Airspace [ASE]

AIXM Model Overview

The following AIXM UML model diagrams indicates the scope of these coding guidelines.

The main class in this AIXM model is the Airspace containing the basic data, such as the name and type of the airspace.

In addition the airspace model contains associated objects in order to encode the vertical and lateral limits of the airspace.

AIXM 5 provides several possibilities to encode the lateral limits of an airspace

The airspace class may be defined for the whole airspace or layers of it.

Furthermore, within an airspace an ATS unit may provide a service on one or more particular radio communication channel (frequency).

Airspaces and also the service provided by the ATS unit may have certain schedules.

For Special Activity Airspaces also information about the existing type of restriction or nature of hazard, activation process and/or time of activity may be provided.

Basic data (type & name)

The basic data of an Airspace are the type (e.g. 'FIR', 'CTR') and its name (e.g. 'RIGA' FIR, 'LJUBLJANA' CTR).

In addition, for some ATS airspace types such as "FIR" or "Danger Area" a designator will be encoded. In case the designator is published in the ICAO Doc 7190 also the attribute designatorICAO will be encoded accordingly with 'YES'.

In order to indicate that an airspace or area is under military, joint of civil control the controlType attribute will be used.

For ATS airspaces, which may be composed of several parts, AIXM provides a dedicated "Part" type (e.g. 'FIR-P', 'CTR-P', etc.). This allows to encode a whole ATS airspace as a composition of its parts (See Lateral Limits section below).

The following table contains some guidelines for the AIXM 5 encoding of the type of airspaces listed in PANS-AIM:

Coding guidelines for airspace types

For types of airspaces which are not specifically listed in the CodeAirspacetype class, the 'OTHER' value will be used followed by the code (abbreviation) for the local/regional type of the airspace. In such a case, in addition the localType attribute will be encoded with the full name of the local airspace type (e.g. 'OTHER:HPZ' and 'Helicopter Protected Zone').

Coding rules for basic airspace data

Vertical limits

For the encoding of the vertical limits of an airspace the AirspaceVolume class is used.

Besides the upperLimit and the lowerLimit of the airspace AIXM also provides additional attributes to encode a maximumLimit and a minimumLlimit. The latter two are not required for the AIP data set, but may be encoded by the data provider if required.

The figure below illustrates the 4 different kinds of vertical limits using some example values.

Note from the author: Figures to be updated to AIXM 5.1 values

Numerical values

Vertical limits are typically encoded in AIXM as a pair of two attributes:

• a ...Limit attribute, which includes the value and its unit of measurement (as an uom attribute) with the list of valuesUomDistanceVerticalType
• a ...LimitReference attribute, which indicates what reference system is used for the vertical limit value. It uses the following list of values:CodeVerticalReferenceType

The following consistency rules between the uom value and the reference value shall be observed when encoding the data:

Coded values (GND, UNL, etc.)

In addition to numerical values, the ...Limit" attributes can use four coded values:

• 'GND'- meaning "from surface"
• 'UNL' - meaning "unlimited"
• 'FLOOR' - meaning "from the bottom of the airspace/route, whatever that one is"
• 'CEILING ' - meaning "to the top of the airspace/route, whatever that one is"

As the unit of measurement attribute is mandatory in for the AIP data set, the following values are recommended when encoding the data:

The ...LimitReference attribute shall be left empty in this situation. However, even if another uom is used or even if the ...LimitReference attribute gets a value, they should be ignored by a recipient application because they do not have any meaning in combination with these coded values.

The figure below illustrates the encoding of Flight Level (FL), Above Mean Sea level (AMSL) and Above Ground Level (AGL).

Note from the author: Figures to be updated to AIXM 5.1 values

Coding rules for vertical limits

Coding rules for class of airspace

Lateral Limits

There are two main ways to describe the geometry of airspace volumes in AIXM:

• by providing a horizontal border and vertical limits;
• by providing a composition rule by which the airspace is defined as a series of unions, intersections, subtractions of other Airspace, such as in the following examples:
  • Airspace of type CTR defined as a “circle of 50 NM from which the portion of airspace situated in a neighboring FIR is subtracted”;
  • Airspace of type UIR that has “the same horizontal projection as an FIR”, but different vertical limits;
  • Airspace of type CTA which is the result of aggregating some Airspace of type SECTOR;
  • etc.

The AirspaceVolume class of the AIXM 5 model was designed in order to support the encoding of such aggregated Airspace. Note that the “operation” property of the AirspaceGeometryComponent is used.

The model gives the possibility for using several approaches for the encoding of airspace aggregations/dependencies. The use of a particular method, from the ones described further in this section, depends on the intended use of the data. Details encoding description of the GML elements used by AIXM 5 can be found in OGC® document: 12-028r1 "Use of Geography Markup Language (GML) for Aviation Data".

Airspace geometry by horizontal border

Airspace geometry - One AirspaceVolume

Airspace geometry by composition (more than one AirspaceVolume)

Types for Airspace Geometry Components

AirspaceGeometryComponent.operation

'UNON'

'SUBSTR'

'INTERS'

More than one AirspaceVolume

Option 1a: coping geometry

Option 1b: “pure geometry components”

Option 2: referencing

Geoborder & Significant Point

Geoborder

Airspace boundaries may be based on national borders or on other geographical features, such as shorelines, rivers, etc.

A particularity of this situation is that official definitions of the airspace, as provided in the Aeronautical Information Publication (AIP) or in NOTAM messages, do not include the actual geometry of the referenced geographical border. It is left for the end users to derive the actual geometry of the airspace by using a source of geographical border data.

The UML model of AIXM shows a “dependency” association between Surface and GeoBorder in order to cater for such situations

The encoding is possible in two ways: either with a simple annotation (and copy of all necessary points) or by reference. See the AIXM GML Guidelines for details.

Significant Point

Coding rules for lateral limits

Class of airspace

For ATS airspaces PANS-AIM requires the class of airspace.

In AIXM 5 the class of airspace is encoded by the using the AirspaceLayerClass.classification attribute. The codeAirspaceClassificationType contains a list of value for all classes (A-G).

In AIXM it is possible to encode one class for the whole airspace but also different classes for several layers within an airspace. For the latter the AirspaceLayer class is used.

The airspace layer concept is also used for the activation of Special activity airspaces which may be activated for just a partcular layer of  their whole vertical dimension (see Digital NOTAM Specification).

Transition Altitude

ICAO Annex 15 defines Transition altitude as follows:

The altitude at or below which the vertical position of an aircraft is controlled by reference to altitudes.

According to PANS-AIM the transition altitude is only required for airspaces listed in section "AD 2.17 ATS airspace" (e.g. CTR).

ATS Unit providing Service

Restriction & Activation

Hours of applicability / Hours of Service / Time of acitivity

In PANS-AIM different data items are defined for Schedules which are relevant for an airspace or a unit providing service within an airspace.

For ATS airspace, Appendix 1 of PANS-AIM (Aeronautical Data Catalogue) defines the "Hours of applicabiliy" for the airspace and in addtion the "Hours of Service", which are "the operational hours of the station serving the unit".

However, in an AIP the first item is only published for ATS airspaces of section AD 2.17, whereas the latter is only published for ATS airspaces listed in section ENR 2.1.

For Special activity airspaces the "Time of activity" is defined as "Time interval when the special activity takes place".

In the following only those coding rules specfic to the airspace subjects will be discussed. 

For the general coding guidelines for the Timesheet refer to Schedule.

Hours of applicabiliy

This information is required for ATS airspaces usually published in "AD 2.17 Air traffic services airspace":

6) hours of applicability;

In AIXM this information will be encoded as Airspace.activation.

Hours of Service

This information is required for ATS airspaces usually published in "ENR 2.1 FIR, UIR, TMA AND CTA":

3) call sign of aeronautical station serving the unit and language(s) used, specifying the area and conditions, when and where to be used, if applicable;

In AIXM this information will be encoded as Service.availability.

Time of activity

This information is required for Sepecial activity airspaces usually published section in "ENR 5":

In AIXM this information will be encoded as Airspace.activation.

Coding Rules for

Coding Examples

Coding Example can be found in the AIXM DONLON ACGAIP file.

Additional Illustrated Coding Examples

Example: Sand Springs

Example: Twin Peaks

References