Proposal:Markers subject refinement

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Marker translating to High pressure gas pipeline underground
Markers subject refinement
Proposal status: Proposed (under way)
Proposed by: fanfouer
Tagging: subject=*
Applies to: node
Definition: Addition to existing markers tagging with ability to describe what a given marker is referring to (pipelines, valves, hydrant...)

Draft started: 2023-02-22
RFC start: 2023-04-17

Following Utility markers proposal, it was reported that it's barely possible to clearly indicate what a given marker is referring to.
It's about distinguishing underground features like pipelines or valves and some distant features like hydrants or even road as well.

This proposal is intended to introduce additional solution to solve this issue and provide a better solution to map markers' subject.
It doesn't change what was previously introduced and only intend to provide an answer to this particular problem.


It is proposed the following changes :

As a side effect, pipeline=marker which is currently replaced by marker=* only will be updated to be replaced by marker=* + subject=pipeline.

This proposal won't challenge pipeline=marker status and it will remain deprecated, as reviewed in marker=* proposal. The vote won't be held about pipeline=marker.
The point is to complete the initial replacement that was reviewed previously.


Markers are visual features that indicate the presence of mostly hidden other features. They're not connected to the feature they mark and are mapped as separates nodes in OSM.
Thus, it is necessary to provide a tag to state to which kind of feature they are referring to.

Such information is often written on them to clearly warn of possible danger to anyone passing by them.
subject=pipeline is intended to describe in OSM labels like High pressure gas pipeline underground seen on ground.

subject=* is already used for different purposes and previous discussions shown that it wasn't desirable to extend its usage.
It encourages to introduce a subset of marker=* with subject=*.

pipeline=marker was deprecated by utility markers proposal by the end of 2019 to free pipeline=* from unconnected features. 10k features were moved and 25k remain today.
A complementary solution is now proposed to state a given marker points toward a pipeline and it would improve the removal or remaining items.

Involve markers in relations

An alternative to proposed tagging would be to involve markers in relations with the feature they mark. A similar practice to addresses and associated street relation.

It would be really complex and hard to maintain. It is chosen to give a try to simpler tagging and lesser usage of relations.

Utilities and substances

Proposed subject=* values aren't supposed to mention utilities nor substances.
Proposing gas_pipeline or power_cable for subject=* would break versatility and consistency.

Existing utility=* is already used in combination with marker=* for that and pipeline, cable are better values.

substance=* is actually a property of the pipeline itself. There is no gas or ethylene in markers, but this information could be kept on the marker in description=* if necessary.

Consistency with boundaries

For consistency sake, it would be legit to cover boundaries in this proposal.

Replacement of boundary=marker by subject=boundary was studied and appear to be too big to be done now.
By the way, boundary=* is intended to precise a kind of boundary, not peripheral objects that mark them, just like pipeline=marker that had been deprecated previously.

Consistency with highways

highway=milestone could also be covered by this proposal. It would free highway=* from milestones or distance markers.

Several issues still rise about how to document road's ref referred by a given marker and subject:ref=* could be a suitable option.

Replacement of highway=milestone by subject=road was studied and appear to be too big to be done now.
By the way, highway=* is intended to precise the importance of a road, not peripheral objects that mark them, just like pipeline=marker that had been deprecated previously.


Current marker=* tagging practices don't change.

List of possible subject=* values.
Key Value Comment
subject pipeline A pipeline, often underground, is marked by the marker.
cable A cable, often underground, is marked by the marker.
valve The marker indicates a valve is found next to it, possibly in a chamber or directly accessible
hydrant An hydrant, underground or not, is located next to the marker

Edition management

Affected pages

Tagging to be replaced

Obsolete tag Usage Used for? New tag(s) to use
utility=hydrant 397 on 2023-03-03 A marker referring to a hydrant (underground or not) utility=water + subject=hydrant

External discussions


Underground features

Photo Location Tagging Note
Borne Indication Canalisation Gaz Route Loëze St Cyr Menthon 5.jpg France


Such markers are obvious in France and mark buried high pressure gas pipelines. subject=pipeline is appropriate to clearly indicate the marker marks a pipeline.
Submarine power cable marker, Lepe - - 284348.jpg UK

operator=National Grid

As Power cable is written on the marker, we use subject=cable here.
French Paris hydrant marker.jpeg France

operator=Eau de Paris

This is a typical hydrant marker in Paris.


Voting hasn't started yet.