[Tagging] mast / tower / communication_tower (again)
gdt at lexort.com
Tue Oct 9 14:05:30 UTC 2018
Graeme Fitzpatrick <graemefitz1 at gmail.com> writes:
> On Tue, 9 Oct 2018 at 03:58, SelfishSeahorse <selfishseahorse at gmail.com>
>> There is a risk that towers and masts are defined differently in
>> English, but perhaps Martin's idea to combine the two definitions
>> would make sense nevertheless.
Part of the issue is UK English vs US English, and usage common in
professional or amateur radio language vs public usage.
The same thing will be:
UK: Mobile phone mast
US: cell tower
> So, how about we clean up the various mixtures of definitions, &
> conflicting photos, to:
> man_made=mast: a vertical structure, supported by external guys and
> anchors. (Possibly also include: Has no internal access, can only be
> climbed by ladder?)
> man_made=tower: a tall, slim, freestanding vertical structure with internal
The guy wires or not is made into the main thing here, but it's really a
detail. In amateur radio, the same kind of tower (e.g. Rohn 45
sections, which are lattice) can sometimes be freestanding and sometimes
guyed. Adding guy wires does not make them a mast. There is a TV
antenna structure near me that might be 300m tall, is lattice, and it
has guys. It is definitely "tower" by US usage.
In US amateur usage, mast often refers to something that is up to maybe
4" in diameter (and thus basically not climbable). Often guyed, but not
always. Basically, you add guy wires when you need to, which is a
function of material strength, height, wind loading of antennas on top,
and the wind levels you want the thing to survive.
In US cellular infrastructure, there are big lattice things that look
like someone obviously could climb them. There are also things that are
several feet in diameter and round. For all I know, these are the same
towers inside with a fairing to make them look better, and some may be
climbable internally. But they are big, and function the same way, so
I would call them tower.
> man_made=communications_tower: to be deprecated (but also create a new
> tower:type=multipurpose for the massive 150m+ combined communication /
> observation / tourist attraction buildings)
> man-made=pole: (currently not defined) a usually vertical column used as a
> support for overhead utilities such as cables or antennae (Do we need a
> height reference eg a pole is <15m - if it's 15m+, it becomes a tower?)
So what's the difference between a pole and a mast?
A pole is used for power, and is usually wood, and a mast for antennas,
The world has a variety of shades of these things and there are going to
be edge cases. The question is what we are trying to represent and why.
Arguably having a height tag is the most important thing for renderers.
So I would say of tall thin things to hold other things up high (which
leaves out arguing about vertical antennas):
tower: anything lattice, anything > 1m diameter, anything > 50m high.
ok to be guyed or not. (so a 4m triangular lattice with 0.3m edges is
still a tower, but that's ok with me)
pole: anything not a tower, probably cannot be guyed, and either wood
or > 0.25m diameter, such as is typically used for power lines (wood
in distribution, and big wood or steel tubular in transmission (which
also uses lattice).
mast: anyhing not a tower or a pole. ok to be guyed or not.
Typically <= 0.1m diamater, but anything up to 0.25m is ok.
This definition proposal admits that these are all subtypes of the same
thing, and that things that people call towers are more substantial than
things called masts.
Really what I suggest is not so far from what you suggested, except that
I am de-emphasizing guying and calling anything that is big/substantial
by any of several metrics a tower.
I would probably also call broadcast antennas around 1 MHz "tower", even
though there the point is not to hold up something but the structure is
the antenna. We could do the same for something used as an antenna that
is otherwise a mast. Map users after all usually want to use these as
navigation references - at least that's why there are shown on
traditional nautical charts.
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