| Frey O, Werner C and Caduff R (2024), "Simultaneous Car-Borne SAR Imaging at L-Band and Ku-Band for DInSAR-Based Mobile Mapping of Ground Motion in Alpine Terrain", In Proc. of EUSAR 2024 - 15th European Conference on Synthetic Aperture Radar. Munich, Germany, April, 2024. , pp. 1259-1264.
[Abstract] [BibTeX] [URL]
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| Abstract: In this contribution, we present high-resolution car-borne DInSAR imagery of a fast-moving landslide, simultaneously acquired at Ku-band and L-band. Recently, we have developed and implemented a car-borne and UAV-borne DInSAR end-to-end system at L-band also including INS/GNSS-based navigation, SAR focusing, and interferometric processing. Using this L-band SAR system we have demonstrated car-borne and UAV-borne measurements of ground motion at various sites. We then enhanced the car-based setup by adding a Ku-band SAR system alongside the Gamma L-Band SAR. In October 2023, we revisited the Brinzauls landslide in Switzerland, where we acquired high-resolution car-borne repeat-pass DInSAR data at Ku-band and L-band. This active landslide consists of various compartments with different kinematic behavior and with different land cover. Our car-borne DInSAR imagery obtained at Ku-band and L-band provides critical information at high spatial resolution to localize and distinguish landslide compartments moving at different velocities for a more detailed mapping of geological-kinematic features within the landslide. |
BibTeX:
@inproceedings{freyEtAlEUSAR2024CarborneDInSARBrinzaulsKuAndLBand,
author = {Othmar Frey and Charles Werner and Rafael Caduff},
title = {Simultaneous Car-Borne SAR Imaging at L-Band and Ku-Band for DInSAR-Based Mobile Mapping of Ground Motion in Alpine Terrain},
booktitle = {Proc. of EUSAR 2024 - 15th European Conference on Synthetic Aperture Radar},
year = {2024},
pages = {1259-1264},
url = {https://www.gamma-rs.ch/uploads/media/freyEtAlEUSAR2024CarborneDInSARBrinzaulsKuAndLBand.pdf}
}
|
| Deeb EJ, Meehan TG, O'Neel S, Keskinen Z, Werner C, Forster R, Frey O and LeWinter A (2023), "Investigations of ground-based mobile L-band InSAR phase response to the application of soil moisture on a high-desert grassland", In Proc. IEEE Int. Geosci. Remote Sens. Symp.. Pasadena, July, 2023. , pp. 2691-2692. IEEE.
[Abstract] [BibTeX] [DOI]
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| Abstract: In an agricultural river valley in central Idaho, USA, weconducted a case study to investigate interferometric synthetic aperture (InSAR) coherence and phase response as an indication of soil moisture change. Throughout a 3-day observational campaign, repeated observations were acquired from a mobile vehicle with a multi-polarization L-band (1.6GHz) InSAR system, first prior to controlled irrigation and then during a dry-out period. Here, we present results that show the time series of coherence and phase in coordination with in-situ soil moisture observations at two depths over the three days of the controlled experiment. During the subsequent dry out period, the time series of interferometric coherence shows an immediate degradation of the signal with a subsequent improvement. The in-situ soil moisture observations highlight this transition of controlled irrigation to subsequent drying out of the soils. We anticipate future work to include investigation of the interferometric times series of phase change as it relates to quantitative changes in soil moisture. |
BibTeX:
@inproceedings{deebEtAl2023CarborneLBandSARSoilMoisture,
author = {Deeb, Elias J. and Meehan, Tate G. and O'Neel, Shad and Keskinen, Zachary and Werner, Charles and Forster, Richard and Frey, Othmar and LeWinter, Adam},
title = {Investigations of ground-based mobile L-band InSAR phase response to the application of soil moisture on a high-desert grassland},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {IEEE},
year = {2023},
pages = {2691-2692},
doi = {10.1109/IGARSS52108.2023.10282878}
}
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| Frey O, Werner C and Caduff R (2023), "Car-borne Mobile Mapping of Ground Motion by Means of Repeat-Pass SAR Interferometry: Case Studies and Application Development Based on L-Band and Ku-band SAR Data Acquisitions", In Proc. IEEE Int. Geosci. Remote Sens. Symp.. Pasadena, July, 2023. , pp. 1902-1905. IEEE.
[Abstract] [BibTeX] [DOI] [URL]
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| Abstract: Ground-motion-related geohazards are omnipresent in alpine areas. Time series of spaceborne SAR data are routinely used to assess surface displacement with large coverage. However, there are also many cases and expositions for which terrestrial radar systems are more suitable to obtain measurements of ground motion. Observing a mountain slope from a moving car or a UAV and thereby spanning a much longer synthetic aperture allows using also lower frequencies, such as L-band, with good spatial resolution. In addition, if aperture synthesis using a mobile mapping SAR system is employed at higher frequencies, the azimuth resolution can also be further improved compared to the azimuth resolution of (quasi-) stationary radar system at larger range distances of several kilometers. In this contribution,we report case studies that we are conducting to further develop and consolidate ground motion mapping by means of our carborne DInSAR system as an operational application. |
BibTeX:
@inproceedings{freyEtAlIGARSS2023CarborneLandKuBandDInSARForGroundMotion,
author = {Frey, Othmar and Werner, Charles and Caduff, Rafael},
title = {Car-borne Mobile Mapping of Ground Motion by Means of Repeat-Pass SAR Interferometry: Case Studies and Application Development Based on L-Band and Ku-band SAR Data Acquisitions},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {IEEE},
year = {2023},
pages = {1902-1905},
url = {https://www.gamma-rs.ch/uploads/media/freyEtAlIGARSS2023CarborneLandKuBandDInSARForGroundMotion.pdf},
doi = {10.1109/IGARSS52108.2023.10283211}
}
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| Frey O, Werner C and Caduff R (2023), "Concurrent Car-Borne Repeat-Pass SAR Interferometry at L-Band and Ku-Band For Mobile Mapping of Ground Motion on Alpine Valley Slopes", In ESA FRINGE 2023. Leeds, UK, September, 2023. ESA.
[BibTeX] [URL]
|
BibTeX:
@inproceedings{freyEtAlFRINGE2023,
author = {Othmar Frey and Charles Werner and Rafael Caduff},
title = {Concurrent Car-Borne Repeat-Pass SAR Interferometry at L-Band and Ku-Band For Mobile Mapping of Ground Motion on Alpine Valley Slopes},
booktitle = {ESA FRINGE 2023},
publisher = {ESA},
year = {2023},
url = {https://www.youtube.com/watch?v=uDMxIs-CIJI}
}
|
| Frey O, Werner C and Caduff R (2022), "Dual-frequency car-borne DInSAR at L-band and Ku-band for mobile mapping of surface displacements", In Proc. of EUSAR 2022 - 14th European Conference on Synthetic Aperture Radar., July, 2022. , pp. 489-492. VDE Verlag GmbH.
[Abstract] [BibTeX] [URL]
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| Abstract: We present our recent developments and experimental results on car-borne mobile mapping of ground-surface displacementswith our in-house-developed SAR systems. Recently, we have successfully demonstrated car-borne andUAV-borne DInSAR with the Gamma L-band SAR system. Meanwhile we have upgraded our car-borne measurementconfiguration that now permits acquiring simultaneously at L-band and at Ku-band. We show first interferometricresults with short temporal baselines from simultaneous acquisitions at both frequencies and in particular we discussthe complementary aspects of the two frequencies in terms of sensitivity to line-of-sight displacements and temporaldecorrelation in typical measurement scenarios. |
BibTeX:
@inproceedings{freyWernerCaduffEUSAR2022DualFrequencyCarborneDInSARatLBandAndKuBandForMobileMappingOfSurfaceDisplacements,
author = {Frey, Othmar and Werner, Charles and Caduff, Rafael},
title = {Dual-frequency car-borne DInSAR at L-band and Ku-band for mobile mapping of surface displacements},
booktitle = {Proc. of EUSAR 2022 - 14th European Conference on Synthetic Aperture Radar},
publisher = {VDE Verlag GmbH},
year = {2022},
pages = {489-492},
url = {https://www.gamma-rs.ch/uploads/media/freyWernerCaduffEUSAR2022DualFrequencyCarborneDInSARatLBandAndKuBandForMobileMappingOfSurfaceDisplacements.pdf}
}
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| Frey O and Werner CL (2021), "UAV-borne repeat-pass SAR interferometry and SAR tomography with a compact L-band SAR system", In Proc. Europ. Conf. Synthetic Aperture Radar, EUSAR., March, 2021. , pp. 181-184. VDE.
[Abstract] [BibTeX] [URL]
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| Abstract: In this contribution, we present SAR image focusing, interferometric, and first tomographic processing results computed from repeat-pass SAR data sets acquired on-board of a vertical-take-off-and-landing (VTOL) unmanned aerial vehicle (UAV): the data was acquired using a novel compact FMCW L-band SAR system in two repeat-pass SAR campaigns flown on 2019-02-13 and 2019-03-28, respectively. In these demonstration campaigns, the Gamma L-band SAR system was deployed and operated on Aeroscout's VTOL UAV Scout B1-100. Repeat-pass interferograms and coherence maps with a temporal baseline of up to 43 days are presented and a tomographic profile obtained from short-term repeat-pass measurements is shown. The results demonstrate the feasibility of UAV-borne repeat-pass SAR interferometry and SAR tomography at L-band |
BibTeX:
@inproceedings{freyWernerEUSAR2021UAVborneRepeatPassSARInterferometryAndSARTomography,
author = {Frey,Othmar and Werner, Charles L.},
title = {UAV-borne repeat-pass SAR interferometry and SAR tomography with a compact L-band SAR system},
booktitle = {Proc. Europ. Conf. Synthetic Aperture Radar, EUSAR},
publisher = {VDE},
year = {2021},
pages = {181-184},
url = {https://www.gamma-rs.ch/uploads/media/freyWernerEUSAR2021UAVborneRepeatPassSARInterferometryAndSARTomography.pdf}
}
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| Frey O, Werner CL, Manconi A and Coscione R (2021), "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.. , pp. 628-631. IEEE.
[Abstract] [BibTeX] [DOI] [URL]
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| Abstract: In this paper, we present examples of DInSAR-based measurement of surface displacements using a novel compact L-band SAR system that can be mounted on mobile mapping platforms such as a UAV or a car. The good DInSAR system performance is demonstrated and, particularly, we also show a use case in which a car-borne system setup is employed to map surface displacements of a fast-moving landslide and the surrounding area in Switzerland. Our results show that car-borne and UAV-borne interferometric displacement measurements at L-band are feasible with high quality over various natural terrain. This novel compact DInSAR system for agile platforms complements existing terrestrial, airborne, and space-borne radar interferometry systems in terms of its new combination of (1) radar wavelength (sensitivity to displacement/decorrelation properties), (2) spatial resolution, (3) (near-) terrestrial observation geometry, and (4) mobile mapping capability. |
BibTeX:
@inproceedings{freyEtAlIGARSS2021UAVandCarborneDinSARwithGammaLbandSAR,
author = {Frey, Othmar and Werner, Charles L. and Manconi, Andrea and Coscione, Roberto},
title = {Measurement of surface displacements with a UAV-borne/car-borne L-band DInSAR system: system performance and use cases},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {IEEE},
year = {2021},
pages = {628-631},
url = {https://www.gamma-rs.ch/uploads/media/freyEtAlIGARSS2021UAVandCarborneDinSARwithGammaLbandSAR.pdf},
doi = {10.1109/IGARSS47720.2021.9553573}
}
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| Frey O, Werner C and Coscione R (2019), "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.. , pp. 274-277. Institute of Electrical and Electronics Engineers.
[Abstract] [BibTeX] [DOI] [URL]
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| Abstract: In this paper, we present first results of car-borne and UAV-borne mobile mapping of potential surface displacements with a compact repeat-pass interferometric FMCW SAR system at L-band: (1) glacier-flow-induced displacements were measured at Stein glacier in the Swiss alps in car-borne mode along a slightly curved road section; (2) a valley slope was observed repeatedly using the vertical-take-off-and-landing (VTOL) UAV Scout B1-100 flown by Aeroscout. The SAR raw data were focused directly to an image grid in map coordinates, involving a digital elevation model and accurate GNSS/INS navigation data, by using a time-domain back-projection (TDBP) approach. These geocoded complex SAR images then allow to directly form differential interferograms in map coordinates. The feasibility of repeat-pass interferometry using our novel FMCW L-band SAR on mobile platforms such as a car or a UAV is successfully demonstrated with several data examples. |
BibTeX:
@conference{Frey2019274,
author = {Frey, O. and Werner, C.L. and Coscione, R.},
title = {Car-borne and UAV-borne mobile mapping of surface displacements with a compact repeat-pass interferometric SAR system at L-band},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {Institute of Electrical and Electronics Engineers},
year = {2019},
pages = {274-277},
url = {https://www.gamma-rs.ch/uploads/media/freyWernerCoscioneIGARSS2019CARandUAVborneDInSARLBand.pdf},
doi = {10.1109/IGARSS.2019.8897827}
}
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| Frey O, Werner C, Hajnsek I and Coscione R (2018), "A car-borne SAR system for interferometric measurements: Development status and system enhancements", In Proc. IEEE Int. Geosci. Remote Sens. Symp.., July, 2018. , pp. 6508-6511. Institute of Electrical and Electronics Engineers.
[Abstract] [BibTeX] [DOI] [URL]
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| Abstract: Terrestrial radar systems are used operationally for area-wide measurement and monitoring of surface displacements on steep slopes, as prevalent in mountainous areas or also in open pit mines. One limitation of these terrestrial systems is the decreasing cross-range resolution with increasing distance of observation due to the limited antenna size of the real aperture radar or the limited synthetic aperture of the quasi-stationary SAR systems. Recently, we have conducted a first experiment using a car-borne SAR system at Ku-band, demonstrating the time-domain back-projection (TDBP) focusing capability for the FMCW case and single-pass interferometric capability of our experimental Ku-band car-borne SAR system. The cross-range spatial resolution provided by such a car-based SAR system is potentially independent from the distance of observation, given that an adequate sensor trajectory can be built. In this paper, we give (1) an overview of the updated system hardware (radar setup and high-precision combined INS/GNSS positioning and attitude determination), and (2) present SAR imagery obtained with the updated prototype Ku-band car-borne SAR system. 2018 IEEE |
BibTeX:
@conference{Frey20186508,
author = {Frey, O. and Werner, C.L. and Hajnsek, I. and Coscione, R.},
title = {A car-borne SAR system for interferometric measurements: Development status and system enhancements},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {Institute of Electrical and Electronics Engineers},
year = {2018},
pages = {6508-6511},
url = {https://www.gamma-rs.ch/uploads/media/freyWernerHajnsekCoscioneIGARSS2018CarborneSARforInSARDevelopmentAndEnhancements.pdf},
doi = {10.1109/IGARSS.2018.8518840}
}
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| Frey O, Werner C and Wegmüller U (2014), "GPU-based parallelized time-domain back-projection processing for Agile SAR platforms", In Proc. IEEE Int. Geosci. Remote Sens. Symp.. , pp. 1132-1135. Institute of Electrical and Electronics Engineers.
[Abstract] [BibTeX] [DOI] [URL]
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| Abstract: Agile SAR platforms such as an automobile require a flexible SAR processing scheme to account for nonlinear sensor trajectories during the synthetic aperture. In this contribution, a parallelized implementation of a time-domain back-projection SAR focusing algorithm based on NVIDIA's CUDA GPU computing framework is presented and discussed using a car-borne SAR data set. The processing performance is assessed using different hardware. In addition, a pre-processing scheme is described that allows for full 3-D motion compensation, yet staying conveniently in conventional slant-range/azimuth geometry of single-look complex SAR images. 2014 IEEE. |
BibTeX:
@conference{Frey20141132,
author = {Frey, O. and Werner, C.L. and Wegmüller, U.},
title = {GPU-based parallelized time-domain back-projection processing for Agile SAR platforms},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {Institute of Electrical and Electronics Engineers},
year = {2014},
pages = {1132-1135},
url = {https://www.gamma-rs.ch/uploads/media/freyWernerWegmullerIGARSS2014GPUbasedTDBP.pdf},
doi = {10.1109/IGARSS.2014.6946629}
}
|
| Frey O, Werner C, Wegmüller U, Wiesmann A, Henke D and Magnard C (2013), "A car-borne SAR and InSAR experiment", In Proc. IEEE Int. Geosci. Remote Sens. Symp.. , pp. 93-96. IEEE.
[Abstract] [BibTeX] [DOI] [URL]
|
| Abstract: In this contribution, a car-borne SAR and InSAR experiment is described. The slope of a valley was imaged by means of a single-pass InSAR system mounted on a car driving on roads along the bottom of the valley. The GAMMA portable radar interferometer GPRI-II hardware with a modified antenna configuration was used for data acquisition. The experimental setup (1), SAR imagery focused along a slightly curved sensor trajectory (2), and first interferometric results (3) obtained using this configuration are presented. 2013 IEEE. |
BibTeX:
@conference{Frey201393,
author = {Frey, O. and Werner, C.L. and Wegmüller, U. and Wiesmann, A. and Henke, D. and Magnard, C.},
title = {A car-borne SAR and InSAR experiment},
booktitle = {Proc. IEEE Int. Geosci. Remote Sens. Symp.},
publisher = {IEEE},
year = {2013},
pages = {93-96},
url = {https://www.gamma-rs.ch/uploads/media/freyWernerWegmullerWiesmannHenkeMagnardIGARSS2013CARSAR.pdf},
doi = {10.1109/IGARSS.2013.6721100}
}
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| Frey O, Magnard C, Ruegg M and Meier E (2009), "Focusing of airborne synthetic aperture radar data from highly nonlinear flight tracks", IEEE Transactions on Geoscience and Remote Sensing. Vol. 47(6), pp. 1844-1858. IEEE.
[Abstract] [BibTeX] [DOI] [URL]
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| Abstract: Standard focusing of data from synthetic aperture radar (SAR) assumes a straight recording track of the sensor platform. Small nonli neari ties of airborne platform tracks are corrected for during a motion-compensation step while maintaining the assumption of a linear flight path. This paper describes the processing of SAR data acquired from nonlinear tracks, typical of sensors mounted on small aircraft or drones flying at low altitude. Such aircraft do not fly along straight tracks, but the trajectory depends on topography, influences of weather and wind, or the shape of areas of interest such as rivers or traffic routes. Two potential approaches for processing SAR data from such highly nonlinear flight tracks are proposed, namely, a patchwise frequency-domain processing and mosaicking technique and a time-domain back-projection-based technique. Both are evaluated with the help of experimental data featuring tracks with altitude changes, a double bend, a 90° curve, and a linear flight track. In order to assess the quality of the focused data, close-ups of amplitude images are compared, impulse response functions of a point target are analyzed, and the coherence is evaluated. The experimental data were acquired by the German Aerospace Center's E-SAR L-band system. 2008 IEEE. |
BibTeX:
@article{Frey20091844,
author = {Frey, O. and Magnard, C. and Ruegg, M. and Meier, E.},
title = {Focusing of airborne synthetic aperture radar data from highly nonlinear flight tracks},
journal = {IEEE Transactions on Geoscience and Remote Sensing},
publisher = {IEEE},
year = {2009},
volume = {47},
number = {6},
pages = {1844-1858},
url = {https://www.gamma-rs.ch/uploads/media/freyMagnardRueeggMeierTGRS2009Tracks.pdf},
doi = {10.1109/TGRS.2008.2007591}
}
|
| Frey O, Meier EH and Nüesch DR (2005), "Processing SAR data of rugged terrain by time-domain back-projection", In Proceedings of SPIE - The International Society for Optical Engineering. Vol. 5980
[Abstract] [BibTeX] [DOI] [URL]
|
| Abstract: Processing of SAR imagos of rugged terrain deserves special care because the topography affects the focused image in a number of ways. In order to obtain geometrically and radiometrically corrected SAR, images of mountainous areas additional knowledge about the topography and the sensor's trajectory and attitude has to be included in the processing or post-processing steps. Various well-known focusing techniques are available to transform SAR, raw data into a single look complex image such as the range-Doppler. the chirp scaling or the Ï-k algorithm. While these algorithms perform the azimuth focusing step in the frequency domain the time-domain back-projection processing technique focuses the data geometrically, i.e., in the time domain. In contrast to the frequency-domain techniques, time-domain back-projection maintains the entire geometric relationship between the sensor and the illuminated area. This implies a couple of advantages: a stringent, terrain-based correction for the elevation antenna gain pattern may be implemented and topography-induced variation of radar brightness can be eliminated in a single step. Further, the SAR image is focused directly onto an arbitrary reconstruction grid and in the desired geodetic reference frame without requiring any additional processing steps. We discuss the influence of rugged terrain on the radiometric properties of focused SAR, data and demonstrate how the time-domain bock-projection approach accounts for these effects within one integrated processing frame-work by incorporating both a correction for terrain slope induced variation of radar brightness and a stringent correction for the elevation antenna gain pattern. The algorithm is evaluated for ENVISAT/ASAR, image mode data of a mountainous area. |
BibTeX:
@conference{Frey2005a,
author = {Frey, Othmar and Meier, Erich H. and Nüesch, Daniel R.},
editor = {Posa F.},
title = {Processing SAR data of rugged terrain by time-domain back-projection},
booktitle = {Proceedings of SPIE - The International Society for Optical Engineering},
year = {2005},
volume = {5980},
url = {https://www.gamma-rs.ch/uploads/media/FreyMeierNueesch_SPIE2005.pdf},
doi = {10.1117/12.627647}
}
|