The unit of measure that applies to altitude.

Example value
MTR
Code lists
Recommendation 20, including Recommendation 21 codes - prefixed with X (UN/ECE)
Rules
Identifier/Error message Flag
PEPPOL-T123-B16102
Value MUST be part of code list 'Recommendation 20, including Recommendation 21 codes - prefixed with X (UN/ECE)'.
fatal