Introduction

The AIXM model allows to code both obstacles composed of a single block and obstacles composed of multiple blocks (parts). The decision to code an obstacle as a single part or with multiple parts is taken by the data originator. Specific guidance is provided in the TOD Manual.

For example, a building with an antenna on top may be coded as a single part obstacle. In this case, a unique VerticalStructurePart is necessary, as indicated in the mapping diagram below.

The same building could also be coded as an obstacle with two parts - separated into the building itself and the antenna on top. In that case, two VerticalStructurePart are used, as indicated in the diagram below. Each has its own geometrical properties, such as horizontal projection, elevation at the top and vertical extent.

The size of the footprint varies, in many cases, with growing height (trees, tilted roofs, on-top structures, nested buildings or roof mounted antennae). It is expected that, in several cases, the application of the footprint and the maximum height, impact the obstacle clearance because the complex arrangement of such an object is much bigger than the real-world object. In such cases where the description of the object is not optimal (by footprint and height/elevation), the application of vertical segmentation may provide operational benefits. The application rules of vertical segmentation can be found in EUROCAE ED-98C. Once the relevant footprint penetrating the obstacle collection surface is known, the minimum bounding box is calculated and the dimension of each axis determined (i.e. length, width) as described in EUROCAE ED-98C Appendix G.

The segmentation of the obstacle into parts also gives the possibility to provide separately the vertical extent of each part, as shown in the figure below. The obstacle composed is P1 (i.e. the building) and P2 (i.e. the mounted antenna).

In AIXM such as case is encoded as a VerticalStructure with several VerticalStructurePart.

Example 1: Building with Supra Structures

		<!-- 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>
					...
					<!-- properties of the overall structure -->
					...
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0007-1">
 						     ...
						     <!-- properties of the first part (building) -->
							 ...
						</aixm:VerticalStructurePart>
					</aixm:part>

					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0007-2">
 						     ...
						     <!-- properties of the second part (antenna) -->
							 ...
						</aixm:VerticalStructurePart>
					</aixm:part>
				</aixm:VerticalStructureTimeSlice>
			</aixm:timeSlice>
		</aixm:VerticalStructure>
	</message:hasMember>

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