Some of the dams are just tags as waterway=dam (like Mbali Dam), while others (Like Hoover Dam) are tagged as building=yes along with waterway=dam.

Is there a standard procedure for tagging these? I ask because one Mbali Dam appears as cyan colored while Hoover Dam appears as red (due to the building=yes tag) and I can imagine that might be confusing for some editors.

asked 14 Apr '16, 16:11

bddavidson's gravatar image

accept rate: 100%


I also find it humorous that Hoover Dam is tagged as going into service in 1931 and closing in 1936. I'm fairly certain it's still in service. :)

(14 Apr '16, 17:08) alester

@alester: I wonder what that was supposed to mean - according to Wikipedia, construction has started in 1931, and finished in 1936. I don't think that the lifecycle tags have a provision for this; also, IMNSHO the construction dates are not something that's mappable (unless currently in long-term progress).

(15 Apr '16, 08:59) Piskvor

After some deliberation, I have decided to make a minimal edit and only fix the incorrect *_date tags. Hopefully it's tagged better now - I wouldn't want to trigger an edit war, since it's a high-profile structure (pun not intended), so I didn't touch the building tag.

(15 Apr '16, 12:54) Piskvor

In general, dams are not buildings, though I'm sure there are a few exceptions. Hoover Dam has been tagged as a building since it was added to the map, likely to make it show on the map because waterway=dam wasn't rendered on the standard rendering until a year ago. There's really no way you could validly consider Hoover Dam to be a building, because it's a solid block of concrete with only the occasional interior service space.

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answered 14 Apr '16, 16:56

alester's gravatar image

accept rate: 28%

Consider every structure that can be entered through an entrance with doors and windows to be a building. A dam man_made=dam could be build out of dirt, stone, sand, concrete or steel. The OSM rules should be considered to be part of a change. Its a ships rule, the beacons are changed if the tide changes. OSM should enter into today.

(14 Apr '16, 17:23) Hendrikklaas

Unfortunately it isn't that simple. For example, here's a building with no windows (it's a proposed legal marijuana growing operation; sorry for the Google).

The material out of which a dam is constructed is irrelevant when determining whether it's a building or not. It only matters whether it has any significant interior space, which dams generally do not.

(14 Apr '16, 17:48) alester

A lot of man made structures have facilities for people to walk in and through at least for service purposes: bridges, communication towers, sewers and yes, dams. Larger dams usually have a service tunnel where inspections are made and measuring instruments for leakage and settling are installed. Additionally, there might be machine rooms for water inlets our outlets, power generators etc.

The question is what do we want to convey with the message "this is a building"? For the usual detached house, apartment building, barn, church etc this is clear. For the rest I regret there is no clear line we can draw. There's one big motorway bridge here in the city which has large service corridors. I would still do with highway=* and bridge=yes. Then there is another bridge which houses some bigger rooms that have been converted to artists' workshops. That might warrant to give this bridge its own building tag.

For the dam I would see it similarly. Is it only a service tunnel that gets inspected once a day, just leave it with dam. But are there also additional facilities like machine rooms in there make it a building (or map both separately if possible).

I guess as so often the answer is "it depends on your gut feeling". <shrug>

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answered 15 Apr '16, 12:02

TZorn's gravatar image

accept rate: 14%

edited 15 Apr '16, 12:36


Hmh. If I were mapping from scratch, I would surely tag the powerhouse and both the Nevada and Arizona wings as "building"; for the dam structure itself, I don't think it's necessary.

Now - is the building tag on this dam incorrect enough for removal? I'm not sure, so I would choose the usual way and leave it alone.

(15 Apr '16, 12:37) Piskvor
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question asked: 14 Apr '16, 16:11

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last updated: 15 Apr '16, 12:55

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