middle, for example to
> cross a river or similar, the line as a whole is still minor_line. The
> border case of a
> remote mapper using the wrong tag for a line or minor line wrongly
> identified from aerial
> imagery is no different from remote road classification: the local
> mappers can and will
> correct it later.
> -- 
> alv
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