An InSAR based planning tool for maintaining the Dutch height system

The Dutch height system, called Normaal Amsterdams Peil (NAP), is realized purely trough leveling between designated benchmarks. In a cycle of 10 years secondary NAP benchmarks, generally located in buildings and civil engineering structures, are surveyed to provide actual and reliable heights. However, leveling campaigns are very labor-intensive and take a lot a of time, resulting in high costs. Furthermore, the planning of secondary leveling is based on limited prior knowledge. Instead of yearly leveling of each bench mark within a region, the strategy could be optimized such that deforming areas are visited more often and stable areas less. Trends estimated from historical NAP data could be used, but these provide insufficient information about stability and reliability of published heights. Therefore we propose to use a nationwide deformation map derived from InSAR satellite data to optimize the planning of the secondary leveling campaigns. By using InSAR deformations combined with information of the NAP benchmarks such as measurement date, type and location, a planning tool has been developed. The first targeted leveling of NAP benchmarks using this tool is planned for 2020.