Proposed features/Key:light source

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Key:light_source
Status: Proposed (under way)
Proposed by: MHohmann
Tagging: light_source=*
Applies to: node
Definition: Location of a light source.
Rendered as: Different symbols.
Drafted on: 2014-03-11

This proposal is a follow-up and restructured improvement of the previous lamp proposal. It completely replaces this old proposal and introduces a new tagging scheme instead.

Description

A light source, which may be a lantern, a street light, a floodlight, a signal lamp or any other device whose primary purpose is the generation of light.

Motivation

Light sources are easily visible landmarks and therefore very helpful to find one's way at night. Besides that, the location and type of light sources helps to judge how good the lighting of a lit highway is, so one can easily avoid dark spots or poorly lit highways on a nightly walk. Further, this information is of statistical significance and answers questions like: "How many and which types of light sources are in a certain residential / industrial area? What is their average distance? What is the estimated light pollution caused by these light sources?" Finally, light sources are an important class of objects in the fields of "micro-mapping" and of particular interest in the 3D visualization community.

One may argue that light sources are artificial, man made objects and should thus be tagged with an appropriate man_made=* tag. However, since there are very different types of light sources which have nothing in common besides the fact that they emit light, there is no reason to use a common tag for these objects. Hence, this proposal instead introduces a new primary key light_source=* with different values for different types of objects.

This proposal allows distinguishing different types of light sources, such as lanterns, street lights, floodlights, signal lamps marking the position of something etc. It does not apply to traffic lights, railway signals etc. which are part of some traffic infrastructure, or displays / screens for information or advertisement purposes.

Additional tagging may allow differentiation between different light generation methods / technologies (electric, gas), colours, electrical power, direction of light emission etc. The need for this can also be seen in the tagging scheme for gas lamps in Düsseldorf, which should be generalized and unified to a global tagging scheme.

Tools

Online map

OpenLayers map showing light sources.

JOSM preset

JOSM preset for tagging light sources.

JOSM style

JOSM style with light source icons.

Taginfo


Tagging

Primary tag

  • light_source=* - Marks this object as a light source. Typical values could be:
    • light_source=lantern - A lantern is a light source whose purpose is to illuminate broad areas. Typical examples are street lights, but the term lantern is more generic and also applies to light sources which illuminate other areas than highways.
    • light_source=floodlight - A floodlight is a broad-beamed, high intensity artificial light typically used at sports events or music stages.
    • light_source=aviation - Used in aviation for, e.g., runway lighting.
    • light_source=warning - Marks the position of hazardous spots, such as wind energy towers, high builings etc.
    • light_source=signal_lamp - A signal lamp is used to convey information / communicate by encoded light signals, e.g., morse code. Not to be confused with a traffic signal, railway signal etc.!
    • light_source= - Other values can be defined if needed.

Optional secondary tags

The following tags may be used to supply additional information on the light source, if desired.

Light generation method

Geometry of the light emission

  • light:aperture=* - What is the angular aperture of a directed light source, i.e., the angular diameter of the light cone emitted from this light source?

Direction of the light emission

  • light:tilt=* - What is the tilt angle for the light cone of a directed light source? Any value between -90 and 90 is allowed.
  • light:direction=N/S/E/W/… - In which direction does a directed light source emit most of its light? Values from Key:direction#Angles and cardinal directions should be used.
    • light:direction=to_street - The new value to_street may be used if there is a uniquely determined point along a street to which the light source points. Use this only if the street and light direction are uniquely determined by the geometry. This applies mainly to street lights.
    • light:direction=to_crossing - The new value to_crossing may be used if there is a uniquely crossing to which the light source points. Use this only if the crossing (and thus the light direction) is uniquely determined by the geometry. This applies mainly to street lights.

Operating times

  • light:lit=* - When is this light source lit (in analogy to lit=* for highways)?
    • light:lit=motion - The light source is switched on by a motion sensor.
    • light:lit=demand - The light source is switched on by demand (for example, by phone call to the operator).
    • light:lit=sunset-sunrise - The light source is switched on and off exactly at sunset and sunrise.
    • light:lit=dusk-dawn - The light source is lit from dusk to dawn. Note that in contrast to sunset and sunrise these are "fuzzy" times, since light sources are usually not switched on and off exactly at sunset / sunrise, but at some (not necessarily exact) time during dusk / dawn.
    • light:lit=20:00-08:00 - The lamp is lit every day from 20:00 to 08:00.
    • light:lit=Mo-Fr dusk-00:00,04:00-dawn; Sa-Su dusk-dawn - The light source is lit from dusk to dawn, but on workdays it is switched off between midnight and 04:00.
    • light:lit= - Other values similar to opening_hours=*.

Miscellaneous properties

  • light:flash=* - Is this light source flashing? (Applies mostly to light sources that convey information instead of just providing light.)
    • light:flash=no - No, the light source emits its light constantly. (Default value.)
    • light:flash=yes - Yes, the light source is (somehow) flashing. If known, use a more specific value as shown below.
    • light:flash=pattern - This light source flashes in a repeating pattern.
    • light:flash=random - This light source flashes randomly.
    • light:flash=2 - One number indicates that this light source flashes regularly. The number indicates the period in seconds, i.e., in the example within 2 seconds the light source is switched once on and once off.
    • light:flash=0.5,2,0.5,1 - An even count of numbers, separated by comma (,), describes the flashing pattern. The first number indicates for how many seconds the light source is switched on, the second indicates how many seconds it is switched off, and so on. In the example it is 0.5s on, 2s off, 0.5s on, 1s off, and then the pattern repeats.
  • light:power=* - What is the electrical power (measured in Watt) of this light source (of a single light source, in case there are several light sources mounted on the same construction)?
  • light:flux=* - What is the total luminous flux (measured in Lumen) of this light source (of a single light source, in case there are several light sources mounted on the same construction)?
  • light:height=* - What is the (estimated) height of the light source above ground? Use height=* for the height of the overall construction.

Combination with existing / general tags

  • operator=* - Which company operates this light source?
  • ref=* - What is the reference number of this light source?
  • height=* - What is the height of the overall construction? Use light:height=* for the height in which the lamp is mounted.
  • colour=* - What is the colour of the overall construction? For the colour of the light, use light:colour=*.
  • support=* - How is the light source mounted? This replaces the previously used lamp_mount=* and unifies the tagging with amenity=clock.
    • support=pole - The light source is mounted on a pole (common for street lamps and floodlights).
    • support=wire - The light source is hanging from a wire (also used for street lamps, the wire often crosses the street).
    • support=wall_mounted - The light source is mounted on a wall (common for lighting at industrial buildings).
    • support=ground - The light source is standing on the ground (common for floodlights directed upwards at buildings).
    • support= - Other support structures similar to amenity=clock.

Examples

Litpath.jpg

+

Newandoldstreetlights.jpg

Na-light.jpg

Straßenlaterne.JPG

Gas lamp in Rathenow.jpg

Floodlights.jpg

Plq-runway.jpg

AircraftWarningLightChangzhou.jpg

Seaman send Morse code signals.jpg

Affected features / tags

highway=street_lamp
To be interpreted in the same way as light_source=lantern. The secondary tags from this proposal may also be used on lanterns tagged as highway=street_lamp in order to give more detailed information on their properties.
lamp_mount=*
To be replaced by support=*.
lit=yes
This tag remains unchanged; its information is simply enhanced by the exact location of lamps.
lit=sunset-sunrise
The values sunset and sunrise, which have been taken from opening_hours=*, should be enhanced by the new values dusk and dawn, since street lamps (and other light sources) are usually not switched exactly at sunset / sunrise, but some time during dusk / dawn. The values sunset / sunrise should be used only for exact times corresponding to sunset / sunrise, while dusk / dawn should be used if the switching occurs during some not exactly specified time during dusk / dawn.

Some special tags for gas lamps are in use in Düsseldorf. These should be interpreted or gradually be replaced as follows, so that in any case the contained information is preserved:

lamp_type=gaslight
To be replaced by light:method=gas.
lamp_flames=*
To be replaced by light:flames=*.
lamp_model=*
To be replaced by lantern=*.
lamp_operator=*
To be replaced by operator=*. It should be clear from the primary tag light_source=lantern that the operator applies to this lantern.
lamp_ref_swd=*
To be replaced by ref=*. It should be clear from the primary tag light_source=lantern that the ref applies to this lantern.

These changes should be implemented in maps which make use of the affected tags and editors. Tagging presets for JOSM will be provided as soon as the tagging has been agreed upon.

Rendering

Lamp symbol/different lamp symbols for different lamp types (not part of this proposal).

Comments

Please use the discussion page for comments.