[Tagging] mast / tower / communication_tower (again)

EthnicFood IsGreat ethnicfoodisgreat at gmail.com
Fri Oct 26 15:29:41 UTC 2018


> Date: Thu, 25 Oct 2018 19:57:38 -0400
> From: Greg Troxel <gdt at lexort.com>
> To: Graeme Fitzpatrick <graemefitz1 at gmail.com>
> Cc: OSM Tag <tagging at openstreetmap.org>
> Subject: Re: [Tagging] mast / tower / communication_tower (again)
>
>
> Graeme Fitzpatrick <graemefitz1 at gmail.com> writes:
>
>> A mast is a tall, slim structure supported by guys, usually with external
>> access only
> This reliance on guys does not align with engineering reality.  guys are
> needed depending on forces/loading, and there can be unguyed masts, that
> are exactly like guyed masts but a bit shorter.
>
>> A tower is a tall, slim free-standing structure, usually with internal
>> access. (Possible include from wiki: "Towers are specifically distinguished
>> from "buildings <https://en.wikipedia.org/wiki/Building>" in that they are
>> not built to be habitable but to serve other functions.")
> again towers can need guys if they are really tall (300m), even if they
> are the same construction that would not need guys if only somewhat tall
> (30m).   Guy wires do not make a tower not a tower, in the language of
> antenna support structure.
>
> Perhaps this is a UK vs US English thing, or a lay vs radio engineering
> thing.  But your definitions (to a US engineering type) seem seriously
> wrong.
>
> Now, if you're coming at this from "tower is building that's mostly used
> to get something high, and not for inhabitation" and "mast is an
> antenna support structure that is not a building.  Note that things that
> engineers call towers, such as structures made out of lattice like Rohn
> 65, are called masts in OSM because they are not buildings"  then I can
> see that.  But in that case, there is no requirement for a mast to be
> guyed.  I can certainly see a "guyed means not tower" in that world,
> because buildings don't have guy wires.
>
> For an example of something used in communications (an American thing,
> but totally normal and other countries surely have equivalent things
> with the same characteristics):
>
>    http://www.rohnnet.com/rohn-65g-tower
>
> which says right there can be up to 500 feet when guyed and 80 feet not
> guyed.  But it's the same thing in both cases -- it just needs more
> support when taller where the forces get bigger.
>
> Around me, antenna support structures for cellular (mobile phones) are
> typically 30' and I have never seen one guyed.  Some are tube-like
> (because planning boards require that) and some are lattice.  But they
> are not buildings -- they are antenna support structures that *maybe*
> one person could climb inside of, but maybe not.  There are also antenna
> support structures for TV, which are typically lattice and 300m tall,
> and always guyed.  Everyone calls these towers.   To call the 30m ones
> towers because they are not guyed and the 300m ones masts because they
> are guyed makes zero sense in US English usage, either for the general
> public or for engineers.
>
> As I said earlier, things that are maybe 10cm in diameter are usually
> called masts.  These are very minor and not really used in
> telecom/broadcasting.
>
> So maybe we just need
>
>    man_made=antenna_support_structure
>
> for all things which are not buildings and basically exist to support
> antennas, and avoid the tower/mast word choice, which is pretty clearly
> contentious and/or confusing.
>
>> Do we need to worry about height for rendering purposes? (which is what
>> this original discussion started from!) If so, would a simple break-down
>> into height >30 (m), 30-150, 150+ work?
> I don't know why you are proposing classes of height. It seems like
> speed limits and road width that we should have a height tag and people
> should make their best estimate, and renderers can do what they think
> sensible.  Adding some sort of bins for heights in the tagging scheme
> seems like unnecessary complexity that brings no value.
>
>

+1 to all your points.

Mark



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