What is Repeat Pass Interferometry?

Remote sensing technologies have revolutionised the field of geoscience, offering profound insights into the Earth’s dynamic processes. Among these technologies, Interferometric Synthetic Aperture Radar (InSAR) stands out, particularly in its application through Repeat Pass Interferometry. This technique has become indispensable for monitoring ground deformation and geohazards with remarkable precision.

The Concept of Repeat Pass Interferometry

Repeat pass interferometry is a technique within the InSAR framework that involves capturing radar images of the same area at different times. This allows for the detection of surface movement by analysing phase differences between the images. The process hinges on the principle that changes in phase caused by surface displacement , can be measured with high accuracy.

How it Works

The method involves acquiring two or more radar images of the same location that a satellite passes at different times. These images are processed to produce an interferogram, which displays phase differences that represent relative ground displacement. Advanced algorithms then convert these differences into precise measurements, enabling detection of even surface changes imperceptible to the naked eye.

Future Prospects

The future of repeat pass interferometry is promising, with ongoing research focused on refining its methodologies and expanding its applications. Emerging technologies, such as compact radar satellites and machine learning algorithms, are poised to further elevate the capabilities of InSAR.

In conclusion, repeat pass interferometry is the cornerstone of modern geoscience, offering unparalleled insights into Earth’s surface dynamics. Its ability to provide precise, long-term monitoring of ground displacement makes it an invaluable tool for understanding and mitigating geohazards. As technology continues to evolve, so will the potential of this remarkable technique.

Application	Optimal Band (Wavelength)	Temporal Resolution	Spatial Resolution	Typical Accuracy
Landslides	C-band (5.6cm)	6-12 days	3-20m	1-3 mm
Urban Subsidence	X-band (3.1cm)	11 days	1-3m	2-5mm
Mining Subsidence	C-band (5.6cm)	6-12 days	3-20m	1-3 mm
Earthquakes	C-band (5.6cm)	Event-based	3-20m	5-15mm
Glacier Movement	L-band (23cm)	12-14 days	3-10m	10-50mm
Coastal Erosion	X-band (3.1cm)	11 days	1-3m	2-5mm
Permafrost Thaw	L-band (23cm)	12-14 days	3-10m	5-10mm
Dam Monitoring	X-band (3.1cm)	11 days	1-3m	1-3mm
Groundwater Pumping	C-band (5.6cm)	6-12 days	3-20m	2-5mm