Quay walls in Amsterdam’s historic city center
The City of Amsterdam is facing the huge task of assessing and potentially replacing 200 km of the quay walls along its charming old inner-city canals. Adjacent historical buildings are often susceptible to damage by nearby construction activities. Satellite InSAR is being used to monitor areas across the city. Monitoring displacement is seen as a vital tool in the efforts to preserve the physical charm and historical assets of this scenery.
Deltares, the City of Amsterdam, TU Delft, and SkyGeo have published an article on the reliability of PS-INSAR usage compared to regular ground levelling and general InSAR data. It describes how the PS-InSAR process can considerably reduce the current lengthy period required for levelling updates and verifies the improvement in reliability when using a locally optimized SkyGeo InSAR dataset.
The City of Amsterdam started innovating by using levelling techniques centuries ago, when they introduced the NAP (National Reference Height). They have been measuring and placing markers on buildings throughout the city to aid in the assessment of displacement. This is a profound effort as the inner-city is completely built on soft soil. Levelling and InSAR data usage are both used across the city to provide valuable insights on displacement. A direct comparison between levelling and satellite measurements means little, but researchers found a specific statistical procedure that is applied to levelling and satellite measurements to verify their reliability and determine the rate of vertical displacement of the buildings.
Permanent Scatterer SAR
The Permanent Scatterer SAR technique can measure deformations of objects with high reliability. Satellites launched in the last decade produce raw data to obtain displacement time series with high temporal and spatial resolution. Martijn Houtepen, InSAR Applications Expert at SkyGeo, was asked to supply two different datasets for the Amsterdam city area. One general dataset covering the entire city and a tailor-made locally optimized InSAR dataset. Three case studies were reviewed. The results exhibited a near 100% coverage for buildings in the SkyGeo locally optimized dataset. These structures all had reliable measurement points, greatly outnumbering general InSAR and regular levelling results.
Conclusion of the PS -InSAR study
The results of this study support how SkyGeo engages and advises customers. There is merit in the insight building fine-tuning of local datasets. Caution should be considered with generic, publicly available, InSAR datasets. All three case studies showed displacement rates of the satellite measurements are significantly higher than those of the levelling on the same buildings. Locally optimized PS-InSAR satellite measurements are most suitable for assessing the displacement rate of buildings in the Amsterdam inner-city. PS-InSAR is available for SkyGeo customers looking to scale trust with InSAR data.