Infrastructure owners and operators rely on in-situ instrumentation, such as settlement plates, GNSS stations, piezometers, and inclinometers, to provide precise, trusted measurements at specific locations. These systems form the backbone of many monitoring programmes, offering the “ground truth” essential for understanding structural performance and ensuring safety. Satellite-based Interferometric Synthetic Aperture Radar (InSAR) builds on this foundation. By adding continuous, wide-area measurements from space, InSAR can complement in-situ readings, validate their accuracy, and extend monitoring coverage far beyond instrument locations. The result is a richer, more complete dataset that gives stakeholders both precision at key points and context across the wider site.
How InSAR Works?
InSAR uses radar images captured by satellites on repeat orbits to detect minute changes in the Earth's surface, even up to a few millimetres, by comparing the phase difference of different images taken of the same area at different times.
Because satellites can cover vast areas, InSAR technology enables:
- Wide-area coverage – Monitoring large or remote areas without requiring on-the-ground equipment at every point.
- High-density measurements – Capturing even small targets/objects as data points across the area of interest, thanks to the high resolution of modern radar sensors.
- Frequent visits – Providing updates as often as every 6-12 days on the satellite constellation.
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Why Combine InSAR with In-Situ Sensors?
Individually, each method has strengths:
- In-situ sensors provide ground truth data with extremely high accuracy at specific locations.
- InSAR offers continuous spatial coverage, revealing displacement patterns between and beyond instrument points.
When used together, the benefits include:
1. Validation – Comparing InSAR results with in-situ readings helps confirm measurement accuracy and build confidence in the data.
2. Gap filling – InSAR supplies data between manual collection periods, maintaining a continuous monitoring record.
3. Early detection – Broad coverage allows potential problem areas to be spotted even in places without installed sensors.
4. Cost efficiency – Reduced need for frequent site visits without sacrificing insight.
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Case Study: Tailings Storage Facility in Canada.
A Tailings Storage Facility in Alberta was monitored using settlement plates, GNSS, and LiDAR. While these methods provided valuable readings, data collection intervals left gaps, and full spatial coverage was not possible.
InSAR analysis of the same facility showed a strong correlation with the in-situ measurements. It also revealed deformation trends in unsensed areas and provided a much denser dataset without additional fieldwork. This combination of approaches gave stakeholders a clearer, more reliable picture of ground movement, improved early warning capability, and reduced monitoring costs.
The Takeaway
For asset owners, the integration of InSAR with established in-situ monitoring systems represents a step forward in geotechnical and structural health assessment. It’s not about replacing one method with another, but about leveraging each where it is strongest:
- In-situ instruments deliver point-specific precision.
- InSAR delivers coverage.
Together they provide a more complete, validated, and actionable understanding of ground behaviour – supporting better decision making and safer operations.
FAQs
1. What is InSAR, and how does it work?
InSAR (Interferometric Synthetic Aperture Radar) uses radar images from satellites to detect minute changes in the Earth's surface by comparing images taken at different times. It provides precise measurements of displacement, even at the millimeter level.
2. Why should InSAR be combined with in-situ sensors?
In-situ sensors provide highly accurate data at specific points, while InSAR offers continuous spatial coverage, validating sensor readings, filling data gaps, and helping to detect potential issues even in areas without sensors.
3. What are the advantages of combining InSAR with in-situ monitoring systems?
The combination provides better validation, continuous data collection between manual measurements, early detection of issues in unsensed areas, and cost efficiency by reducing the need for frequent site visits.
4. What type of data does InSAR provide that in-situ sensors cannot?
InSAR provides wide-area coverage and high-density measurements, capturing data from large or remote areas that are difficult or costly to monitor with in-situ sensors.
5. How often can InSAR provide updates?
InSAR can offer updates as frequently as every 6-12 days, depending on the satellite constellation used.
6. What is the role of InSAR in validating in-situ sensor readings?
InSAR compares its results with in-situ measurements to confirm their accuracy and reliability, helping build confidence in the data and ensuring more precise monitoring.
7. How does InSAR help in gap-filling between sensor readings?
InSAR provides continuous monitoring between manual data collection periods, ensuring no gaps in the monitoring record and giving a more consistent understanding of the site's conditions.
8. Can InSAR detect issues in areas without installed sensors?
Yes, InSAR can detect potential problem areas even where in-situ sensors are not installed, enabling early detection of issues that might otherwise go unnoticed.
9. What are the cost benefits of integrating InSAR with traditional monitoring systems?
InSAR reduces the need for frequent site visits and fieldwork, lowering costs while still providing valuable, high-density data for monitoring ground movement and structural performance.
10. What is a real-world example of InSAR being used alongside in-situ sensors?
In a case study of a Tailings Storage Facility in Canada, InSAR was used alongside settlement plates, GNSS, and LiDAR. InSAR showed a strong correlation with the in-situ data and revealed deformation trends in areas that weren’t previously monitored, providing a denser dataset and improving early warning capabilities.