The AOD (NAP) and its uses
The Amsterdam Ordnance Datum (AOD) known as Normal Amsterdam Level (NAP) is a horizontal plane (corresponding approximately with average sea level) with respect to which we indicate the height of land and water in the Netherlands. For example after a level measurement of a dyke or a road you can say “this dyke is 3,24 meters above AOD” or “this road is 1,40 meters below AOD.” The land in the west of the Netherlands lies below sea level for the most part. Good water management to prevent waterlogging and floods is of vital importance for the Netherlands and for this management the NAP is indispensable.
Almost the half of the Netherlands lies below AOD