I Amsterdams nye rådhus, kalt for Stopera (sammendragning av stadhuis og opera), som ligger på Waterlooplein langs Amstelelven, er det på muren i hovedpassasjen satt opp en permanent utstilling som viser et snitt av en del av Nederland. Stedet kalles 'NAP-Project'. NAP er referansenivå for høyder i Nederland og de fleste andre land i Europa og vil erstatte Norges 'gamle' referansenivå fra 1954 om ikke så lenge.
I kjelleren er det satt opp et NAP-merket i underetasjen, alt fritt tilgjengelig. Merkets høyde er overført fra merket på Dam-plassen.
N.A.P. = NORMAAL AMSTERDAMS PEIL = AMSTERDAM ORDNANCE DATUM
Amsterdam has received its name from the dam in the river Amstel, which dam served to keep the outer water from flooding the town. To enable ships to enter the town, a lock was built that was closed when the outer water reached a certain height level. This water level seems to be the origin of the Amsterdam ordnance datum. Three centuries ago a standard ordnance datum was established in Amsterdam, based on the average high watermark of the Zuiderzee, which was Amsterdam's connection with the North Sea. This ordnance datum was - and is - the referral point for all constructions of any kind in the Netherlands. It was also adopted for a number of neighbouring countries.
Amsterdam was originally
built on wooden piles. In medieval times these (round) piles rested on an
upper layer of sand. Today concrete (square) piles are being driven into a
more solid lower sand level. The NAP project in the Amsterdam City Hall
was designed and constructed by Louis van Gasteren and Kees van der Veer.
It was officially inaugurated on 18 May 1988.
- The bronze NAP knob, mounted on a concrete pile, represents the exact zero level. You can actually touch it as you go downstairs.
- The three watercolumns represent:
It is interesting to realize as you stand next to the concrete NAP pile, you are actually below sea level! It should be said incidentally that the system is linked by telephone lines with measuring stations located in the North Sea.
- the high or low tide of the North Sea at this particular moment at IJmuiden
- the high or low tide at Flushing (Vlissingen)
- the highest level reached in the disastrous
floods in 1953 in the Province of Zeeland: 4.55 meters above NAP.
- The cross section in natural stone showing the
Netherlands from East to West. We go from the Zuiderzee, which is now
the IJsselmeer, to the North Sea. One gets a good impression of the
countries unique geological structure.
Tverrsnitt av Amsterdam med kanalene, tunnelbane, og bæredyktige sandlag
under byen. Gelenderet er ved trappen ned mot NAP-merket.
- P.I. van der Weele: DE GESCHIEDENIS VAN HET NAP.
RIJKSCOMMISSIE VOOR GEODESIE Delft 1971
- Ir. A. Waalewijn: drie eeuwen normaal amsterdams peil.
hoofddirectie van de waterstaat
's Gravenhage 1987