Building profile reconstruction using TerraSAR-X data time-series and tomographic techniques

This work aims to show the potentialities of SAR Tomography (TomoSAR) techniques for the 3-D characterization (height, reflectivity, time stability) of built-up areas using data acquired by the satellite sensor TerraSAR-X. For this purpose 19 TerraSAR-X single-polarimetric multibaseline images acquired over Paris urban area have been processed applying classical nonparametric (Beamforming and Capon) and parametric (MUSIC) spectral estimation techniques

Génération des modèles numériques de la surface sur les zones urbaines au moyen des images satellitaires SAR à haute résolution : techniques tomographiques et leur application à la surveillance des changements 3-D

The urbanization and the management of urban environment and its periphery become one of the most crucial issues in developed and developing countries. In these circumstances, remote sensing data are an important source of information that reflects interactions between human beings and their environment. Given their complete independence from logistic constraints on the ground, illumination (daylight), and weather (clouds) conditions, Synthetic Aperture Radar (SAR) satellite systems may provide important contributions in complex environments 3-D reconstruction. The new generation of high resolution SAR sensors as COSMO-SkyMed, TerraSAR-X and RADARSAT-2 allowed to acquire high resolution SAR imagery. Here the attention is put on the 3-D imaging technique called SAR Tomography: starting from a stack of images collected using multibaseline data performed in interferometric configuration, such a technique allows to retrieve height information forming a synthetic aperture in the elevation direction in order to achieve a substantially improved resolution. The present PhD thesis is focused on the high potentialities of tomographic techniques in 3-D change monitoring and characterization for complex and dense built-up areas using basic mono-dimensional estimators as Beamforming, Capon and MUSIC combined to very high satellite SAR resolution imagery. 2-D and 3-D analysis have been presented over the urban area of Paris using TerraSAR-X data at high resolution and single polarisation. Being mainly focused on the 3-D tomographic techniques, in the presented work 4-D methods, such as compressive sensing (CS), have not been taken into account. At first, the analysis of the interferometric quality of the processed data set has been performed and results showed good mean coherence values within the entire stack. The extraction of 2-D tomograms over different azimuth-profile has showed the capabilities to distinguish more than one scatterer within the same resolution cell and to reconstruct the vertical building profiles. Successively, a global 3-D characterization both in term of buildings heights and vertical reflectivity has been performed in order to develop a monitoring tool for the changes of single structures. Moreover, the possibility to correct the geometric distortions due to the layover (that strongly affects such kind of scenarios) and to determine the information about the number of scatterers (up to three) and the corresponding reflectivity within one resolution cell have been evaluated. Moreover an innovative time stability analysis of the observed scene have been carried out in order to detect the stable and unstable scatterers. Globally, the investigations showed noisier and sparser point clouds for the Capon method, whereas better capabilities for the Beamforming and MUSIC ones. Indeed, it was possible to detect different scatterers located within the same resolution cell and to resolve pixels affected by the layover. This has lead to perform a good reconstruction of building shape and location and a good estimation of their elevation. The 3-D time stability analysis demonstrated the possibility to monitor the 3-D change depending on the time. Eventually, it is possible to assert that processing high resolution SAR data allows to achieve a strong improvement in 3-D imaging capabilities. It has been demonstrated the potentialities of TomoSAR technique in distortions correction and in 3-D change monitoring using basic mono-dimensional estimators.L'urbanisation et la gestion de l'environnement urbain et sa périphérie deviennent l'un des problèmes les plus cruciaux dans les pays développés et en développement. Dans ces circonstances, les données de télédétection sont une source importante d'information qui reflète les interactions entre les êtres humains et leur environnement. Compte tenu de leur indépendance totale des contraintes logistiques sur le terrain, l'éclairage (lumière du jour) et météorologiques (nuages) conditions, Synthetic Aperture Radar (SAR) les systèmes de satellites peuvent fournir des contributions importantes dans des environnements complexes de reconstruction 3-D. La nouvelle génération de haute résolution SAR capteurs comme COSMOSkyMed, TerraSAR-X RADARSAT-2 a permis d'acquérir des images SAR à haute résolution. Ici, l'attention est mis sur la technique pour l'imagerie 3-D nominée tomographie SAR: à partir d'une pile d'images ont été recueillies en utilisant les données multibaseline effectuées dans la configuration interférométrique, une telle technique permet d'extraire les informations de hauteur formant une ouverture synthétique dans la direction d'élévation afin d'obtenir une résolution sensiblement améliorée. Cette thèse de doctorat se concentre sur les potentialités élevées de techniques tomographiques en 3-D surveillance des changements et la caractérisation des zones complexes et denses bâties en utilisant des estimateurs mono-dimensionnelle de base comme Beamforming, Capon et MUSIC combinée au satellite très haute résolution des images SAR. 2-D et de l'analyse 3-D ont été présentés sur la zone urbaine de Paris en utilisant les données TerraSAR-X à haute résolution et de polarisation unique. Être porté principalement sur les techniques tomographiques 3-D, dans les méthodes de travail 4-D présentés, tels que le Compressive Sensing, ne sont pas pris en compte. Dans un premier temps, l'analyse de la qualité interférométrique de l'ensemble de données transformées a montré de bonnes valeurs de cohérence moyenne et ont permis de détecter des images considérées comme des valeurs aberrantes. L'extraction des tomographies 2-D sur l'azimut différent de profil a montré la capacité de distinguer plus d'un diffuseur à l'intérieur de la même cellule de résolution et de reconstituer les profilés de construction verticaux. Successivement, une caractérisation 3-D globale en terme de bâtiments hauteurs et réflectivité verticale a été réalisée dans le but de développer un outil de suivi des changements des structures simples. En outre, la possibilité de corriger les distorsions géométriques en raison de l'escale (qui affecte fortement ce genre de scénarios) et de déterminer les informations sur le nombre de diffuseurs (jusqu'à trois) et la réflectivité correspondant à l'intérieur d'une cellule de résolution ont été évalués

Building profile reconstruction using TerraSAR-X data time-series and tomographic techniques

International audienceThis work aims to show the potentialities of SAR Tomography (TomoSAR) techniques for the 3-D characterization (height, reflectivity, time stability) of built-up areas using data acquired by the satellite sensor TerraSAR-X. For this purpose 19 TerraSAR-X single-polarimetric multibaseline images acquired over Paris urban area have been processed applying classical non-parametric (Beamforming and Capon) and parametric (MUSIC) spectral estimation techniques

Radargrammetric digital surface models generation from high resolution satellite SAR imagery: Methodology and case studies

The goal of this paper is to investigate the potential of high resolution SAR satellite imagery for DSMs generation using the radargrammetric technique. This study is methodological, devoted to illustrate both the fundamental advantages of this approach and also its drawbacks. As for photogrammetry, the achievable accuracy level of a radargrammetric generated DSM is strictly related both to the image orientation and to the image matching procedure. A rigorous orientation model based only on metadata information and an innovative matching strategy have been developed, so that a complete suite for the DSMs generation through radargrammetry has been embedded in SISAR, a scientific software developed at the Geodesy and Geomatic Division of the University of Rome “La Sapienza”. Here we discuss the results coming from two COSMO-SkyMed SpotLight stereo pairs (ascending and descending) acquired over the area of Como (Northern Italy), characterized by a mixed land cover (flat urban area, steep forested mountain slopes). Three DSMs (ascending, descending and merged) have been generated and compared with a LiDAR DSM; the accuracy of the merged product is around 7m, better than the accuracy of the ascending and descending DSMs (around 8–10 m)

Fast terrain modelling for hydrogeological risk mapping and emergency management: the contribution of high-resolution satellite SAR imagery

Geomatic tools fast terrain modelling play a relevant role in hydrogeological risk mapping and emergency management. Given their complete independence from logistic constraints on the ground (as for airborne data collection), illumination (daylight), and weather (clouds) conditions, synthetic aperture radar (SAR) satellite systems may provide important contributions in terms of digital surface models (DSMs) and digital elevation models (DEMs).For this work we focused on the potential of high-resolution SAR satellite imagery for DSM generation using an interferometric (InSAR) technique and using a revitalized radargrammetric stereomapping approach. The goal of this work was just methodological. Our goal was to illustrate both the fundamental advantages and drawbacks of the radargrammetric approach with respect to the InSAR technique for DSM generation, and to outline their possible joint role in hydrogeological risk mapping and emergency management. Here, it is worth mentioning that radargrammetry procedures are independent of image coherence (unlike the interferometric approach) and phase unwrapping, as well as of parsimony (only a few images are necessary). Therefore, a short time is required for image collection (from tens of minutes to a few hours), thanks to the independence from illumination and weather. The most relevant obstacles of the technique are speckle and the lack of texture impact on image matching, as well as the well-known deformations of SAR imagery (layover and foreshortening), which may produce remarkable difficulties with complex morphologies and that must be accounted for during acquisition planning.Here, we discuss results obtained with InSAR and radargrammetry applied to a COSMO-SkyMed SpotLight triplet (two stereopairs suited for radargrammetry and InSAR, sharing one common image) acquired over suburbs of San Francisco (United States), which are characterized by mixed morphology and land cover. We mainly focused on urban areas and zones covered by bare soil and rocks. Image processing was performed using the well-known commercial software SARscape® for InSAR, and the radargrammetric suite implemented in SISAR, software developed at the Geodesy and Geomatic Division of the University of Rome "La Sapienza".Global accuracies were approximately 5 m using both approaches. However, several differences in terrain morphology reconstruction were determined and are underlined and evaluated here, as well as a possible way to further enhance the results using the integration of InSAR and radargrammetry. © 2014 © 2014 Taylor & Francis

Evaluation and comparison of different radargrammetric approaches for Digital Surface Models generation from COSMO-SkyMed, TerraSAR-X, RADARSAT-2 imagery: Analysis of Beauport (Canada) test site

In this manuscript we analyze the potentialities of the radargrammetric DSMs generation using high resolution SAR imagery acquired by three different platforms (COSMO-SkyMed, TerraSAR-X and RADARSAT-2), with particular attention to geometric orientation models. Two orientation models are considered and compared: Toutin's model (Canada Center for Remote Sensing), implemented in the commercial software package PCI-Geomatica and based on Ground Control Points (GCPs), and the radargrammetric model implemented in the scientific software SISAR (University of Rome La Sapienza), based on images metadata orbital information only. Moreover, a comparison between the DSMs following the image matching approaches implemented in PCI-Geomatica and SISAR has been performed. The analysis has been carried out over Beauport test site (Quebec, Canada), where three overlapping stereopairs, one for each of the mentioned platform, were acquired and a LiDAR ground truth and a dense set of GNSS Check points (CPs) are available. The presented results appear promising: DSMs accuracy are within 4 and 5 m for all sensors, independently from orientation model (with or without GCP) and image matching approach, provided good relative orientation is guaranteed, what mainly attains to the quality of metadata orbital information. (C) 2014 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS)

Fast terrain modeling for hydrogeological risk mapping and emergency management: the contribution of high resolution satellite SAR imagery

Geomatic tools for fast terrain modelling play a relevant role both for hydrogeological risk mapping and for hydrogeological emergency management. Among these tools, Synthetic Aperture Radar (SAR) satellite systems may give important contributions in terms of Digital Surface Models (DSMs) and Digital Elevation Models (DEMs), considering their complete independence from logistic constraints on the ground (as for airborne data collection), illumination (daylight) and weather (clouds) conditions. Here we focus on the present potentialities of high resolution SAR satellite imagery for DSMs generation with the radargrammetric stereo-mapping approach and with the well-known interferometric technique. Therefore, the goal of this paper is just methodological, devoted to illustrate both the fundamental advantages of radargrammetric approach and also its drawbacks respect to the InSAR technique. As regards the pros, it is worth to mention the independence from image coherence (unlike interferometric approach), the parsimony (it can work with just a couple of images), and therefore the short time required for imagery collection (from tens of minutes to few hours) also thanks to the mentioned independence from illumination and weather. Concerning the cons, the well known deformations of SAR imagery (layover and foreshortening) may cause remarkable difficulties with complex morphologies and have to be duly accounted for the acquisition planning. A suite for the DSMs generation through the radargrammetric approach has been implemented in SISAR (Software per Immagini Satellitari ad Alta Risoluzione), a scientific software developed at the Geodesy and Geomatic Division of the University of Rome La Sapienza. In order to demonstrate the radargrammetric mapping potentialities of high resolution SAR satellite imagery, several tests were carried out using data with different features (SpotLight, StripMap) coming from different platforms (COSMO-SkyMed, TerraSAR-X). Here we discuss the results obtained with a COSMO-SkyMed SpotLight stereo-pairs related to the San Francisco area, which is characterized by mixed morphology and land cover; we mainly focused on urban areas and zones covered by bare soil and rocks. Overall, accuracies range from 3 m over bare soil to about 4 m over more complex morphology, whereas they decrease in presence of remarkable image deformations

Increased serum Dickkopf-1 levels in drug-abusing psychotic patients

Background: Dickkopf-1 (DKK1) is an inhibitor of the canonical Wnt pathway, which is known to be impaired in both psychotic and neurodegenerative disorders. Here, we examined serum DKK1 levels as an indicator of ongoing neurodegeneration in psychotic patients, with or without a recent or current history of drug abuse. Methods: We measured serum DKK1 levels by ELISA in 22 inpatients with psychosis and no history of drug abuse, 22 with psychosis and drug abuse, and 16 controls. We rated psychopathology using the following rating scales: the Positive and Negative Syndrome Scale (PANSS); the Clinical Global Impressions (CGI) severity scale; and the Global Assessment of Functioning (GAF) scale. Extrapyramidal motor symptoms were assessed by the Simpson-Angus Neurological Rating Scale (NRS). Results: Inpatients with psychosis and comorbid substance abuse showed significantly higher serum DKK1 levels than inpatients with psychosis and no comorbid substance abuse or controls. Comorbid patients had earlier onset, longer duration of psychosis, and more severe extrapyramidal motor symptoms. However, we did not find any significant correlation between DKK1 levels and rating scale scores. Conclusion: Psychosis led to elevated serum DKK1 levels, and substance abuse led to a further increase. Knowing that there is a correlation between brain and blood levels of DKK1, we speculate that the observed increase in DKK1 levels reflects drug-induced neurotoxicity in our patients. (C) 2011 Elsevier Inc. All rights reserved