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  • Maria C. Blanco.

InSAR: Satellite images for detecting and measuring ground deformation.

Remote sensing techniques have been developed since the launch of the first Earth observation satellite in 1972. Although initially underutilized due to the high cost of accessing the data, nowadays the systematic use of satellite images is increasingly applied in projects of different disciplines.

By using electromagnetic radiation as a source of energy, remote sensors capture a series of data that are processed to obtain information about the Earth's surface. Reflected sunlight is one of the types of radiation commonly measured by sensors.

There is another type of sensor capable of controlling the frequency of the wave of the signal they emit since they generate their own source of energy. The Synthetic Aperture Radar (SAR) system is an active sensor that sends electromagnetic pulses to the Earth in order to register their return once it is reflected by the surface.

One of the most important characteristics of SAR is that it operates both day and night. On the other hand, the signals used by these radars work in the electromagnetic spectrum band of microwaves. This characteristic gives it a series of very important advantages such as the ability to penetrate clouds and other atmospheric phenomena such as rain.

What is InSAR?

Synthetic Aperture Radar Interferometry (InSAR) detects and measures displacement over time. This technology is based on the comparison of multiple pairs of radar images. The first step is the generation of interferograms, where the phase interference pattern of the waves of two images of the same surface is compared, pixel by pixel. This difference represents the magnitude of displacement between the images acquired on different dates. Subsequently, processing techniques are applied to remove noise and improve the quality of the measurements. Finally, the displacement is visually represented on optical images to easily interpret which areas are or have been deforming over the study time.

This technology allows the detection and measurement of ground and infrastructure displacement in extensive areas which serves to help prevent environmental accidents, improve safety and maintain operational success.

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