Graeme Fitzpatrick <graemefi...@gmail.com> writes: > On Tue, 9 Oct 2018 at 03:58, SelfishSeahorse <selfishseaho...@gmail.com> > wrote: > >> 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 > access 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, usually metal? 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. _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
