Core registration normal Amsterdam level (NAP)

The Registration Normal Amsterdam Level (NAP) includes the recorded height measurements of quality marks in Amsterdam. Nationally, the NAP network consists of about 50,000 visible gauge marks and 250 underground gauge marks, of which about 1000 in Amsterdam. A large part of the NAP-level marks are maintained by [Rijkswaterstaat](http://www.rijkswaterstaat.nl), the densification of this network is maintained by the Basic Information Department.