I have written previously about the studies EARSC has been undertaking into the economic benefits arising from the use of satellite imagery. Our approach is completely bottom-up. We analyse the impact that a single product has on a complete value-chain, from the primary service provider through to the citizens. The first two cases we looked at were: the use of radar imagery to support winter shipping, navigating through ice in the Baltic (January 2016), and how clear-cut maps derived from satellite optical imagery allows forest owners to improve the quality of their timber stocks in Sweden (May 2016).
In my third column, I’d like to examine the impact of the use of satellite radar imagery to monitor gas and water pipeline infrastructure in The Netherlands. Ground subsidence is a particular problem in the area around Rotterdam as well as in other parts of the country. It can be so severe that soil levels can change by as much as 1m within a few years. This causes problems for underground pipelines making up the infrastructure of the area to deliver gas, water and steam to local citizens and businesses. The problem is most acute where pipelines connect to the consumers’ houses or where they cross over one another under the roads. The ground sinks, taking the pipeline with it, whilst the house, being deeply anchored does not move. In each case, a fracture risks a severe accident or disruption to local citizens.
How to know where the risk lies? Older connections are more at risk than modern ones as they are made of rigid metal rather than flexible plastic and the current practice is to install a loop to absorb movement. Clearly the risk is greater where the ground is subsiding faster. In this case, the stress created on the household gas connection or on the water mains in the street can cause a failure with consequent leaks. In the case of water, this can cause severe disruption to traffic or, as in one case, the flooding of a hospital basement; in the case of gas, the impact can be much worse if gas builds up in the space under a house when it may even explode.
Companies operating the pipeline infrastructure for the delivery of gas and water, such as Stedin (Rotterdam) and Oasen (Gouda), have had planned replacement programmes that start in areas where leaks have been previously reported and are found to be due to subsidence. This leads to some of the pipes and connections being replaced prematurely – that is, when there is no immediate need to do so.
A more targeted approach is possible using satellite images. SkyGeo – a Dutch EO service provider – supplies maps that show hot spots where ground movement is taking place (see Figure 1). Imagery from satellite-borne Synthetic Aperture Radar (SAR) from the Sentinel-1 mission (part of the Copernicus programme) is used to show where and by how much the ground is subsiding and TerraSAR-X (a commercial mission) is used to further pinpoint the movement more precisely. Ground deformation can be measured quite precisely using SAR imagery from sequential passes over the site being monitored.
The combination has allowed Stedin and Oasen to develop a new maintenance strategy that is based on connections of higher risk. Instead of replacing pipes and connections in a single district, no matter the age or the actual risk of failure, a much more focused approach becomes possible where pipes at risk, serving individual houses or streets, can be replaced.
The result is a much better use of resources by the pipeline operators, as operational and investment costs drop significantly, and less risk to consumers from gas leaks or disruption from major water leaks. Overall, we calculate an economic benefit coming from the use of this product by the two named infrastructure operators in the Netherlands to be €6.6m-€7.9m per annum. Extrapolated to the other operators across the whole country; factoring in the subsidence risk for each area, leads us to conclude that there is a total potential benefit to the Netherlands of €15.2m-€18.3m each year.
This result is shown in Figure 2 as cumulative benefits along the value-chain in which Tier 1 is the EO Service Provider (SkyGeo), Tier 2 is the pipeline operators (Stedin and Oasen), Tier 3 is the local authorities (not available to consult with), and Tier 4 is the citizens and the local economy.
Geoff Sawyer is EARSC secretary general (www.earsc.org)