InSAR innovation on reference height network NAP

The main application is the development of a change-oriented planning tool for maintaining the Dutch height network NAP (Normaal Amsterdams Peil). Furthermore, it leads to the development of a quarterly update national signalling map of changes in infrastructure behaviour. The second outcome of the tender process is Skygeo is now preferred supplier for all InSAR related projects among which high resolution radar analysis.

Rijkswaterstaat is responsible in the Netherlands for the design, construction, management and maintenance of the main road network and water management. This inludes the national waterways network of canals, rivers and navigation channels in open water and the national water system. One of the tasks of Rijkswaterstaat is to carefully map the surface height of the Netherlands. The Netherlands, which is mainly a large delta that is located for a significant part below sea level, is very vulnerable and hence needs to be protected against large water discharge through the rivers and sea level rise. Large water defence systems are built, such as storm barriers, dikes and levees.

Normaal Amsterdams Peil

The Netherlands is confronted by two main threats: Rising water levels and displacement. The land displacement is not only due to mining activities but also due to peat compaction. Mining activities, in the Netherlands mainly gas and salt mining, lead to displacement bowls in mining areas. Land displacement due to peat oxidation is a problem in the western part of the country caused by pumping water and maintaining ground water levels. The combination of increased water levels and subsiding soil, makes accurate height information one of the key safety factors in the Netherlands. Other main types of surface displacement that occur in the Netherlands are uplift above abandoned coal mines and periodic displacement due to gas storage. Furthermore, there is the monitoring of infrastructure, such as the water defence systems, settling and degradation of roads, highways and rail infrastructure.

The Normaal Amsterdams Peil (NAP) is the reference level for heights in the Netherlands. The NAP is a dense network of about 35000 benchmarks, of which about 400 are deeply founded underground benchmarks. On the one hand, the benchmarks form the basis for the geodetic network in the Netherlands, as mentioned above, and on the other hand they form an important basis for the initial height determination and stability monitoring of all civil infrastructure.

The benchmarks are measured using optical levelling. With InSAR every day millions of measurements are made in a single acquisition over areas of the size of the Netherlands. The objective is to make a Nationwide Deformation Map available that provides co-governments (central government and local authorities) with medium-resolution and high time-frequency dynamic height data both in vertical and in east-west direction. InSAR will not replace existing measurements, it will complement existing measurements and serve as a guideline for more efficient use of traditional measurement techniques.

InSAR Context is everything

“Using the SkyGeo contextual approach the area data can be mathematically enhanced to fully approach the real situation. That’s why SkyGeo has vastly expanded it’s  consultancy division in recent months to assist governments and global companies to make better decisions based on InSAR data.” Says Pieter Bas Leezenberg, CEO of SkyGeo.

The Nationwide Deformation Map is a great step forward towards full adoption of InSAR for maintenance and modelling purposes. The map is not visualising raw data but a tailor made dataset specifically made for Rijkswaterstaat for the purpose of the reference height map. We partner strongly to make the Nationwide Deformation Map powerful and consult in making the best possible choices for cut-offs and filters. The Nationwide Deformation Map is not a “one size fits all”- solution. Strict caution is needed in area’s of (great) instablity, because the chosen filters and cut-offs in the Map can significantly influence the outcome of your analysis. If your organisation wants to make decisions based on the Nationwide Deformation Map about displacement, we strongly advise to consult our Geomatic Engineers and attend workshops at the SkyGeo Academy before making any assumptions on outcomes of your analysis.

InSAR going mainstream

More than a decade ago, when SkyGeo was founded by Leezenberg and Professor Ramon Hanssen of the Technical University of Delft, using InSAR data to for earth observation was exciting and new. Scientists discovered new approaches and algorhytms on a monthly basis. SkyGeo was the worlds first independent InSAR consultancy company, dedicated on making applied InSAR usage work in Area and Infrastructure Management. Nowadays, expanding to multiple continents, it is the leading InSAR Only company in the world trusted by the largest corporations and governements. The Open Data policy by Dutch governement has made over 12.000 datasets publicly available, the Nationwide Deformation Map is expected to be available in the future. Going mainstream will mean that vast numbers of users will embrace the new displacement dataset, making analysis based on their findings without deeper knowledge of the datasets used. By forming our InSAR educational platform SkyGeo Academy and introducing consultancy for (local) governements and businesses who want to incorporate the data into their work processes in The Netherlands we’re fully charged to assist in better understanding of InSAR and better usage of the Nationwide Deformation Map.

Bodemdalingskaart.nl or Nationwide Deformation Map

In recent years SkyGeo also succesfully released bodemdalingskaart.nl, a map of the Netherlands that frontpaged every newspaper in 2018 and had a major update in 2019. Key difference between the two maps is that Nationwide Deformation Map is a pointmap where individual measurements and timeseries are visualised as data points. Bodemdalingskaart.nl is an Area Movement map, it is ready made to overview larger areas and uses a 2x2KM grid that contains up to 30 times more data. Another big difference is bodemdalingskaart also distinguises between shallow (peat) and deep (gas-winning) displacement. Both maps are perfect examples of Open Data InSAR usage, where everyone can do basic analysis on high quality InSAR maps.