The Amsterdam Ordnance Datum Dynamic Vertical Reference Frame NAP-D2023P1
What's in it
As of 2026, the vertical reference frame of the Amsterdam Ordnance Datum (NAP) comprises 346 deeply founded first-order benchmarks and more than 80,000 second-order benchmarks. Benchmark elevations are published by [1–3] as static values: the most recently determined elevation remains the officially assigned value until a subsequent leveling survey provides an update. Consequently, the published benchmark elevation time series exhibit stepwise changes rather than continuous temporal variations.All elevations are referenced to a datum defined by one or more benchmarks whose elevations are treated as deterministic and fixed. During the fifth national leveling campaign, it was established that the original reference benchmark in central Amsterdam, dating from the 1930s, had undergone vertical displacement. The NAP reference was therefore transferred to a group of benchmarks in the Veluwe and Utrechtse Heuvelrug regions [2]. Because previously published elevations were not retroactively adjusted to the revised datum, this change introduced additional discontinuities into the historical benchmark elevation records.Although these inconsistencies are generally acceptable for many civil …
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