Obstacle type

Introduction

The obstacle type is usually provided with a descriptive noun, such as 'building', 'bridge', 'antenna', 'tree', etc. In AIXM 5.1(.1), the type can be coded at two levels:

• for the obstacle as a whole, using the VerticalStructure.type
• for each of its components, using the VerticalStructurePart.type

For aeronautical operations, the type is not considered a critical property when the geometry of the obstacle is coded in detail, using the possibilities offered by the AIXM model.  It is mostly used for identifying the obstacle, either visually or when comparing obstacle data sources for the same area. For certain types, such as 'tree', 'vegetation', etc. the type is also an indication that the height of the obstacle evolve in time and might be a hint for verifying the date when the data was collected.

Only when the geometry is coded in a simplified way the type provides additional information for the data users. For example, when a power line that is coded as a single position, the type is important because it is the only property that indicates that the horizontal/vertical extent is larger than the single position.

AIXM 5.1(.1) provides a predefined list of values for obstacle types, which was derived from several sources:

• EUROCAE ED-98 / RTCA DO-276 / User Requirements for Terrain and Obstacle data ;
• real-world data, based on data samples provided by the United States National Geospatial Agency (NGA);
• additional types derived from standards previously developed by the Air Modelling Advisory Team (Air MAT) and based on the model for FAA’s Electronic Airport Layout Plan (eALP).

This limited list of values aims at providing some uniformity in the identification of the obstacle types in the digital data sets, while the current AIP and other obstacle data sources contain a significantly larger number of terms that are used.

The following table indicates the current list of obstacle types. 

Coding guidelines

For single part obstacles, the type shall be coded only in the VerticalStructure.type.

For multi-part obstacles, the type shall be coded always in the VerticalStructure.type. In addition, if a part has a different type from the overall obstacle, then the specific type of the may be coded in the VerticalStructurePart.type. There are certain plausibility rules that can be verified - for example, it does not make sense for a VerticalStructure with type='VEGETATION' to have VerticalStructurePart.type with values such as 'BULDING', 'MONUMENT'. etc. However, it is not possible to provide very precise rules with regard to the overall type based on the type of the parts. The type value, both for the parts and the overall obstacle, need to be decided by the data originator.

Coding Examples

Single Part Obstacle

In this example, the obstacle type is coded ('ANTENNA') only in the VerticalStructure.type. 

		<aixm:VerticalStructure gml:id="uuid.5f68d835-828c-4ccd-91b7-791058d9dd4d">
			<gml:identifier codeSpace="urn:uuid:">5f68d835-828c-4ccd-91b7-791058d9dd4d</gml:identifier>
			...
					<!-- type required by PANS-AIM Table A6-2 and ENR 5.4, AD 2/3.10. For single part obstacles, it shall be coded only in the VerticalStructure -->
					<aixm:type>ANTENNA</aixm:type>
					...

Multi Part Obstacle

In this example, each VerticalStructurePart has its own type ('BUILDING' or 'CATENARY'), which is different from the overall VerticalStructure.type ('CABLE_CAR').

		<aixm:VerticalStructure gml:id="uuid.87a585b3-0597-4f5c-974f-cddfc604dc93">
			<gml:identifier codeSpace="urn:uuid:">87a585b3-0597-4f5c-974f-cddfc604dc93</gml:identifier>
			...
					<aixm:type>CABLE_CAR</aixm:type>
					...
					<!-- PART1: LANGTALERECKHUETTE (Ground Station) of Cable Way -->
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0004-1">
							...
							<aixm:type>BUILDING</aixm:type>
							...
					</aixm:part>
					<!-- PART2: Line (rope) between Ground Station and Top Station -->
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0004-2">
							...
							<aixm:type>CATENARY</aixm:type>
							<...
					</aixm:part>
					<!-- PART3: HOCHWILDEHAUS (Top Station) of Cable Way -->
					<aixm:part>
						<aixm:VerticalStructurePart gml:id="vsp0004-3">
							...
							<aixm:type>BUILDING</aixm:type>
							...
					</aixm:part>
				</aixm:VerticalStructureTimeSlice>
			</aixm:timeSlice>
		</aixm:VerticalStructure>

The following coding examples can be found in the Obstacle Data Set - Specimen (DONLON):