Graeme Fitzpatrick <graemefi...@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. _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging
