Terrestrial radar interferometry (TRI) has become an operational tool to measure slope surface displacements [1,2]. The day-and-night and all-weather capability of TRI together with the ability to measure line-of-sight displacements in the range of sub-centimeter to sub-millimeter precision are strong assets that complement other geodetic measurement techniques and devices such as total stations, GNSS, terrestrial laser scanning, and close/mid-range photogrammetric techniques.
(Quasi-)stationary TRI systems are bound to relatively high frequencies (X- to Ku-band or even higher) to obtain reasonable spatial resolution in azimuth and yet the azimuth resolution is typically only in the order of tens of meters for range distances beyond a few kilometers. These aspects are limiting factors to obtain surface displacement maps at high spatial resolution for areas of interest at several kilometers distance and also for (slightly) vegetated slopes due to the fast temporal decorrelation at high frequencies.
Recently, we have implemented and demonstrated car-borne and UAV-borne repeat-pass interferometry-based mobile mapping of surface displacements with an in-house-developed compact L-band FMCW SAR system which we have deployed 1) on a car and 2) on VTOL UAVs (Scout B1-100 and Scout B-330) by Aeroscout GmbH [3,4]. The SAR imaging and interferometric data processing is performed directly in map coordinates using a time-domain back-projection (TDBP) approach [5,6] which precisely takes into account the 3-D acquisition geometry.
We have meanwhile further consolidated our experience with the repeat-pass SAR interferometry data acquisition, SAR imaging, interferometric
processing, and surface displacement mapping using the car-borne and UAV-borne implementations of our InSAR system based on a number of repeat-pass interferometry campaigns. In our contribution, we present the capabilities of this new InSAR-based mobile mapping system and we discuss the lessons learned from our measurement campaigns.
 Caduff, R., Schlunegger, F., Kos, A. & Wiesmann, A. A review of terrestrial radar interferometry for measuring surface change in the geosciences. Earth Surface Processes and Landforms 40, 208–228 (2015).
 Monserrat, O., Crosetto, M. & Luzi, G. A review of ground-based SAR interferometry for deformation measurement. ISPRS Journal of Photogrammetry and Remote Sensing 93, 40–48 (2014).
 O. Frey, C. L. Werner, and R. Coscione, “Car-borne and UAV-borne mobile mapping of surface displacements with a compact repeat-pass interferometric SAR system at L-band,” in Proc. IEEE Int. Geosci. Remote Sens. Symp., 2019, pp. 274–277.
 O. Frey, C. L. Werner, A. Manconi, and R. Coscione, “Measurement of surface displacements with a UAV-borne/car-borne L-band DInSAR system: system performance and use cases,” in Proc. IEEE Int. Geosci. Remote Sens. Symp.IEEE, 2021, pp.628–631.
 O. Frey, C. Magnard, M. Rüegg, and E. Meier, “Focusing of airborne synthetic aperture radar data from highly nonlinear flight tracks,” IEEE Trans. Geosci. Remote Sens., vol. 47, no. 6, pp. 1844–1858, June 2009.
 O. Frey, C. L. Werner, and U. Wegmuller, “GPU-based parallelized time-domain back-projection processing for agile SAR platforms,” in Proc. IEEE Int. Geosci. Remote Sens. Symp., July 2014, pp. 1132–113.