Dr. Davide Oscar Nitti Profile

Dr. Davide Oscar Nitti

Project Manager at GAP Srl

SPIE Involvement:

Author

Publications (23)

Proceedings Article | 13 November 2024 Presentation + Paper

Development of an operational infrastructure monitoring service for predictive maintenance based on Rheticus Safeway

Paolo Petio, Vincenzo Massimi, Daniela Iasillo, Teresa Fazio, Giuseppe Forenza, Nicolò Taggio, Sergio Samarelli, Davide Oscar Nitti, Raffaele Nutricato, Mauro Cardone, Maria Elena Cianfanelli

Proceedings Volume 13197, 131970X (2024) https://doi.org/10.1117/12.3031476

KEYWORDS: Roads, Land cover, Synthetic aperture radar, Satellites, Bridges, Motion measurement, Inspection, Vegetation, Library classification systems, Kinematics

Read Abstract +

Ground motion phenomena can cause serious damage to infrastructures and the environment, and it represents a risk for the citizens. Landslides may destroy roads, and railways, even causing victims. In recent years, the continuous growth of the intensity and frequency of extreme natural phenomena has been observed, and there is a clear relationship between both human activities and climate change.

Planetek Italia, with GAP, is developing an operational infrastructure monitoring service to support predictive maintenance of roads, railways, and bridges. The initiative, supported by the Italian Space Agency (ASI) under the I4DP Market project, targets providing a comprehensive solution aligned with the guidelines for risk classification, safety assessment, and monitoring of existing bridges, as outlined by the Italian Ministry of Infrastructure and Transport.

The proposed operational service builds upon the existing Rheticus Safeway, developed by Planetek within the Horizon 2020 Safeway project concluded in February 2022. The enhancements and adaptations, performed during the ASI project encompass operational and technological aspects, to democratise and scale the service to a European and global level. The service will be based on ground motion data derived from multitemporal satellite interferometry algorithms, primarily leveraging SAR Sentinel-1 (S-1) and COSMO-SkyMed (CSK) data, alongside change detection from multispectral satellite Sentinel-2 (S-2) data.

To ensure the service's generalizability, scalability, and availability across various levels of detail, the European Ground Motion Service (EMGS) of Copernicus is proposed as a baseline service for ground motion monitoring accessible throughout the European Union. An additional service tier with higher temporal and spatial resolution is foreseen to provide updates on-demand, based on SAR COSMO-SkyMed and Sentinel-1 data processing to derive the ground motion map and the Sentinel-2 to identify the land cover changes.

The adoption of this operational infrastructure monitoring service will mark a significant step towards efficient and proactive maintenance strategies, leveraging satellite-based geo-analytics information to ensure the safety and resilience of roads and railways infrastructure networks on a broader scale.

Proceedings Article | 20 October 2023 Presentation

Detection of badland erosion by exploring time series of interferometric coherence and phase

Alberto Refice, Fabio Bovenga, Francesco Lovergine, L. Partipilo, D. Capolongo, Raffaele Nutricato, Davide Nitti

Proceedings Volume PC12732, PC1273201 (2023) https://doi.org/10.1117/12.3007787

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Proceedings Article | 17 October 2023 Presentation + Paper

Exploiting artificial reflectors for SAR interferometry applications

Davide Oscar Nitti, Raffaele Nutricato, Khalid Tijani, Fabio Bovenga, Alberto Refice, Roberto Bellotti, Giovanni Preziosa, Antonio Mongelli

Proceedings Volume 12732, 1273204 (2023) https://doi.org/10.1117/12.2680622

KEYWORDS: Reflectors, Chromium, Synthetic aperture radar, Signal processing, Interferometry, X band, Backscatter, Sensors, Image processing, Transponders

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Proceedings Article | 17 October 2023 Presentation + Paper

Investigating radar cross sections of passive radar reflectors for C-band and X-band SAR satellite missions

Alessandro Parisi, Davide Nitti, Raffaele Nutricato, Giovanni Preziosa, Antonella Loconsole, Francesco Prudenzano, Cataldo Guaragnella

Proceedings Volume 12732, 1273203 (2023) https://doi.org/10.1117/12.2679842

KEYWORDS: Reflectors, Synthetic aperture radar, Radar, Satellites, X band, Radar signal processing, Radar sensor technology, Interferometric synthetic aperture radar

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Proceedings Article | 12 September 2021 Presentation

Identification and analysis of nonlinear trends in InSAR displacement time series

Fabio Bovenga, Alberto Refice, Guido Pasquariello, Raffaele Nutricato, Davide Nitti

Proceedings Volume 11861, 118610G (2021) https://doi.org/10.1117/12.2600135

KEYWORDS: Interferometric synthetic aperture radar, Synthetic aperture radar, Landslides, Kinematics, Statistical modeling, Statistical analysis, Satellites, Nonlinear optics, Interferometry, Interference (communication)

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Multi-temporal SAR interferometry (MTInSAR) allows analysing wide areas, identifying critical ground instabilities, and studying the phenomenon evolution in a long time-scale. Nowadays satellite SAR constellations provide datasets covering time periods of several years with short revisit times, which allow investigating ground displacements showing non-linear kinematics. These are particularly interesting since they include warning signals related to pre-failure of natural and artificial structures. Recently, approaches have been proposed for recognising and analysing nonlinear displacements, which use different strategies. The authors have introduced two innovative indexes for characterising MTInSAR time series: one relies on the fuzzy entropy and measures the disorder in a time series, the other performs a statistical test based on the Fisher distribution for selecting the polynomial model that more reliably approximate the displacement trend. This work reviews the theoretical formulation of these indexes and evaluate their performances by simulating time series with different characteristics in terms of kinematic, level of noise, signal length and temporal sampling. Finally, the proposed procedures are used for analysing displacement time series derived by processing real datasets acquired by both Sentinel-1 and COSMO-SkyMed constellations. In particular the hilly villages of Pomarico and Montescaglioso have been investigated, which are located in Southern Italian Apennine (Basilicata region), in an area where several landslides occurred in the recent past, causing damages to houses, commercial buildings, and infrastructures. The MTInSAR displacement time series have been analysed by using the proposed methods, searching for nonlinear trends that are possibly related to relevant ground instabilities and, in particular, to potential early warning signals for the landslide events affecting Mtescaglioso in 2013 and Pomarico in 2019. Acknowledgments - This work was supported in part by the Italian Ministry of Education, University and Research, D.D. 2261 del 6.9.2018, Programma Operativo Nazionale Ricerca e Innovazione (PON R&I) 2014–2020 under Project OT4CLIMA.

Proceedings Article | 18 October 2019 Presentation

Investigating slope instabilities through SAR interferometry: examples on hilly villages in Southern Italy (Conference Presentation)

Fabio Bovenga, Alberto Refice, Guido Pasquariello, Giuseppe Spilotro, Raffaele Nutricato, Davide Nitti, Maria Chiaradia, Ilenia Argentiero, Roberta Pellicani

Proceedings Volume 11154, 1115403 (2019) https://doi.org/10.1117/12.2533639

KEYWORDS: Synthetic aperture radar, Interferometry, Spatial resolution, Satellites, Interferometric synthetic aperture radar, X band, Data acquisition, Target detection, Space operations, Temporal resolution

Read Abstract +

Multi-temporal SAR interferometry (MTInSAR), by providing both mean displacement maps and displacement time series over coherent objects on the Earth, allows analysing wide areas, identifying critical ground instabilities, and studying the phenomenon evolution in a long time-scale. This technique has been proved to be very useful for detecting and monitoring also slope instabilities. Nowadays, several satellite missions are available providing InSAR data at different wavelengths, spatial resolutions, and revisit time. The high-resolution X-Band COSMO-SkyMed constellation, acquires data with spatial resolution reaching metric values, and provides revisit times of up to a few days, leading to an increase in the density of the measurable targets, thus improving the monitoring of local scale events as well as the detection of non-linear displacements. The recent Sentinel-1 C-band mission from the European Space Agency (ESA), provides a spatial resolution comparable to the previous ESA missions, but a nominal revisit time reduced to 6 days. By offering regular global-scale coverage, better temporal resolution and freely available imagery, Sentinel-1 improves the performance of MTInSAR for ground displacement investigations. In particular, the short revisit time allows a better time series analysis by improving the temporal sampling and the chances to catch pre-failure signals characterised by high rate and non-linear behaviour signals. Moreover, it allows collecting large data stacks in a short time period, thus improving the MTInSAR performance in emergency (post-event) scenarios. These characteristics are very promising for early warning of slope failure events and monitoring subsequent displacements trends. In this work, we present the results obtained by using both COSMO-SkyMed and Sentinel-1 data for investigating the ground stability of hilly villages located in Southern Italian Apennine (Basilicata region). In the area of interest, several landslides occurred in the recent past (e.g. on Montescaglioso in 2013) and also very recently (e.g. on Pomarico in 2019), causing damages to houses, commercial buildings, and infrastructures. SAR datasets acquired by COSMO-SkyMed and Sentinel-1 from both ascending and descending orbits have been processed by using SPINUA MTInSAR algorithm, in order to exploit the potentials of these two satellite missions to investigate ground displacements related to the slope instabilities. Mean velocity maps and displacement time series have been analysed looking, in particular, to non-linear trends that are possibly related to relevant ground instabilities and, thanks to the high spatial resolution, useful in terms of early warning, in the case of rigid soil masses. Results are presented and discussed in relation to the well know events occurred in the area of interest.

Proceedings Article | 11 October 2018 Presentation

Preliminary assessment of side-lobe mitigation techniques for proper coherent targets selection in MTInSAR applications (Conference Presentation)

Paolo Locorotondo, Andrea Guerriero, Maria Teresa Chiaradia, Davide Nitti, Raffaele Nutricato, Fabio Bovenga

Proceedings Volume 10788, 1078804 (2018) https://doi.org/10.1117/12.2325542

KEYWORDS: Synthetic aperture radar, Interferometry, Radar, Backscatter, Picosecond phenomena, Apodization, Target detection, Buildings, Detection and tracking algorithms, Nonlinear filtering

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Multi-temporal Synthetic Aperture Radar Interferometry (MTInSAR) techniques allow detecting and monitoring millimetric displacements occurring on selected targets exhibiting coherent radar backscattering properties. Because of the bandwidth limitation of Synthetic Aperture Radar images, pulse responses are significantly affected by sidelobes that should be identified and masked out before the selection of coherent targets candidates. In fact, sidelobes often exhibit a coherent backscattering behavior and can be hence erroneously identified as persistent scatterers (PS). These artifacts can be also clearly visible in the images, in case of strong scatterers embedded in a surrounding weak clutter environment, such as the echoes generated by ships or buildings. The actual large amount of Geospatial Big Data fosters the implementation of automatic tools for sidelobe detection and cancelation. A number of algorithms have been proposed in the scientific literature for sidelobe reduction in Single-Look-Complex images, ranging from apodization methods to target extraction techniques. In this study we deal in particular with the Spatially Variant Apodization (SVA), a nonlinear filter based on cosine-on-pedestal weighting functions. This approach is attractive because it is able – in theory – to achieve a total sidelobe cancelation, without degrading the original image resolution, and for its computational efficiency. However, as shown in recent works, SVA suffers from several drawbacks: (i) it modifies the statistics of speckle-dominated areas, (ii) a negative bias is introduced in the reflectivity images over homogeneous areas, (iii) the amplitude and phase of the original images could be distorted by the SVA filtering. In particular, it has been demonstrated that SVA filtering compromise the quality of MTInSAR outcomes. Therefore, recent works propose the use of SVA for just identifying and masking out the radar coordinates of the detected side-lobes in the PS candidates position map. In this work we apply SVA for proper coherent target selection in COSMO-SkyMed STRIPMAP co-polarized interferometric data takes, acquired in onshore and offshore environments. In order to highlight both advantages and limitations of this technique, we analyze the performances of SVA approaches in terms of computational efficiency and robustness to focusing artifacts (responsible of non-ideal pulse responses). In particular, we test the SVA filtering both in simulation and in complex real scenarios, where sidelobes of close strong scatterers are mixed and superimposed upon each other. We show the outcomes of MTInSAR techniques before and after the application of SVA filtering. Acknowledgments The research is partly co-funded by the Italian Space Agency in the framework of the FAST4MAP project (“Fast & Advanced SAR Techniques for Monitoring & Alerting Processes” - ASI Contract n. 2015-020-R.0). CSK® Products© of ASI delivered by ASI under a license to use.

Proceedings Article | 3 October 2017 Paper

Investigating ground instabilities in Indonesia through SAR interferometry

Fabio Bovenga, Alberto Refice, Antonella Belmonte, Raffaele Nutricato, Davide Oscar Nitti, Maria Teresa Chiaradia, Sotirios Valkaniotis, Sofia Gkioni, Chrysanthi Kosma, Athanassis Ganas, Paolo Manunta, Elizar, Darusman , Philippe Bally

Proceedings Volume 10426, 1042602 (2017) https://doi.org/10.1117/12.2277838

KEYWORDS: Global Positioning System, Synthetic aperture radar, Interferometry, Satellite navigation systems, Interferometric synthetic aperture radar, Image segmentation, Earthquakes, Motion models

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Proceedings Article | 18 October 2016 Paper

Automatic GCP extraction with high resolution COSMO-SkyMed products

Davide Oscar Nitti, Alberto Morea, Raffaele Nutricato, Maria Teresa Chiaradia, Claudio La Mantia, Luigi Agrimano, Sergio Samarelli

Proceedings Volume 10003, 1000302 (2016) https://doi.org/10.1117/12.2241281

KEYWORDS: Synthetic aperture radar, 3D image processing, Radar, Sensors, Target detection, Corner detection, Silicon, Solid state lighting, Image processing, 3D acquisition

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Proceedings Article | 18 October 2016 Paper

Automatic SAR/optical cross-matching for GCP monograph generation

Raffaele Nutricato, Alberto Morea, Davide Oscar Nitti, Claudio La Mantia, Luigi Agrimano, Sergio Samarelli, Maria Teresa Chiaradia

Proceedings Volume 10003, 1000303 (2016) https://doi.org/10.1117/12.2241284

KEYWORDS: Synthetic aperture radar, Radar, Satellite imaging, Satellites, Error analysis, Image processing, Spatial resolution, Sensors, Image analysis, Image registration

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Proceedings Article | 18 October 2016 Paper

Rheticus: an automatic cloud-based geo-information service platform for territorial monitoring

Sergio Samarelli, Antonio Pio Lorusso, Luigi Agrimano, Raffaele Nutricato, Fabio Bovenga, Davide Oscar Nitti, Maria Teresa Chiaradia

Proceedings Volume 10003, 100030M (2016) https://doi.org/10.1117/12.2241285

KEYWORDS: Synthetic aperture radar, Interferometry, Buildings, Image processing, Radar, Picosecond phenomena, Information technology, 3D image processing, 3D image reconstruction, Image sensors

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Proceedings Article | 15 October 2015 Paper

On the geolocation accuracy of COSMO-SkyMed products

Davide Nitti, Raffaele Nutricato, Rino Lorusso, Nunzia Lombardi, Fabio Bovenga, Maria Bruno, Maria Chiaradia, Giovanni Milillo

Proceedings Volume 9642, 96420D (2015) https://doi.org/10.1117/12.2196870

KEYWORDS: Avalanche photodetectors, Synthetic aperture radar, Chromium, Sensors, Satellites, Calibration, Error analysis, Inspection, Electroluminescence, Reflectors

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Proceedings Article | 21 October 2014 Paper

Corner reflectors and multi-temporal SAR inteferometry for landslide monitoring

Fabio Bovenga, Alberto Refice, Guido Pasquariello, Davide Nitti, Raffaele Nutricato

Proceedings Volume 9243, 92430I (2014) https://doi.org/10.1117/12.2066833

KEYWORDS: Chromium, Synthetic aperture radar, Landslide (networking), Picosecond phenomena, Reflectors, Interferometry, Vegetation, Sensors, Neodymium, Autoregressive models

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Proceedings Article | 21 October 2014 Paper

Suitability of COSMO-SkyMed constellation for radargrammetric DEM generation

Domenico Conte, Fabio Bovenga, Alberto Refice, Davide Nitti, Raffaele Nutricato, Maria Chiaradia

Proceedings Volume 9243, 924302 (2014) https://doi.org/10.1117/12.2066846

KEYWORDS: Synthetic aperture radar, Interferometry, Image processing, Interferometric synthetic aperture radar, Error analysis, Satellites, Chromium, Data acquisition, Neodymium, Picosecond phenomena

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Proceedings Article | 21 October 2014 Paper

Exploitation of a large COSMO-SkyMed interferometric dataset

Raffaele Nutricato, Davide Nitti, Fabio Bovenga, Alberto Refice, Maria Chiaradia

Proceedings Volume 9243, 92430C (2014) https://doi.org/10.1117/12.2067156

KEYWORDS: LIDAR, Synthetic aperture radar, Picosecond phenomena, Avalanche photodetectors, Sensors, Satellites, Interferometry, Error analysis, Earthquakes, Data acquisition

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Proceedings Article | 17 October 2013 Paper

DEM generation by using COSMO/SkyMed tandem pairs and weather models

Davide Nitti, Fabio Bovenga, Raffaele Nutricato, Francesca Intini, Maria Teresa Chiaradia

Proceedings Volume 8891, 88910E (2013) https://doi.org/10.1117/12.2048902

KEYWORDS: Interferometry, Synthetic aperture radar, Atmospheric modeling, Sensors, Global Positioning System, Interferometric synthetic aperture radar, Atmospheric sensing, 3D modeling, Statistical analysis, Satellites

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Proceedings Article | 17 October 2013 Paper

C/X-band SAR interferometry applied to ground monitoring: examples and new potential

Raffaele Nutricato, Davide Nitti, Fabio Bovenga, Alberto Refice, Janusz Wasowski, Maria Chiaradia

Proceedings Volume 8891, 88910C (2013) https://doi.org/10.1117/12.2029096

KEYWORDS: Synthetic aperture radar, X band, Picosecond phenomena, Sensors, Landslides, Interferometry, Spatial resolution, Data acquisition, Interferometric synthetic aperture radar, Buildings

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Proceedings Article | 21 November 2012 Paper

Multi-chromatic analysis of a single SAR image for absolute ranging

Fabio Bovenga, Leonardo Gallitelli, Davide Nitti

Proceedings Volume 8536, 853604 (2012) https://doi.org/10.1117/12.973722

KEYWORDS: Synthetic aperture radar, Image processing, Satellites, Roentgenium, Chromium, Sensors, Atmospheric modeling, Error analysis, Reflectors, Ranging

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Proceedings Article | 19 October 2012 Paper

On the use of SAR interferometry to aid navigation of UAV

Davide Nitti, Fabio Bovenga, Alberto Morea, Fabio Rana, Luciano Guerriero, Mario Greco, Gianpaolo Pinelli

Proceedings Volume 8532, 853203 (2012) https://doi.org/10.1117/12.974563

KEYWORDS: Interferometry, Synthetic aperture radar, Interferometric synthetic aperture radar, Phase interferometry, Unmanned aerial vehicles, Error analysis, Interferometers, Global Positioning System, Data modeling, Radar

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Proceedings Article | 23 October 2010 Paper

Multi-temporal DInSAR analysis with X-band high resolution SAR data: examples and potential

Fabio Bovenga, Davide Oscar Nitti, Alberto Refice, Raffaele Nutricato, Maria Teresa Chiaradia

Proceedings Volume 7829, 78290I (2010) https://doi.org/10.1117/12.866459

KEYWORDS: X band, Sensors, Synthetic aperture radar, Picosecond phenomena, Image sensors, Data modeling, Interferometry, Image processing, Remote sensing, Atmospheric modeling

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Proceedings Article | 5 October 2009 Paper

C- and X-band multi-pass InSAR analysis over alpine areas (ITALY)

Davide Oscar Nitti, Fabio Bovenga, Raffaele Nutricato, Fabio Rana, Crescenza D'Aprile, Paolo Frattini, Giovanni Crosta, Maria Teresa Chiaradia, Giovanna Ober, Laura Candela

Proceedings Volume 7477, 74771Q (2009) https://doi.org/10.1117/12.849210

KEYWORDS: Synthetic aperture radar, X band, Interferometry, Landslide (networking), Picosecond phenomena, Interferometric synthetic aperture radar, Satellites, Image processing, Spatial resolution, Sensors

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In the present work we present first results of ground deformation measurements inferred through repeat-pass Synthetic Aperture Radar (SAR) Interferometry (InSAR) in C- and X-band over an Italian Alpine area, in Lombardia region. The activity was carried out in the framework of the MORFEO (MOnitoraggio e Rischio da Frana mediante dati EO) project founded by the Italian Spatial Agency (ASI) and dedicated to landslide risk assessment. A number of areas affected by hydrogeological instabilities have been selected and studied in detail by processing both C- and X-band SAR data through SPINUA, a Persistent Scatterer like algorithm. In particular, two stacks of 30 Ascending ENVISAT SAR images (October 2004 - January 2009) and 32 Descending ENVISAT SAR images (December 2004 - January 2009) have been independently processed to ensures the detection of movements occurring along both west and east facing slopes. Moreover, further deformation measurements have been obtained by processing a set of 12 COSMO-SkyMED ascending HIMAGE interferometric acquisitions (Satellite CSKS1; Beam HI-03; POL: HH; Incidence Angle: 29°) provided by ASI. After a proper tuning of the interferometric algorithmic solutions, even with very high normal baselines, we are able to appreciate the potentials of X-band interferometry. Although the number of COSMO-SkyMED acquisitions is quite limited, spanning a period of only 10 months (August 2008 - June 2009), SPINUA was capable to retrieve preliminary ground displacement patterns that are in good agreement with those previously estimated in C-band. Quite impressive is to realize that, because of the tenfold improved resolution of X-band images, multi-temporal InSAR techniques may be successfully applied for the estimation of the displacement maps with a number of acquisitions much lower than in C-band. InSAR-derived displacements provided on areas of hydrogeological interest are going to be validated in the framework of MORFEO project by the geological partnership thanks to the availability of ground truths. In the present work, we present the results obtained on the towns of Garzeno, Catasco and Germasino which are affected by landslide phenomena. We provide a first validation by comparing the deformation maps derived from ENVISAT C-band data, from COSMO-SkyMED X-band data as well as from ERS and RADARSAT C-band data freely available on the GeoIFFI web-catalogue.

Proceedings Article | 29 September 2009 Paper

TerraSAR-X InSAR multipass analysis on Venice (Italy)

D. Nitti, R. Nutricato, F. Bovenga, A. Refice, M. Chiaradia, L. Guerriero

Proceedings Volume 7477, 74771I (2009) https://doi.org/10.1117/12.832047

KEYWORDS: Synthetic aperture radar, Interferometry, Interferometric synthetic aperture radar, X band, Sensors, Picosecond phenomena, Stanford Linear Collider, Image processing, Satellites, Spatial resolution

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The TerraSAR-X (copyright) mission, launched in 2007, carries a new X-band Synthetic Aperture Radar (SAR) sensor optimally suited for SAR interferometry (InSAR), thus allowing very promising application of InSAR techniques for the risk assessment on areas with hydrogeological instability and especially for multi-temporal analysis, such as Persistent Scatterer Interferometry (PSI) techniques, originally developed at Politecnico di Milano. The SPINUA (Stable Point INterferometry over Unurbanised Areas) technique is a PSI processing methodology which has originally been developed with the aim of detection and monitoring of coherent PS targets in non or scarcely-urbanized areas. The main goal of the present work is to describe successful applications of the SPINUA PSI technique in processing X-band data. Venice has been selected as test site since it is in favorable settings for PSI investigations (urban area containing many potential coherent targets such as buildings) and in view of the availability of a long temporal series of TerraSAR-X stripmap acquisitions (27 scenes in all). The Venice Lagoon is affected by land sinking phenomena, whose origins are both natural and man-induced. The subsidence of Venice has been intensively studied for decades by determining land displacements through traditional monitoring techniques (leveling and GPS) and, recently, by processing stacks of ERS/ENVISAT SAR data. The present work is focused on an independent assessment of application of PSI techniques to TerraSAR-X stripmap data for monitoring the stability of the Venice area. Thanks to its orbital repeat cycle of only 11 days, less than a third of ERS/ENVISAT C-band missions, the maximum displacement rate that can be unambiguously detected along the Line-of-Sight (LOS) with TerraSAR-X SAR data through PSI techniques is expected to be about twice the corresponding value of ESA C-band missions, being directly proportional to the sensor wavelength and inversely proportional to the revisit time. When monitoring displacement phenomena which are known to be within the C-band rate limits, the increased repeat cycle of TerraSAR-X offers the opportunity to decimate the stack of TerraSAR-X data, e.g. by doubling the temporal baseline between subsequent acquisitions. This strategy can be adopted for reducing both economic and computational processing costs. In the present work, the displacement rate maps obtained through SPINUA with and without decimation of the number of Single Look Complex (SLC) acquisitions are compared. In particular, it is shown that with high spatial resolution SAR data, reliable displacement maps could be estimated through PSI techniques with a number of SLCs much lower than in C-band.

Proceedings Article | 10 October 2008 Paper

Evaluation of DEM-assisted SAR coregistration

D. Nitti, R. Hanssen, A. Refice, F. Bovenga, G. Milillo, R. Nutricato

Proceedings Volume 7109, 710919 (2008) https://doi.org/10.1117/12.802767

KEYWORDS: Synthetic aperture radar, Satellites, Interferometry, X band, Sensors, Spherical lenses, Picosecond phenomena, Error analysis, Radar, Stanford Linear Collider

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Image alignment is without doubt the most crucial step in SAR Interferometry. Interferogram formation requires images to be coregistered with an accuracy of better than 1/8 pixel to avoid significant loss of phase coherence. Conventional interferometric precise coregistration methods for full-resolution SAR data (Single-Look Complex imagery, or SLC) are based on the cross-correlation of the SLC data, either in the original complex form or as squared amplitudes. Offset vectors in slant range and azimuth directions are computed on a large number of windows, according to the estimated correlation peaks. Then, a two-dimensional polynomial of a certain degree is usually chosen as warp function and the polynomial parameters are estimated through LMS fit from the shifts measured on the image windows. In case of rough topography and long baselines, the polynomial approximation for the warp function becomes inaccurate, leading to local misregistrations. Moreover, these effects increase with the spatial resolution and then with the sampling frequency of the sensor, as first results on TerraSAR-X interferometry confirm. An improved, DEM-assisted image coregistration procedure can be adopted for providing higher-order prediction of the offset vectors. Instead of estimating the shifts on a limited number of patches and using a polynomial approximation for the transformation, this approach computes pixel by pixel the correspondence between master and slave by using the orbital data and a reference DEM. This study assesses the performance of this approach with respect to the standard procedure. In particular, both analytical relationships and simulations will evaluate the impact of the finite vertical accuracy of the DEM on the final coregistration precision for different radar postings and relative positions of satellites. The two approaches are compared by processing real data at different carrier frequencies and using the interferometric coherence as quality figure.

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