Key:indication:*

Prefix indication:*
Description
Prefixes any OpenStreetMap tag designated by remote signage
Group: properties
Used on these elements
See also
marker=*
Status: approved
taginfo: indication:*

This page describes a key prefix rather than a simple key.

The indication namespace prefixes any OpenStreetMap tag on a given feature to state it designates any information about something else nearby.
It was first of all designed and reviewed to be used in combination with marker=*, particularly on utility markers to hold the information about something invisible, mostly buried near of any marker like a power cable or a pipeline.

Usage of this namespace may generate a vast diversity of prefixed keys, like indication:man_made=* or indication:power=* depending on what is designated.
This namespace is supposed to be used with existing and documented OpenStreetMap tags.
It shouldn't be necessary to create actual wiki pages for these keys as the documentation of the prefixed tag applies to avoid duplicates.

How to use

On any marker seen on ground, use this prefix with tags that best described what read on it about designated feature (see examples below).
Use this namespace only about remote properties. The marker's own property, like its colour or material won't be prefixed as they are not indication but actual information about the marker itself.

How to extend

As any namespace, it's technically possible to use it with additional keys that the one it has been reviewed for.
Several other use cases has been mentioned in the original proposal. They weren't reviewed so far and would need further investigation if necessary in the future.

First of all, discuss any new significant usage you want to promote. It could possibly require a formal proposal and a vote according to the dedicated process.
Secondly, as prefixed keys won't get a dedicated page, don't forget to add supplementary examples below to keep track of it.

Underground utilities

Photo	Location	Tagging	Note
	France	marker=pedestal indication:man_made=pipeline utility=gas operator=GRTgaz colour=yellow	Such markers are obvious in France and mark buried high pressure gas pipelines. indication:man_made=pipeline is appropriate to clearly indicate the marker marks a pipeline.
	UK	marker=post indication:power=cable utility=power operator=National Grid colour=yellow	As Power cable is written on the marker, we use indication:power=cable here.
	Croatia	marker=pedestal indication:power=cable utility=power colour=white indication:voltage=110000	As Energetski kabel is written on the marker, which translate to power cable so we use indication:power=cable here and additional indication:voltage=110000 to keep track of 110 kV information without energizing the marker itself.
	France	marker=plate indication:emergency=fire_hydrant utility=water operator=Eau de Paris colour=white ref=751120563 position:distance=6.40 indication:diameter=150	This is a typical hydrant marker in Paris. It gives several properties of designated hydrant. The hydrant is fed from water main and gives its diameter, so utility=water + indication:diameter=150 applies. The marker is placed at a given distance from the hydrant. Regarding the reference, ref=* is fine but some may argue it's the hydrant's ref, not the marker's ref so indication:ref=751120563 could also be valid, depending on local practices and views. Maintaining utility=hydrant would prevent from using more appropriate utility=water here.