Proposal:Tagging scheme for windmills and watermills

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Tagging scheme for windmills and watermills
Proposal status: Voting (under way)  Icon arrow down (89599) from The Noun Project
Proposed by: AntMadeira
Applies to: Applies to node area relation
Definition: Differentiates building=windmill from man_made=windmill and creates the new key windmill=* to refine the use of both elements.
Rendered as: picture
Draft started: 2025-01-27
RFC start: 2025-02-16
Vote start: 2025-06-28 00:00:00 (UTC)
Vote end: 2025-07-19 23:59:59 (UTC)


Proposal

This proposal arises from the ambiguity between the tags building=windmill and man_made=windmill, whose wikis are almost indiscernible. The aim is to remove the association of the tag man_made=windmill to the building scheme, leaving building=windmill for those structures built as buildings to operate with the help of the wind (mostly to mill grains), and man_made=windmill to the devices which can operate independently or inside a building, thus clarifying the differences in their respective wikis. The same applies to building=watermill vs. man_made=watermill.

Rationale

As it happens today in OpenStreetMap, a windmill (normally mapped with the tag man_made=windmill) must be tagged with building=yes (or building=windmill or even building=industrial) to be correctly rendered in the map. Thus, it doesn’t make sense to have two tags to map a building when you can have only one, which fits perfectly into the building=* scheme.

After consulting the community in the forum, there were some ideas to try and solve this ambiguity and contribute to more logical and specific tags, which fits in the already existing schemes of building and man_made.

The main idea is to map windmills and watermills as buildings when the structures were clearly constructed with that purpose, and leave devices or apparatus included in the man_made=* tag. These devices can exist independently from buildings (see examples below) or mapped as the device inside the building (if it still exists). To specify the use of the windmill, this can be further refined with the the new proposed keys windmill:function=* and watermill:function=*.

As discussed in the forum, due to the fact that the word "windmill" is used in many places around the world as synonymous of various structures/buildings/devices, and in order to take advantaged of the more structured and refined definition of man_made=windmill, it is also proposed to deprecate man_made=windpump in favor of man_made=windmill + windmill:function=water_pump.

Wind turbines for energy production (also called "windmills" in some places) have their own well established scheme and will not be included in this proposal.

Tagging

The following tables includes tags/keys which will be altered, created or deprecated.

Useful combinations are also presented.

Altered

tag description examples actual use
building=windmill This tag would be used only for buildings purposely built as windmills, i.e., to harness the power of wind by means of blades or sails to mill grains (mostly), drain water, saw wood or other purposes. The windmill:structure=*, windmill:function=* and windmill:vanes=* keys can be added to better describe the structure and use of the building.

The tag man_made=windmill should be maintained if the device still exist inside (see examples below). Preferably, man_made=windmill should be a node node if the building is mapped as an area area.

More details at taginfo
man_made=windmill This tag should no longer make reference nor used to define buildings, since there's a more structured and appropriate tag for that. Instead, it should be used for devices with various purposes operated with wind energy. These can be external or internal devices. The present proposal suggests the transition of man_made=windpump tag to this one, deprecating the latter. The windmill:structure=*, windmill:function=* and windmill:vanes=* keys can be added to better describe the structure and use of the device.

Pros:

  1. no longer use man_made=* to define buildings;
  2. the possibility to render windmills has buildings on the map, with their respective icon;
  3. reserve the more well known term "windmill" for those windmills which are not buildings and serve to pump water (currently man_made=windpump);
  4. introduce the key windmill:function=*, which can be expanded to refine the use of the device (pump water, cut wood, mill grain, etc.).

Cons:

  1. For those windmill buildings already mapped using this tag, the tag building=windmill should be gradually added. For buildings in ruins, abandoned or disused, where the device is no longer present, this tag should be removed;
  2. The need to accommodate the migration of man_made=windpump to man_made=windmill (see below).
More details at taginfo
man_made=windpump Since this element is considered a windmill, mainly in the USA and Australia, where they're more frequently used, this tag should be deprecated and migrated to man_made=windmill. It then can be further refined adding windmill:function=water_pump + windmill:structure=lattice_tower. A Maproulette challenge can be use to help in this task.
More details at taginfo
man_made=watermill This tag should no longer make reference nor used to define buildings, since there's a more structured and appropriate tag for that. Instead, it should be used for devices with various purposes operated with water energy, be it inside or outside buildings. The proposed watermill:function=* tag can be added to define its use.

Like with man_made=windmill, this tag should not be removed if the device still exists.

More details at taginfo
windmill:type=* This key already exists and it's used to indicate the architectural/structural style, not the use. In the discussion page, it was proposed that due to its low usage, it could be adapted to a more descriptive key, one that can be better distinguished from windmill:function=*. The proposed key is windmill:structure=*. The existing wiki should be adapted to be used with building=windmill (because it is a structural description) and can have the following values (more can be added): post, tower, smock, tjasker, lattice_tower, roundhouse, etc.
More details at taginfo
windmill:vanes=* This key already exists and it's used to indicate whether a windmill still has vanes (building or device). Its wiki should only be adapted and expanded to be used both with man_made=windmill and building=windmill and can have yes, no as values.
More details at taginfo

Created

tag description examples actual use
building=watermill This tag would be used only for buildings purposely built as watermills, i.e., to harness the power of water by means of wheels or other rotative devices to mill grains, fruits or to cut logs. To define its use, the proposed watermill:function=*and watermill:method=* keys can be added.
More details at taginfo
windmill:structure=* As mentioned above, this key would be a migration from windmill:type=*, due to the ambiguity of the word "type", which could mean "type of building" or "type of use".
windmill:function=* This tag is used to indicate the type of the windmill regarding its use, whether a building or a device. Possible values are windmill:function=water_pump, windmill:function=sawmill, windmill:function=grinder, etc.

For the grinder value, the product can be further specified:

More details at taginfo
watermill:function=* Like with windmills, a watermill can be used to several purposes. Possible values are watermill:function=sawmill, watermill:function=water_pump, watermill:function=grinder, watermill:function=energy, etc.

For the grinder value, the product can be further specified:

More details at taginfo
watermill:method=* Based on Watermill#Operation, there are various methods used in a watermill.

This key would be used to distinguish between them.

man_made=water_wheel This tag can be used to map water wheels outside watermills or in cases where the device is the only feature remaining.

Based on Watermill#Operation, there are different kinds of water wheels.

More details at taginfo

Deprecated

Additional tags

  • material=* - the most common construction material of the building
  • name=* - some historic buildings have their own name
  • start_date=* - the date when the element was created
  • craft=grinding_mill - typically mapped with a node node, indicates if the windmill is in operation, with people regularly using it to grind cereals
  • craft=sawmill - typically mapped with a node node, indicates if the windmill is in operation, with people regularly using it to cut wood into timber
  • ruins=yes - indicates if the building is in ruins
  • tourism=museum - indicates if the building originally built to be a windmill/watermill is presently a museum
  • tourism=guest_house - indicates if the building originally built to be a windmill is presently a guest house/chalet/etc.

Examples

type example image tagging usage description
Buildings way 856992438 node or area A building built as a smock mill to grind grains. It still has vanes.

The already existing tag man_made=windmill would be maintained, because the device still exists inside.

node or area An old and ruined windmill without its vanes. There's no man_made=windmill any more, because the device no longer exists.
node or area An operating wooden windmill which is used to pump water.
node 298919173 node or area A windmill building operating as sawmill, with reference to its type, to the existing vanes and the craft. The device man_made=windmill still exists inside.
node or area An old windmill refurbished as a guest house. There's no man_made=windmill tag, because the device no longer exists.
node or area A building built as a watermill operated by the running water of a stream.
Devices node A windmill which is not a building, also known as windpump.
node A wind operated mill.
node A tjasker, a windmill device used to pump water.
node A water operated mill device used to mill grain.
node The water wheel of a watermill can also be mapped separately.

Rendering

The current icon for a windmill building would need to be attributed to building=windmill and not to man_made=windmill.

The icon for a watermill building could be something like this (used by HOT style):

Pages affected

External discussions

The original discussion about this subject can be found at the community forum:

Comments

Please comment on the discussion page.

Community forum: https://community.openstreetmap.org/t/rfc-feature-proposal-tagging-scheme-for-windmills-and-watermills/125959

Tagging mailing list: https://lists.openstreetmap.org/pipermail/tagging/2025-February/068098.html

Voting

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  • I oppose this proposal I oppose this proposal.

The problem that the proposal tries to solve is real, but there is something basically wrong: man_made=windmill is used 12000 times, building=windmill 800 times, but the proposal is to eliminate man_made=watermill.

For watermills: building=watermill 400 uses, man_made=watermill 14000 uses.

Then the proposal does not address the differentiation between active/disused/dismantled.

There are also the "historic" tags: historic=watermill 1000 uses, historic=windmill 300 uses.

--voschix (talk) 09:41, 28 June 2025 (UTC)

Hello, @Voschix:. Thank you for your vote. Where does the proposal state that man_made=watermill should be eliminated? Please, read the proposal carefully. This was something debated in all channels of the OSM community through several months. The historic scheme is not mentioned because this proposal doesn't change anything in it. Besides, historic shouldn't be synonymous of "old". About the differentiation between active/disused/dismantled, it was never brought out during all these months of discussions, mainly because this proposal doesn't change any of that. You can still define the state of a building without that being written in the proposal. Still, you have an example of a ruined windmill in the examples' table.--AntMadeira (talk) 13:23, 29 June 2025 (UTC)
  • I oppose this proposal I oppose this proposal. This proposal seems to suggest tagging all windpumps as windmills, which seems very, very silly? Even if I have misunderstood that part (and I hope I have) it is clearly far too confusing to be accepted as is. Also, any tagging proposal that suggests a "rendering" section also makes no sense. SomeoneElse (talk) 12:32, 29 June 2025 (UTC)
I answered this comment here. --AntMadeira (talk) 13:23, 29 June 2025 (UTC)
Actually no, your reply wasn't there it was here, but more importantly it did not address the issues. SomeoneElse (talk) 13:43, 29 June 2025 (UTC)
  • I approve this proposal I approve this proposal. --Topolusitania (talk) 20:29, 29 June 2025 (UTC)
  • I oppose this proposal I oppose this proposal. I'd probably view this proposal more favourably if it was only about windmills; however it also concerns itself with watermills and I don't agree with the classification. The proposal correctly recognises that the `man_made=watermill` is basically the power generator. The structure of the building and its purpose should then be in `building` and `amenity` respectively - using `building=watermill` as if the generator requires a particular building type doesn't make sense. Similarly, windmills tend to look the same, but that's only partially because of the generator. And then there is https://de.wikipedia.org/wiki/H%C3%BCvener_M%C3%BChle which combines watermill and windmill.

In short, tagging `building=yes` together with `man_made=windmill` doesn't seem like an issue to me. It's a building that happens to contain a mechanism to utilise the wind. --Jofban (talk) 21:29, 29 June 2025 (UTC)

  • I oppose this proposal I oppose this proposal. Reasons are the same as written by SomeoneElse. ---- Something B (talk) 08:26, 1 July 2025 (UTC)
@Something B: Answers to SomeoneElse's reasons:
  1. The reason to propose the deprecation of man_made=windpump in favour of man:made=windmill + windmill:function=waterpump has elaborately been discussed in the original topic Deprecate man_made=windmill (as from around #60) because in large parts of the world where these windpumps are common (US, Oz, Spain) the common name for them is simply “windmill” and nothing else.
  2. Rendering is just a side effect and has nothing to do with the proposal for a structured tagging of wind- and watermills.
  3. The historic scheme is well defined and this proposal doesn’t change or affects any of it. You can add whatever you want to the historic tag, and besides, there are many mappers in the OSM community against the use of the historic scheme to denote “old things”. Historic should be something verifiable, where something important happened, not to use arbitrarily to tag old or antique things. --AntMadeira (talk) 14:41, 5 July 2025 (UTC)
  • I abstain from voting but have comments I have comments but abstain from voting on this proposal, I encourage to continue discussion on this useful proposal. Good changes have been proposed and too few links to pumps, with man_made=pump or pump_mechanism=* instead of windmill:function=water_pump or with wind turbines as well, pretty much contemporary instance of wind mills, prevent me to vote yes. Fanfouer (talk) 20:59, 1 July 2025 (UTC)
  • I approve this proposal I approve this proposal. I like the structured approach. Good job! --Map HeRo (talk) 13:08, 2 July 2025 (UTC)
  • I oppose this proposal I oppose this proposal. I think deprecating the windpump tag for no benefit is already a show stopper. The rest looks ok at first glance but I didn't bother to look deeper into it for now, i.e. only buildings should get a building tag (as it is proposed here), and of course we should not tag or map incorrectly for the renderer, and we cannot influence rendering with proposals, this would be out of scope. --Dieterdreist (talk) 16:17, 3 July 2025 (UTC)
@Dieterdreist: The reason to propose the deprecation of man_made=windpump in favour of man:made=windmill + windmill:function=waterpump has elaborately been discussed in the original topic Deprecate man_made=windmill (as from around #60) because in large parts of the world where these windpumps are common (US, Oz, Spain) the common name for them is simply “windmill” and nothing else. --AntMadeira (talk) 14:41, 5 July 2025 (UTC)
  • I oppose this proposal I oppose this proposal. I oppose it primarily because it will result in Windpumps being tagged as Windmills. I find that illogical. Pumping is not Milling. There is a language reason why the word Windmill contains the word mill. I agree there is need to improve the tagging this prosal enagages with, and I apologise for not being part of the discussion before voting no --JassKurn (talk) 17:28, 3 July 2025 (UTC)
@JassKurn: This was discussed in the community's forum, referenced here in the proposal (see answers above). Although a windpump doesn't mill, they are called windmills, not windpumps, in many parts of the world, including USA and Australia. The proposal only tries to accommodate that within the man_made=* tag and use another subcategory to specify its use.
@AntMadeira: We must not tag based on a word used in some parts of world, unless the the object is a specfic entity of a country & language. OpenStreetMap is global so why would you specifically chose a term use by Americans and Australians? --JassKurn (talk) 17:36, 6 July 2025 (UTC)
  • I approve this proposal I approve this proposal. --PedroMTG13 (talk) 20:54, 3 July 2025 (UTC)
  • I approve this proposal I approve this proposal. --Dmfr (talk) 16:31, 4 July 2025 (UTC)
  • I oppose this proposal I oppose this proposal. While this proposal clarifies the case of mills as buildings, it does not address mills as a theme. What about those currently categorised as Key:industrial ? --Severin (talk) 08:09, 5 July 2025 (UTC)
Thank you for your vote, @Severin.menard: . I did not understand what you mean by "theme". This proposal is related to traditional mills, not industrial ones, where wind and water are not part of the milling process. I believe Key:industrial is more suited for industrial mills, not wind or water mills. --AntMadeira (talk) 14:41, 5 July 2025 (UTC)
  • I approve this proposal I approve this proposal. --Caboulot (talk) 15:55, 6 July 2025 (UTC)
  • I oppose this proposal I oppose this proposal. I disagree with the deprecation of man_made=windpump in favour of mis-tagging them as windmills if these are all to be lumped together it should be under a "wind turbine" tag as that's the bit you can actually see converting the wind into rotational motion. --InsertUser (talk) 17:59, 6 July 2025 (UTC)
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