Abstract
This work presents an overview of the multiple aperture synthetic aperture radar interferometric (MAI) technique, which is primarily used to measure the along-track components of the Earth’s surface deformation, by investigating its capabilities and potential applications. Such a method is widely used to monitor the time evolution of ground surface changes in areas with large deformations (e.g., due to glaciers movements or seismic episodes), permitting one to discriminate the three-dimensional (up–down, east–west, north–south) components of the Earth’s surface displacements. The MAI technique relies on the spectral diversity (SD) method, which consists of splitting the azimuth (range) Synthetic Aperture RADAR (SAR) signal spectrum into separate sub-bands to get an estimate of the surface displacement along the azimuth (sensor line-of-sight (LOS)) direction. Moreover, the SD techniques are also used to correct the atmospheric phase screen (APS) artefacts (e.g., the ionospheric and water vapor phase distortion effects) that corrupt surface displacement time-series obtained by currently available multi-temporal InSAR (MT-InSAR) tools. More recently, the SD methods have also been exploited for the fine co-registration of SAR data acquired with the Terrain Observation with Progressive Scans (TOPS) mode. This work is primarily devoted to illustrating the underlying rationale and effectiveness of the MAI and SD techniques as well as their applications. In addition, we present an innovative method to combine complementary information of the ground deformation collected from multi-orbit/multi-track satellite observations. In particular, the presented technique complements the recently developed Minimum Acceleration combination (MinA) method with MAI-driven azimuthal ground deformation measurements to obtain the time-series of the 3-D components of the deformation in areas affected by large deformation episodes. Experimental results encompass several case studies. The validity and relevance of the presented approaches are clearly demonstrated in the context of geospatial analyses.
Highlights
The exploitation of Earth observation (EO) methods, based on the use of instruments operating in the microwave region of the electromagnetic spectrum, represents a common practice nowadays in the scientific community [1,2,3,4,5,6]
Such a problem has been overcome in recent years through the application of pixel-offset (PO) tracking [40] and multiple aperture synthetic aperture radar (SAR) interferometry (MAI) [41] approaches, which both permit computing the dynamics of large along-track ground surface changes
The Minimum Acceleration combination (MinA) combination technique was applied to the two sets of geocoded data, to decompose the LOS-projected deformation measurements along the east–west and up–down directions, as shown in Figure 25A,B, respectively
Summary
The exploitation of Earth observation (EO) methods, based on the use of instruments operating in the microwave region of the electromagnetic spectrum, represents a common practice nowadays in the scientific community [1,2,3,4,5,6]. PO methods initially were mostly applied to studying single deformation events [32,40,42,43,44,45,46], but recently some efforts have been made to extend these techniques to investigating SAR Doppler anomalies in focused SAR data [47] and for the generation of 3-D ground displacement time-series [48] The latter is obtained by combining the information derived from both sequences of multi-temporal DInSAR interferograms and amplitude maps (e.g., [48]). We have adequately adapted the technique initially proposed in [75] to overcome the challenge of combing along-track MAI-driven measurements By applying both the proposed method and original MinA technique, we have retrieved the north–south and the two-dimensional (up–down, east–west) ground displacement time-series of the investigated areas, recovering the (whole) 3-D dynamics of the observed deformation phenomena.
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