Proposal:Aviation Obstacle Light
|Aviation obstacle light|
|Proposal status:||Proposed (under way)|
|Definition:||A light indicating the presence of an object which is dangerous to an aircraft in flight.|
Aviation obstacle lights, also called obstruction lights or aircraft warning lights, are devices that are attached to tall structures and are used as collision avoidance measures. Such devices make structures more visible to passing aircraft and are usually used at night, although they may be used during the day as well. These lights need to be of sufficient brightness in order to be visible for miles around the structure.
Per International Civil Aviation Organization (ICAO) obstacle light requirements, all structures exceeding 45 meters above ground level must be appropriately marked with warning lights or paint. FAA and similar bodies may impose more specific national requirements.
This proposal aims to define how warning lights on aviation obstacles could be tagged with the new feature aeorway:light. The proposal also shows how visual markers may be tagged.
The obstacles themselves are tall vertical structures such as buildings, towers, masts, chimneys, bridges etc. They are typically tagged with man_made=*, power=*, building=* etc, or even a aeroway=navigationaid or other aeroway objects. The aeroway:light tags may preferably be put on the node or area which already represents such a structure, so that the supporting structure is also identified. Alternatively, it may be put on a separate node if a special location for the light is required or if the supporting structure is not known.
Although several lights are often required to light a tall structure, only one instance of aeroway:light is needed on each structure. If the structure in question is particularly wide, such as an oil refinery, a chemical plant or a bridge, then one or more extra locations may be tagged with aeroway:light in order to illustrate the horizontal scope of the structure. If an official aviation obstacle database is the source, such as the FAA Digital Obstacle File (DOF), then there will already be a suggestion on which locations to map for these scenarios.
Aviation obstacle lights are conspicious features of tall structures. Obstacle lights in OSM may be used by flight simulators. When using external open sources for aviation obstacles for mapping for example communication masts, the structures may get a more complete description using this new key. There is currently no definition on how to tag these warning lights except for seamark tagging for the specific need of nautical charts.
The tagging schema is based on the requirements given by ICAO and FAA, and on the Aeronautical Information Exchange Model (AIXM). It is deliberately similar to seamark tagging for lights, which is standardized by IHO/IALA and which has proven flexible for a variety of scenarios. Details of the lights are tagged with the aeroway:light: prefix. The tagging schema has been designed to also be applicable for other aeronautical light objects such as aerodrome beacons.
|aeroway:light||obstacle||There is an obstacle light on the structure. If no other information known then this will be the only tagging. Mandatory for obstacles.|
||Colour of the light.
A combination of two colours may be used to denote alternate flashing of these colours, for example white;green.
|aeroway:light:character||fixed||Steady light; a signal light that shows continuously, in any given direction, with constant luminous intensity and colour|
|flashing||Strobe light; a rhythmic signal light alternating between light and darkness|
|floodlight||A broad beam light used to illuminate a structure or area (less common than fixed and flashing)|
|aeroway:light:intensity||high||High intensity light as defined by ICAO and FAA, typically 200,000+ candela. Typically added based on external sources rather than measured by mapper.|
|medium||Medium intensity light as defined by ICAO and FAA, typically around 20,000 candela. Typically added based on external sources rather than measured by mapper.|
|low||Low intensity light as defined by ICAO and FAA, typically 2,000 candela or less. Typically added based on external sources rather than measured by mapper.|
||Light categories as defined by ICAO (type D is for follow-me vehicles, so not likely to be mapped in OSM)|
|aeroway:light:multiple||*||The number of obstacle objects of identical type and with lights of identical character that exists as a co-located group. Optional. Do not use if there is only one obstacle object.|
|height||*||Vertical height of the lighted structure (in meters)|
|ele||*||Elevation above sea level at the foot/ground level of the lighted structure (in meters)|
Use the :conditional suffix to tag dual lights with one colour/intensity etc at night and a different during daylight, e.g. aeroway:light:colour=white@sunrise-sunset and aeroway:light:colour=red@sunset-sunrise.
Visual marking on the structure may be tagged in this way:
|aeroway:marking||obstacle||The structure is painted or has other visual markers to warn aircrafts. If no other information known then this will be the only tagging. Mandatory.|
|aeroway:marking:type||paint||The obstacle may be painted to make it conspicuous to pilots.|
|flag||Flags are used to mark certain structures or objects when it is technically impractical to use spherical markers or paint. Some examples are temporary construction equipment, cranes, derricks, oil and other drilling rigs.|
|sphere||The spherical marker balls are typically attached to catenary structures/suspended wires. In this case, the way between the two supporting structures may already have been tagged with for example power=line between two power=tower nodes and may get additional tagging according to this table.|
||Colour of the paint or marker.
A combination of two or more alternating colours may be used, for example white;orange.
|aeroway:marking:pattern||horizontal||The object is marked with horizontal colour bands.|
|vertical||The object is marked with vertical colour bands.|
|chequered||Often referred to as checker plate, where alternate colours are used to create squares similar to a chess or draught board.|
ICAO obstacle light types
|iCAO intensity type||ICAO light type||Key/value||Comments|
|Low intensity||Type A||aeroway:light:colour=red|
|Type C||aeroway:light:colour=yellow (or blue)||For mobile vehicles, not likely to be mapped in OSM|
|Type D||aeroway:light:colour=yellow||For follow-me vehicles, not likely to be mapped in OSM|
|Medium intensity||Type A||aeroway:light:colour=white|
|HIgh intensity||Type A||aeroway:light:colour=white|
FAA obstruction light types
|DOF light code||DOF light type||Key/value||Comments|
|R||Red||aeroway:light:colour=red||Flashing red light|
|D||Medium intensity White Strobe & Red||aeroway:light:colour:conditional=white@sunrise-sunset
|Medium intensity flashing white (day) + red (night)|
|H||High Intensity White Strobe & Red||aeroway:light:colour:conditional=white@sunrise-sunset
|High intensity flashing white (day) + red (night)|
|M||Medium Intensity White Strobe||aeroway:light:colour=white||Medium intensity flashing white|
|S||High Intensity White Strobe||aeroway:light:colour=white||High intensity flashing white|
|F||Flood||aeroway:light:character=floodlight||The structure is illuminated by a broad floodlight|
|C||Dual Medium Catenary||aeroway:light:colour=red||Dual lighting of power line or other catenary wires|
|W||Synchonized Red Lighting||aeroway:light:colour=red||Flashing red lighting, synchronized with group of lights|
|N||Lighted (Type Unknown)||aeroway:light=obstacle||The obstacle is lighted but light type is unknown|
|U||Unknown||(none)||Lighting not known|
Please note that the elevation attribute in DOF refers to the top of the vertical structure, while ele=* refers to the ground level, i.e. the foot of the structure, so the height of the structure needs to be subtracted to derive the correct ground elevation.
|DOF mark code||DOF marking type||Key/value||Comments|
|P||Orange or Oragne and White Paint||aeroway:marking:type=paint
|The object is painted orange or orange and white.|
|W||White Paint only||aeroway:marking:type=paint
|The object is painted white.|
|M||Marked||aeroway:marking=obstacle||The object is marked, details unknown|
|F||Flag Marker||aeroway:marking:type=flag||The object is marked with a flag, details unknown|
|S||Spherical Marker||aeroway:marking:type=spherical||The object is marked with a spherical marker ball.|
|N||None||(none)||The obstacle is not marked|
|U||Unknown||(none)||Marking not known|
Other national obstacle light types
An import plan is under way for aviation obstacles in Norway, and a small pilot import has been done for the South/East part of Norway.: Aviation obstacle import Norway.
Obstacle lights could be applied to any tall structure in OSM. Typical objects would be:
Rendering only likely on maps showing aviation related objects.
The following features have been considered:
- aeroway=navigationaid - Used to describe approach navigation systems at airports, so not appropriate for obstacle lights. In the future aeroway=navigationaid may be used to describe more types of navaids. The AIXM standard defines navaids and obstacles as two different concepts. The two classes overlap, so a navaid and an obstacle may exist at the same vertical object. In this proposal the obstacle light may belong to a aeroway=navigationaid or any other aeroway object.
- Seamark lights - The obstacle light information could be used for seamark:light:category=air_obstruction objects, however it would need to be tagged with seamark tags. Obstacles which are close to the sea will often also be tagged as seamarks, so it is convenient to have a similar tagging structure for the lights.
- Proposed features/Key:light source - This proposal from 2014 has been considered but the tagging structure was not capable of denoting all characteristics for the aviation obstacles. Also, the seamark tagging schema for lights has a much higher usage. On a light mast (man_made=mast + tower_type=lighting) on for example a sports stadium, light_source could be used to describe the floodlight from the mast while aeroway:light could be used to describe the warning light for aircrafts.
- Proposed features/aeroway obstacle - This abandoned proposal from 2008 attempted to define aviation obstacles (all the structures) including lighting. It was abandoned because man_made and other keys already described these objects. In the discussion for that proposal it was suggested to tag the warning lights only. Those comments have been used when crafting the proposal for aeroway:light.
- airmark=beacon - The airmark key currently have one value only, namely beacon. On the discussion page it has been commented that the airmark key was introduced without any discussion and should be avoided.
ICAO Appendix 14 Chapter 6 - Visual Aids for Denoting Obstacles - Excerpt from the previous document
FAA Digital Obstacle File (DOF) - Please see the readme document for light categories
Please comment on the discussion page.
Voting on version 1 of this proposal was aborted and the proposal was put back into RFC on 2018-04-02 to accomodate further comments from the voting process. The main change from version 1 is to use the aeroway key instead of airmark. All comments from the voting has been copied to the discussion page.