Introduction

In AIXM 5.1.x vertical dimensions of obstacles can be coded as the vertical extent of each obstacle part and the elevation on top of each part:

  • the vertical extent is the vertical distance from the bottom to the top of the part itself; on a single part obstacle the vertical extant is the height from the ground to the top of the obstacle. It is coded in the VerticalStructurePart.verticalExtent attribute.
  • the elevation is the MSL elevation of the topmost point of each part. Depending on the part's geometry, the elevation is coded in ElevatedSurface.elevation attribute for polygons, in the ElevatedCurve.elevation attribute for line obstacles or in the ElevatedPoint.elevation attribute for line obstacles.


Currently it is not possible to code the height of an obstacle part above ground. Since the coding of heights is required by the ICAO Annex 15 and the industry standards (RTCA/EUROCAE DO-276 /ED-98) an AIXM change request is already in progres to fix this issue.


This specification explains, how obstacle elevations shall be coded in AIXM.


Single Part Obstacles

A single part obstacle is a vertical structure that is coded as only one part,


The top elevation of the obstacle is encoded with the corresponding horizontalProjection of its part(s) element.

A unit of measurement is required.

In relation to the elevation a verticalDatum and a verticalAccuracy may be coded in addition.

		<aixm:VerticalStructure gml:id="uuid.5f68d835-828c-4ccd-91b7-791058d9dd4d">
			<gml:identifier codeSpace="urn:uuid:">5f68d835-828c-4ccd-91b7-791058d9dd4d</gml:identifier>
			...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="V-af4ee6d6">
							...
							<aixm:horizontalProjection_location>
								<aixm:ElevatedPoint srsName="urn:ogc:def:crs:EPSG::4326" gml:id="p1121">
									...
									<!-- elevation required by PANS-AIM Table A6-2 "Elevation" and ENR 5.4,AD 2/3.10 -->
									<aixm:elevation uom="M">150</aixm:elevation>
									<aixm:verticalDatum>EGM_96</aixm:verticalDatum>
									<aixm:verticalAccuracy uom="M">30</aixm:verticalAccuracy>
								</aixm:ElevatedPoint>
							</aixm:horizontalProjection_location>
							...

The top elevation of an obstacle is encoded with the corresponding horizontalProjection of its part(s) element.

A unit of measurement is required.

In relation to the elevation a verticalDatum and a verticalAccuracy may be coded in addition.

Example 1: Elevation - Single Part Obstacle

The example below shows the encoding of the elevation of a single part obstacle.

		<aixm:VerticalStructure gml:id="uuid.5f68d835-828c-4ccd-91b7-791058d9dd4d">
			<gml:identifier codeSpace="urn:uuid:">5f68d835-828c-4ccd-91b7-791058d9dd4d</gml:identifier>
			...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="V-af4ee6d6">
							...
							<aixm:horizontalProjection_location>
								<aixm:ElevatedPoint srsName="urn:ogc:def:crs:EPSG::4326" gml:id="p1121">
									...
									<!-- elevation required by PANS-AIM Table A6-2 "Elevation" and ENR 5.4,AD 2/3.10 -->
									<aixm:elevation uom="M">150</aixm:elevation>
									<aixm:verticalDatum>EGM_96</aixm:verticalDatum>
									<aixm:verticalAccuracy uom="M">30</aixm:verticalAccuracy>
								</aixm:ElevatedPoint>
							</aixm:horizontalProjection_location>
							...

Example 2: Elevation - Multi Part Obstacle

In case of multi-part obstacles the top elevation of each part is coded.

As in the following example the elevation of the building and the elevation of the Antenna on top is provided.


		<!-- POINT ON SURFACE: roof mounted antenna (Vertical Segmentation: 2 parts)-->
		<aixm:VerticalStructure gml:id="uuid.15c2c2ba-c5f2-47b5-9ada-1964d51b82c0">
			<gml:identifier codeSpace="urn:uuid:">15c2c2ba-c5f2-47b5-9ada-1964d51b82c0</gml:identifier>
			...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0007-1">
							...
							<aixm:horizontalProjection_surfaceExtent>
								<aixm:ElevatedSurface srsName="urn:ogc:def:crs:EPSG::4326" gml:id="ep0007-1">
									<gml:patches>
										<gml:PolygonPatch>
											<gml:exterior>
												<gml:Ring>
													<gml:curveMember>
														<gml:Curve gml:id="c4567">
															<gml:segments>
																<gml:GeodesicString>
																	<gml:posList>55.5243055555556 -24.64125833333333 
																		55.5201388888889 -24.63178888888889 
																		55.5211666666667 -24.63032222222222 
																		55.5251944444444 -24.63868888888889 
																		55.5243055555556 -24.64125833333333</gml:posList>
																</gml:GeodesicString>
															</gml:segments>
														</gml:Curve>
													</gml:curveMember>
												</gml:Ring>
											</gml:exterior>
										</gml:PolygonPatch>
									</gml:patches>
									...
									<aixm:elevation uom="M">168</aixm:elevation>
									<aixm:verticalDatum>EGM_96</aixm:verticalDatum>
									<aixm:verticalAccuracy uom="M">30</aixm:verticalAccuracy>
								</aixm:ElevatedSurface>
							</aixm:horizontalProjection_surfaceExtent>
							...
						</aixm:VerticalStructurePart>
					</aixm:part>
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0007-2">
							...
							<aixm:horizontalProjection_location>
								<aixm:ElevatedPoint srsName="urn:ogc:def:crs:EPSG::4326" gml:id="VID000005">
									<gml:pos>55.52416667 -24.63888889</gml:pos>
									...
									<aixm:elevation uom="M">191</aixm:elevation>
									<aixm:verticalDatum>EGM_96</aixm:verticalDatum>
									<aixm:verticalAccuracy uom="M">30</aixm:verticalAccuracy>
								</aixm:ElevatedPoint>
							</aixm:horizontalProjection_location>
							...