ICAO Annex 3 states that the upper limit of prevailing horizontal visibility shall be reported as greater than 10 kilometers (6 statute miles). If an observer reports aerodrome visibility of 25 statute miles, this is indicated in the IWXXM message as "greater than 10 km". Thus, the actual visibility values greater than this upper limit are lost in IWXXM messages. To report such cases of unrestricted visibility in IWXXM messages, a new XML type would be needed for <iwxxm:AerodromeHorizonalVisibility>'s extension element.
ICAO Annex 3 states that the upper limit of prevailing horizontal visibility shall be reported as greater than 10 kilometers (6 statute miles). If an observer reports aerodrome visibility of 25 statute miles, this is indicated in the IWXXM message as "greater than 10 km". Thus, the actual visibility values greater than this upper limit are lost in IWXXM messages. To report such cases of unrestricted visibility in IWXXM messages, a new XML type would be needed for
<iwxxm:AerodromeHorizonalVisibility>'s extension element.