Clarifying power=pole vs power=tower

General talk Tagging general discussion
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The distinction between power=tower and power=pole is currently quite confusing to mappers. It would be good to clarify this, but I’d like to discuss the best approach.

Currently, the situation is:

  • Carto renders power=tower at the same zoom level as power=line, and power=pole at the same (higher) zoom level as power=minor_line.
  • JOSM raises a validation error if pole is used on a line, or tower is used on a minor_line.
  • According to the wiki:
    • pole is a single (often wooden or concrete) pole
    • tower is a large structure used to carry high-voltage electrical transmission lines […] traditionally constructed from steel latticework, but different designs such as tubular or solid towers are also sometimes seen.

There are a number of cases where the current approach is unclear or insufficient:

Transformers on a double pole

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These are quite common in the UK on 11 kV lines, but the wiki doesn’t mention them. This isn’t a “single pole”, but it’s not really a tower - the rest of the line will be supported on poles. I think this should probably be power=pole, and the wiki should be updated accordingly.

Low-impact wooden supports for major lines

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These are increasingly common in the UK on smaller 132 kV lines (which are definitely power=line). The best approach here is less clear – while they visually look a lot like other power poles, there’s a strong temptation to map these as towers for the renderer (and JOSM’s validator).

Tubular steel supports for major lines

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Common in the US and China, these are a “single pole” but they again often carry major lines (or a combination of major and minor lines). An inexperienced mapper might call these a pole, but they probably should be tagged as a tower.

They’re not currently mentioned on the wiki (and in fact I can’t seem to find a picture of one on Wikimedia Commons - if someone lives near some and can get a photo, that would be good!)

Towers on minor lines

In some situations (particularly in the case of longer spans), larger lattice towers are used intermittently on lower-voltage lines which are clearly power=minor_line. Tagging these as power=tower will result in the JOSM validator complaining, and will also result in Carto rendering the tower at a lower zoom level than the line it’s carrying.

Ultimately I consider the difference between pole and tower (like the difference between line and minor_line) to be primarily of interest to general-purpose renderers, which can use these tags to easily render more significant power lines at a lower zoom level. (Specialist renderers like Open Infrastructure Map can use the voltage to make this distinction.)

The main issue here is that if you use the “wrong” pole/tower tag for the type of line, it will render at a different zoom level and look weird (particularly in the case of a tower on a minor_line). This provides a fairly significant incentive to tag for the renderer.

At the very least, I’d like to get more examples of these shown on the wiki so that it’s clear to mappers what the correct tags are.

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The ‘new’ power tower is the last one, type tubular so is offered in the power tower preset of JOSM. Seen the first appear around 2000, think they’re monsters same as those windturbine masts of 150-200 meters.

The second last I’ve nicknamed rake, well recognisable in aerials, always 3 cables, The top I have no name for. We have some usually of concrete and a cross beam halfway up. With transformer I’ve not seen them. 1/2 I’ve classed as pole absent a technical designation of 2.

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I think the basic problem is that we have adopted, for no good reason a “tower or pole” dichotomy, and that there are two things that are topologically poles, but very different. One is the basic wood thing used in distribution and the other is the very tall bigger, usually metal, thing used in transmission.

I would propose labeling the big ones transmission_pole or big_pole or some other name. And then people can stop saying “it’s a big pole so I’m calling it a tower” – which I find to be nonsensical.

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I guess the current render/josm can be said to say that tower does not mean tower, but a structure that supports transmission, and that pole does not mean pole, but a structure that supports distribution. If that’s how it is, the wiki should say exactly that and not talk about physical form, and explain that the words are historical baggage and should be treated only as codepoints, not according to their ordinary meaning.

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Small lattice towers are quite common in minor lines where I’m mapping, so JOSM should not be complaining about this

Should be fairly easy for a renderer to treat towers and poles as equal, and show them at the same zoom level as the power line they are carrying.

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This makes sense for 2D renderers, but I wonder about existing 3D renderers that make quite a visual distinction between power=tower and power=pole. Maybe these tags’ definitions need to be focused on physical footprint rather than function, since the function can already be inferred from what the tower is connected to.

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StreetGL and I think F4Demo too show towers as lattice towers, gargantuan. Not went to look when tagging tubular. We have many lattice structured here in the range of 15m… they’re often inserted in regular lines when a longer distance has to be scaled, say a valley / river. No matter specifying the height, all still one size fits all, ginormous. As for wood, here very rarely power, 99.9 phone lines. Most all is above ground. Read there’s 6 million poles in France… imagine all were mapped in OSM. Italy wont be far off from that number.

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Hello

One basic criteria I use since a few years now is :

  • One single part stuck in the ground is a pole (whatever it supports a transmission or a distribution line)
  • Several parts assembly in place is a tower

So two or more poles assembly (H-frame for instance) or tubular steel supports composed of several sections are actual towers.

It’s visual and easy to distinguish.

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Those masts, picture 3 in the OP, are not stuck in the ground… they’re on deep seated concrete footings same as wind turbines, screwed on by umpteen heavy bolts.

(and so stumbled today on a not noticed before a wooden pole today that carried both power cable and telephone line separately, so ticked the communication=line box on the preset. Yet in our garden the power pole of metal and wooden telecom pole stand not 1 meter apart)

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Some poles may not be buried in the ground too (especially for wooden ones that rot along years) but hold by a concrete footing. They’re still poles anyway as a single piece of wood.

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From a U.S. and maybe Canadian perspective, here are stereotypical subtransmission poles (power=pole) carrying low-voltage lines (power=minor_line):

These wooden poles are omnipresent. They usually double as telephone poles, so we call them utility poles.

Pylons for power transmission (power=tower) come in a variety of form factors that vary by region and operator. In some regions, wooden ones are not uncommon. Here are some common form factors carrying mostly high-voltage lines (power=line):

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Maybe we need power=pylon as an additional ‘official’ option, the majestic number of 12 uses per TagInfo. + 1 as power=Pylon :upside_down_face:

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Sort of off topic, but what does “subtransmission” mean? In the US, at least in the ISO New England area, there is a great divide between transmission and distribution. While it isn’t actually about voltage, the lowest transmission I see is 69 kV and maybe there’s something like 35 here and there. The highest distribution I see seems to be 13.8 kV.

But perhaps in larger utiliites there are substations that connect to transmission at e.g. 115 kV and then they step down to 30 kV ish and connect that to other substations which then are at 13.8 kV to customers. From the point of view of ISO-NE, these would be distribution because they are on the customer-utility side of the interface. But they are sort of like transmission in that it’s substation to substation.

But that’s speculation. what is the definition of subtransmission in the ulitity world, or is it an OSM term, or ?

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You pretty much guessed the correct answer to your question: “subtransmission” lines are of some intermediate voltage between a higher voltage ‘primary’ transmission line, and the distribution.

E.g. I live a few kilometres from a transmission substation that receives 240 kV on the primary side and outputs 138 kV on the secondary side. The 138 kV lines feed distribution substations that step down to 25 kV, which is distributed out to the neighbourhoods. In this case the 138 kV is “subtransmission” between the 240 kV transmission and 25 kV distribution networks.

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Ack, I was going off the Wikimedia Commons categories, but i probably should’ve written “distribution” to be more precise about what I was referring to. I don’t know where any intermediate subtransmission level would fall on the pole–tower or line–minor_line divide. I’ve probably tagged them inconsistently in the past, but I’m confident that a more experienced power mapper has corrected my tagging since then.

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There are a bunch of the examples at Key:design - OpenStreetMap Wiki. For example,

… would be power=pole, design=h-frame. I don’t think the design=* key sees much widespread use though…

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You’re underestimating by a few million to include 400+K of h-frame per TagInfo.

Just edited the custom preset for (utility) poles to include this feature… not in standard JOSM presets. As noted in a previous post of mine the H frames are not particularly big here, maybe 1.5 height of a regular pole and not seen here with anything on the cross bar. The structure i’ve seen are slightly further apart at the footing compared to the top.

Sometimes seeing two regular wooden poles maybe meter apart at base and fixed together at the top often at points where the line changes direction. Can’t see that as a tower… tagged as pole. No idea what this ‘design’ would be called. There’s a long list including a bipole, The wiki only gives tower designs.

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I guess so, haha. :joy:

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In your 240/138/25, I get it that 138 is in between, but around me the 115 kV is solidly transmission in terms of utility interconnect agreements. In the case you are talking about, is the 138 operated by the utility that is doing distribution, rather than by or on behalf of the regional grid operator? What makes it “sub”, when it seems, apart from who operates it, entirely qualified as transmission?

The problem i have with the tagging scheme is that it’s fuzzy, and we seem to have multiple cases of 2 tags for 3 situations.

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As a matter of fact: yes, the 138 kV line in that particular case is operated by the distribution company! It only serves their distribution substations. :smiley:

But that’s not to say the transmission company doesn’t also operate 138 kV transmission lines elsewhere. Plus lines at voltages as low as 69 kV and as high as 500 kV—both AC and DC—out in the boonies. :laughing:

Anyway, as you wrote above, this was all something of an off-topic question. It doesn’t really matter whether a 138 kV line is “sub-transmission” or “transmission”: it’ll be strung along a structure much taller and more substantial that a simple distribution pole.

Example, from BC Hydro:

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It doesn’t really matter whether a 138 kV line is operated by the transmission company or distribution company.

You were correct in your earlier analysis: in the current tagging scheme it “can be said to say that tower does not mean tower, but a structure that supports transmission, and that pole does not mean pole, but a structure that supports distribution.” It relies on the mapper to know the difference, that something pole-shaped might be a power=tower if it’s supporting a (sub-)transmission line.

I think I understand where Russ was coming from in the first place, but to me the distinction seems pretty clear:

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You might colloquially call the thing holding up the 138 kV a ‘pole’, but the difference is pretty apparent to me…

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