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Description

The data type for verticalDatum attribute of AirportHeliport, ElevatedCurve, ElevatedPoint, ElevatedSurface is changed to ValVerticalDatumType (using URI values).

Rationale for change

https://aixmccb.atlassian.net/browse/AIXM-173

It was identified that the current list of values of CodeVerticalDatumBaseType used in verticalDatum attribute of AirportHeliport, ElevatedCurve, ElevatedPoint, ElevatedSurface is insufficient to cover the current needs of indicating vertical reference systems.

It is proposed that the data type CodeVertical(Base)Type is replaced with a data type ValVerticalDatumType as a specialisation of anyURI data type to support a growing number of vertical reference datums used worldwide.

The encoding rules will be described in a respective section of Coding Guidelines.

Impact assessment

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[FWD_MAP_1:1] “Data mapping is possible and no data loss occurs when data is exchanged from a system (A) that uses AIXM 5.1.1 for output towards a system (B) that uses AIXM 5.2 for input.”

[BWD_MAP_1:1] “Data mapping is possible and no data loss occurs when data is exchanged from a system (B) that uses AIXM 5.2 for output towards a system (A) that uses AIXM 5.1.1 for input”

Change Proposal details

In the UML model, in AirportHeliport feature and ElevatedCurve, ElevatedPoint, ElevatedSurface objects :

• For attribute verticalDatum
  • change data type to TextNameType.

In the UML model:

• Delete CodeVerticalDatumBaseType and CodeVerticalDatumType data types.

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Mapping AIXM 5.1.1 to AIXM 5.2 (forward)

[MAPC-01/MAPC-02 (derivative)]

The following algorithm shall be applied:

• For each AirportHeliport, ElevatedCurve, ElevatedPoint, ElevatedSurface.verticalDatum
  • If value = ‘EGM_96’, then replace it with ‘urn:ogc:def:datum:EPSG::5171’
  • If value = ‘AHD’, then replace it with ‘urn:ogc:def:datum:EPSG::5111’
  • If value = ‘NAVD88’, then replace it with ‘urn:ogc:def:datum:EPSG::5103’
  • If another value represented as ‘OTHER:’ is used, then replace it with the text that follows “OTHER:”.

Mapping AIXM 5.2 to AIXM 5.1.1 (backward)

[MAPC-01]

The following algorithm shall be applied:

• For each AirportHeliport, ElevatedCurve, ElevatedPoint, ElevatedSurface.verticalDatum
  • If value = ‘urn:ogc:def:crs:EPSG::5171’, then replace it with ‘EGM_96’
  • If value = ‘urn:ogc:def:crs:EPSG::5111’, then replace it with ‘AHD’
  • If value = ‘urn:ogc:def:crs:EPSG::5103’, then replace it with ‘NAVD88
  • If other value is used, then replace it with ‘OTHER:<new value of verticalDatum>’

Mapping example

(Note: for mapping test data see: https://github.com/aixm/mapping_52_511/tree/master/AIXM-xxx) 

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