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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.

This specification explains, how obstacle elevations and heights 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 element.
• The absolute height of the obstacle is encoded in the verticalStructurePart itself
• The unit of measurement is required and shall be coded as an attribute of the elevation element.
• In relation to the elevation a verticalDatum and a verticalAccuracy may be coded in addition.

Multi-Part Obstacles

A multi-part obstacle is a vertical structure that is composed from multiple parts.

• For each part the top elevation shall be encoded with the corresponding horizontalProjection of its part element
• For each part the verticalExtent may be encoded.
• The unit of measurement is required and shall be coded as an attribute of its element (elevation repectively verticalExtent)
• In relation to the elevation a verticalDatum and a verticalAccuracy may be coded in addition.

The example blow demonstrates the coding of

• the elevations P1 and P2 of the building and the elevation of the antenna on top
• the vertical extents P1 and P2 of the building and the antenna on top

Please note that the heights P1 and P2 above ground currently cannot be coded. Coding of heights will be enabled with the introduction of AIXM 5.2

Coding Rules

Coding Examples

		<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>
							...

		<!-- 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>
							...