Obstacle lighting

The requirements for obstacle lighting are described in:

ICAO 9157 - Aerodrome Design Manual, Part 4 - Visual Aids, Chapter 15 - Marking and lighting of obstacles
Annex 14, Volume I, Chapter 6-Visual aids for denoting obstacles, Table 6-1

According to ICAO, obstacle lights emit either white or red light, except for mobile obstacles where blue light may be used. However in some AIP yellow light is also present on obstacles.
Some types of lights provide a steady signal, other types have a flashing characteristic. Depending on the particular application and required visual range (day/twilight/night), low-, medium- or high-intensity lights are used.

Model Overview

The UML class diagram below shows the main AIXM 5.1(.1) classes used to model the lighting associated with a vertical structure.

In addition to the overall indication that the obstacle is lighted, provided by the VerticalStructure.lighted attribute, a set of classes associated with the VerticalStructurePart allow for detailing the lighting data.

The main element of this model is the LightElement class, which has properties such as colour, intensityLevel, etc. that model the physical characteristics of each light source situated on the obstacle. The hasPosition association between LightElement and ElevatedPoint allows to indicate the exact location, horizontal and vertical, of the light element. A VerticalStructurePart may be associated with zero of more LightElement.

The operating hours of the obstacle lighting or the eventual unserviceability of the obstacle lighting is modelled at two levels:

the association lightingIsOperational between VerticalStructure and VerticalStructureLightingStatus allows to indicate the overall status and operating hours of the obstacle lighting (all lights together);
for each LightElement, the association isOperational with LightElementStatus allows indicating the operational status and operating hours of the individual light element.

AIXM 5.2 Improvement

A change proposal (AIXM-521) for the next AIXM 5.2 version has been approved by the AIXM Change Control Board, which adds an additional attribute to LightElement to allow for identification of specific lighting technology.

The coding guidelines provided here are aligned with forward/backward conversion rules contained in the AIXM-521 Change Proposal.

AIXM 5.2 Improvement

A change proposal (AIXM-517) for the next AIXM 5.2 version has been approved by the AIXM Change Control Board, which adds an additional attribute to LightElement to indicate the direction of the lighting.

The coding guidelines provided here are aligned with forward/backward conversion rules contained in the AIXM-517 Change Proposal.

Coding Guidelines

The PANS-AIM Data Catalogue further details the lighting into lighting type and lighting colour.

The lighting type is coded using the VerticalStructurePart.lighting.LightElement.type element. For example, a flashing light can be encoded using for type = 'STROBE'
The lighting colour is coded using the VerticalStructurePart.lighting.LightElement.colour element.

In relation with the lighting status, there exist two particular situations that could be using obstacleLight.status:

Autonomous aircraft detection system: may be installed on or near an obstacle (or group of obstacles such as wind farms), designed to operate the lighting only when the system detects an aircraft approaching the obstacle, in order to reduce light exposure to local residents. This can be coded with status = 'OTHER:ACFT_DETECTION' - the lighting is activated by an aircraft detection system. Details about the aircraft detection system used (for example, Mode S and Mode A + C transponder emissions in close proximity) can be coded as an annotation.Note with purpose = 'DESCRIPTION' and property = 'status'.

Dynamic obstacle lighting: the obstacles have lighting that can be switched on or off from distance in function of operational requirements (e.g. military low-level training flights). This can be coded with status = 'OTHER:DYNAMIC' - the lighting is activated dynamically, when required operationally. No specific schedule.

AIXM 5.1(.1) Limitation

The current model is lacking the possibility to indicate that e light source is based on LED technology. This is of particular importance for certain nigh-vision systems and head-up displays that are unable to see the LED lights. This issue has been raised in the AIXM CCB and it is expected to be resolved in the next AIXM 5.2 version.

Example 1: Unlighted Obstacle

The example below shows how to encode that an obstacle is not lighted.

Example 1: Unlighted Obstacle

		<!-- SINGLE PART OBSTACLE (Natural Highpoint) -->
		<aixm:VerticalStructure gml:id="uuid.cd0bfb54-81b9-491e-880b-7f85fe2dbfb8">
			<gml:identifier codeSpace="urn:uuid:">cd0bfb54-81b9-491e-880b-7f85fe2dbfb8</gml:identifier>
			...
					<aixm:type>NATURAL_HIGHPOINT</aixm:type>
					<aixm:lighted>NO</aixm:lighted>

Example 2: Lighted Obstacle

The example below shows how to encode that an obstacle is lighted (without any further details).

Example 2-1: Lighted Obstacle (simple)

		<!-- SINGLE PART OBSTACLE (Crane) -->
		<aixm:VerticalStructure gml:id="uuid.df421db4-3698-4003-9d71-93ca57e70ffc">
			<gml:identifier codeSpace="urn:uuid:">df421db4-3698-4003-9d71-93ca57e70ffc</gml:identifier>
			...
					<aixm:type>CRANE</aixm:type>
					<aixm:lighted>YES</aixm:lighted

The example below shows how to encode that an obstacle is lighted, with further details, including type and colour of lighting.

Example 2-2: Lighted Obstacle with further Details

		<!-- WINDPARK -->
		<aixm:VerticalStructure gml:id="uuid.499c5bb4-de1e-49fc-8db1-11ffa84406d6">
			<gml:identifier codeSpace="urn:uuid:">499c5bb4-de1e-49fc-8db1-11ffa84406d6</gml:identifier>
			...
					<aixm:type>WINDMILL_FARMS</aixm:type>
					<aixm:lighted>YES</aixm:lighted>
					...
					<aixm:lightingICAOStandard>YES</aixm:lightingICAOStandard>
					<aixm:synchronisedLighting>YES</aixm:synchronisedLighting>
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0002-9">
							...
							<aixm:lighting>
								<aixm:LightElement gml:id="le00022-1">
									<aixm:colour>RED</aixm:colour>
									<aixm:intensityLevel>LIM</aixm:intensityLevel>
									<aixm:type>OTHER:FLASHING</aixm:type>
								</aixm:LightElement>
							</aixm:lighting>
						</aixm:VerticalStructurePart>
					</aixm:part>

Example 3: Lighted Obstacle with Day and/or Night Indication

To indicate that an obstacle is ligted during day and/or night, in principle there a 2 options, either using a Timesheet or a Note.

The examples below shows 2 VerticalStructure features one with a timesheet and the other one with an annotation.

Example 3-1: Lighted Obstacle Day and/or Night (Timesheet)

		<!-- SINGLE POINT OBSTACLE. -->
		<aixm:VerticalStructure gml:id="uuid.5f68d835-828c-4ccd-91b7-791058d9dd4d">
			<gml:identifier codeSpace="urn:uuid:">5f68d835-828c-4ccd-91b7-791058d9dd4d</gml:identifier>
			...
					<aixm:type>ANTENNA</aixm:type>
					<aixm:lighted>YES</aixm:lighted>
					...
					<!-- lightingICAOStandard and synchronisedLighting is not explicitly required by PANS-AIM -->
					<aixm:lightingICAOStandard xsi:nil="true" nilReason="unknown"/>
					<aixm:synchronisedLighting xsi:nil="true" nilReason="unknown"/>
					...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="V-af4ee6d6">
							...
							<aixm:lighting>
								<aixm:LightElement gml:id="le0001">
									<!-- PANS-AIM table A-6-2 only requires information if an obstacle is lighted. 
										However, colour and type are properties listed in the PANS-AIM Appendix 1 "Aeronautical Data Catalogue" and ENR 5.4, AD2/3.10. 
										intensityLevel, intensity and availability is not explicitly required by PANS-AIM -->
									<aixm:colour>RED</aixm:colour>
									<aixm:intensityLevel xsi:nil="true" nilReason="unknown"/>
									<aixm:intensity xsi:nil="true" nilReason="unknown"/>
									<aixm:type xsi:nil="true" nilReason="unknown"/>
									<!-- regarding availability, see also lightingAvailability  -->
									<aixm:availability xsi:nil="true" nilReason="inapplicable"/>
								</aixm:LightElement>
							</aixm:lighting>
							...
					<!-- lightingAvailability not explicitly required by PANS-AIM 
					Coding of the availability meaning lighted during Night. May also be coded as annotation.
					(NOTE: There is also the availability property for the LightElement of the VerticalStructurePart, 
					OPEN QUESTION: Should there be a rule that it shall only be used in case the availability of the lighting schedule is different for one or more parts.) -->
					<aixm:lightingAvailability>
						<aixm:VerticalStructureLightingStatus gml:id="vsls02012">
							<aixm:timeInterval>
								<aixm:Timesheet gml:id="ts022">
									<aixm:day>ANY</aixm:day>
									<aixm:dayTil>ANY</aixm:dayTil>
									<aixm:startEvent>SS</aixm:startEvent>
									<aixm:endEvent>SR</aixm:endEvent>				
								</aixm:Timesheet>
							</aixm:timeInterval>
							<aixm:specialDateAuthority xsi:nil="true" nilReason="inapplicable"/>
							<!-- OPEN QUESTION: is status required (i.e. for Digital NOTAM)? -->
							<aixm:status>NORMAL</aixm:status>
						</aixm:VerticalStructureLightingStatus>
					</aixm:lightingAvailability>
					</aixm:VerticalStructureTimeSlice>
			</aixm:timeSlice>
		</aixm:VerticalStructure>

Eample 3-2: Lighted Obstacle Day and/or night (Note)

		<!-- GROUPS OF OBSTACLES GROUPED WITH AN AREA (POLYGON) (Windfarm area).
			Case where a large number of obstacles with similar elevation are grouped, an area encompassing the grouped obstacles may be published instead of publishing each individual object.-->
		<aixm:VerticalStructure gml:id="uuid.47db48e9-d46a-4100-a266-25a3968b6a98">
			<gml:identifier codeSpace="urn:uuid:">47db48e9-d46a-4100-a266-25a3968b6a98</gml:identifier>
			...
					<aixm:type>WINDMILL_FARMS</aixm:type>
					<aixm:lighted>YES</aixm:lighted>
					<aixm:markingICAOStandard>NO</aixm:markingICAOStandard>
					...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0002-1">
							...
							<aixm:lighting>
								<aixm:LightElement gml:id="le0002-1">
									<aixm:colour>RED</aixm:colour>
									<aixm:intensityLevel>LIM</aixm:intensityLevel>
									<aixm:type>OTHER:FLASHING</aixm:type>
								</aixm:LightElement>
							</aixm:lighting>
						</aixm:VerticalStructurePart>
					</aixm:part>
					<!-- The information that the lighting is provided 'day' or 'night' or 'day and night' may be coded as annotation or also
						with as dedicated availability (timesheet) using e.g. from Sunset (SS) to Sunrise (SR) or vice versa, or similar. -->
					<aixm:annotation>
						<aixm:Note gml:id="n12-13">
							<aixm:propertyName>lighted</aixm:propertyName>
							<aixm:translatedNote>
								<aixm:LinguisticNote gml:id="ln12-13">
									<aixm:note lang="eng">day and night</aixm:note>
								</aixm:LinguisticNote>
							</aixm:translatedNote>
						</aixm:Note>
					</aixm:annotation>
					...