Interferometric Synthetic Aperture Radar
The deployment of InSAR as a monitoring tool was crucial to understanding the potential land deformation threats on the M11. Here, InSAR provided detection of subtle ground movements over large areas along roads and embankments where traditional inspections occur infrequently – sometimes every 10 years. 8 It also helped identify previously unknown movement trends, such as seasonal shrink-swell behaviour in clay soils and slow progressive slope instabilities. For example, at the Woodcliffe cutting on the A56, where PSInSAR detected a landslip zone caused from cyclical shrink-swell motions of London clay. The article concluded that InSAR was found to be a hugely successful monitoring tool that uncovered a plethora of unforeseen problems, that otherwise would have been inspected at the mentioned once per decade frequency. It also appraises the range of detail in InSAR performance, both by providing ‘greater spatial coverage’ across the entirety of the UK, and its ability to be compatible with other forms of monitoring, justifying that ‘small-scale features (e.g. defective drainage) that could result in asset performance issues may be missed by remote sensing alone’. 9 The crucial point from this particular case is that InSAR is not to be used as an individual monitoring method in any case, let alone in a more complicated and unpredictable urban setting. Technology penetration Lastly, it is imperative to mention the technology penetration prospects for InSAR. Firstly, the estimated global market size of InSAR in 2024 was $180 million. 10 With a market expectation to triple by 2031, at a 16% Compound annual growth rate, it is clear from an analytical perspective that InSAR usage and implementation is growing at a rapid pace. The acceleration is driven by advancements in satellite availability and accessibility, as well as a regularly improving cost-effectiveness analysis. Furthermore, the progression of technology in the technical perspective has also advanced beyond all other forms of monitoring. For example, the data accuracy of InSAR – at +-2mm - is much more precise
8 Pritchard 2023 (n.6). 9 Ibid. 10 Internal statistics from my internship with GeoKinesia, based on private images from EUSPA and Euroconsult conferences.
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