Minimum Descent Altitude 3 : A specified altitude, referenced to mean sea level, in a non-precision approach or circling approach below which an aircraft descent may not be made without visual reference
Ministry of Business, Innovation and Employment, Glossary of terms and acronyms, Wellington, New Zealand 2010. http://wwwsosh.govt.nz/resources/glossary-u.shtml, (Occupn Hlth and Sfty - Brit) {530}