As explained in the data encoding section, 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 values: UomDistanceVerticalType;
- 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 rules shall be applied for the automatic production of the NOTAM text (decoding of the vertical limits):
...
- The values FLOOR and CEILING will not occur in the items F or G, just in the decoding of vertical limits in item E of some particular scenarios;
- The decoding for the values having as reference 'W84' is provided for completeness sake, but they will not occur in the current practice;
- The decoding of "standard meters" (SM) is similar to the decoding of the FL values; although this value is not mentioned in the OPADD, there is no reason to exclude it from this decoding, for those regions that use SM instead of FL.