Amsterdam height

The last of the marble blocks installed in 1683, which remained in place

Amsterdam height (Normaal Amsterdams Peil (NAP)) - a height system used to measure water and land levels in the Netherlands. It refers to the average water level during the summer tides in 1683 in the lake (then IJ Bay) in Amsterdam, the Netherlands.

The Amsterdams Peil (AP, Amsterdam level) was originally designated in the seventeenth century as the point for the water level in the lake (then the IJ Bay) in Amsterdam. In 1683 Mayor of Amsterdam, Johannes Hudde commissioned the marking of eight locks with marble blocks indicating nine feet and five inches (2,676 meters) above the AP (one of these blocks is still in its original place - it is located on the wall of the Eenhoornsluis on the Korte Prinsengracht channel), which meant the level of the embankments at the bay. The horizontal lines on the marble blocks became determinants of the AP height (specifically nine feet and five inches higher than the AP). Analysis of water level measurements from that time shows that the average water level in the IJ during the summer tides in 1683 was considered as AP. Despite the later changes in sea level, the value of AP (later NAP) remained the same. At present, the average North Sea level along the Dutch coast varies (depending on location) between 0 and 10 cm above NAP. In 1683 the AP was 17 cm higher than the average sea level. In the 18th century, especially at the end of the century and at the beginning of the 19th century, the AP spread throughout the Netherlands. In the years 1875-1885 a number of accurate measurements were made, checking the correctness of the nationwide indicators. Incorrect indicators have been improved, many new ones have been installed. Amsterdams Peil was also changed to Normaal Amsterdams Peil (NAP). As a result of this campaign since 1891, NAP is commonly used to denote water and land levels in the Netherlands.

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