[Tagging] mast / tower / communication_tower (again)

Greg Troxel gdt at lexort.com
Thu Oct 25 23:57:38 UTC 2018


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.




More information about the Tagging mailing list