30 research outputs found
The SARptical Dataset for Joint Analysis of SAR and Optical Image in Dense Urban Area
The joint interpretation of very high resolution SAR and optical images in
dense urban area are not trivial due to the distinct imaging geometry of the
two types of images. Especially, the inevitable layover caused by the
side-looking SAR imaging geometry renders this task even more challenging. Only
until recently, the "SARptical" framework [1], [2] proposed a promising
solution to tackle this. SARptical can trace individual SAR scatterers in
corresponding high-resolution optical images, via rigorous 3-D reconstruction
and matching. This paper introduces the SARptical dataset, which is a dataset
of over 10,000 pairs of corresponding SAR, and optical image patches extracted
from TerraSAR-X high-resolution spotlight images and aerial UltraCAM optical
images. This dataset opens new opportunities of multisensory data analysis. One
can analyze the geometry, material, and other properties of the imaged object
in both SAR and optical image domain. More advanced applications such as SAR
and optical image matching via deep learning [3] is now also possible.Comment: This manuscript was submitted to IGARSS 201
Reconstruction of building façades using spaceborne multiview TomoSAR point clouds
In this paper we present an approach that allows automatic reconstruction of building façades from 4D point cloud generated from tomographic SAR processing. The approach is modular and works by extracting façade points from the point density projected onto the ground plane. Individual façades are segmented using an unsupervised clustering procedure. Surface (flat or curved) model parameters of the segmented building façades are further estimated and finally the geometric primitives such as intersection points of the adjacent façades are determined to complete the reconstruction process. The proposed approach is illustrated and validated by examples using TomoSAR point clouds generated from TerraSAR-X high resolution spotlight images
Non-Local Compressive Sensing Based SAR Tomography
Tomographic SAR (TomoSAR) inversion of urban areas is an inherently sparse
reconstruction problem and, hence, can be solved using compressive sensing (CS)
algorithms. This paper proposes solutions for two notorious problems in this
field: 1) TomoSAR requires a high number of data sets, which makes the
technique expensive. However, it can be shown that the number of acquisitions
and the signal-to-noise ratio (SNR) can be traded off against each other,
because it is asymptotically only the product of the number of acquisitions and
SNR that determines the reconstruction quality. We propose to increase SNR by
integrating non-local estimation into the inversion and show that a reasonable
reconstruction of buildings from only seven interferograms is feasible. 2)
CS-based inversion is computationally expensive and therefore barely suitable
for large-scale applications. We introduce a new fast and accurate algorithm
for solving the non-local L1-L2-minimization problem, central to CS-based
reconstruction algorithms. The applicability of the algorithm is demonstrated
using simulated data and TerraSAR-X high-resolution spotlight images over an
area in Munich, Germany.Comment: 10 page
Towards SAR Tomographic Inversion via Sparse Bayesian Learning
Existing SAR tomography (TomoSAR) algorithms are mostly based on an inversion
of the SAR imaging model, which are often computationally expensive. Previous
study showed perspective of using data-driven methods like KPCA to decompose
the signal and reduce the computational complexity. This paper gives a
preliminary demonstration of a new data-driven method based on sparse Bayesian
learning. Experiments on simulated data show that the proposed method
significantly outperforms KPCA methods in estimating the steering vectors of
the scatterers. This gives a perspective of data-drive approach or combining it
with model-driven approach for high precision tomographic inversion of large
areas.Comment: accepted in preliminary version for EUSAR2020 conferenc
Evaluation of insar dem from high-resolution spaceborne sar data
In recent years a new generation of high-resolution SAR satellites became operational like the Canadian Radarsat-2, the Italian Cosmo/Skymed, and the German TerraSAR-X systems. The spatial resolution of such devices achieves the meter domain or even below. Key products derived from remote sensing imagery are Digital Elevation Models (DEM). Based on SAR data various techniques can be applied for such purpose, for example, Radargrammetry (i.e., SAR Stereo) and SAR Interferometry (InSAR). In the framework of the ISPRS Working Group VII/2 "SAR Interferometry" a long term scientific project is conducted that aims at the validation of DEM derived from data of modern SAR satellite sensors. In this paper, we present DEM results yield for the city of Barcelona which were generated by means of SAR Interferometry.DL
ANALYSIS OF X-BAND VERY HIGH RESOLUTION PERSISTENT SCATTERER INTERFEROMETRY DATA OVER URBAN AREAS
Persistent Scatterer Interferometry (PSI) is a satellite-based Synthetic Aperture Radar (SAR) remote sensing technique used to measure and monitor land deformation from a stack of interferometric SAR images. This work concerns X-band PSI and, in particular, PSI based on very high resolution (VHR) StripMap CosmoSkyMed and TerraSAR-X SAR imagery. In fact, it mainly focuses on the technical aspects of deformation measurement and monitoring over urban areas. A key technical aspect analysed in this paper is the thermal expansion component of PSI observations, which is a result of temperature differences in the imaged area between SAR acquisitions. This component of PSI observations is particularly important in the urban environment. This is an interesting feature of PSI, which can be surely used to illustrate the high sensitivity of X-band PSI to very subtle displacements. Thermal expansion can have a strong impact on the PSI products, especially on the deformation velocity maps and deformation time series, if not properly handled during the PSI data processing and analysis, and a comprehensive discussion of this aspect will be provided in this paper. The importance of thermal expansion is related to the fact that the PSI analyses are often performed using limited stacks of images, which may cover a limited time period, e.g. several months only. These two factors (limited number of images and short period) make the impact of a non-modelled thermal expansion particularly critical. This issue will be illustrated considering different case studies based on TerraSAR-X and CosmoSkyMed PSI data. Besides, an extended PSI model which alleviates this problem will be described and case studies from the Barcelona metropolitan area will demonstrate the effectiveness of the proposed strategy
Evaluation of InSAR and TomoSAR for monitoring deformations caused by mining in a mountainous area with high resolution satellite-based SAR
Interferometric Synthetic Aperture Radar (InSAR) and Differential Interferometric Synthetic Aperture Radar (DInSAR) have shown numerous applications for subsidence monitoring. In the past 10 years, the Persistent Scatterer InSAR (PSI) and Small BAseline Subset (SBAS) approaches were developed to overcome the problem of decorrelation and atmospheric effects, which are common in interferograms. However, DInSAR or PSI applications in rural areas, especially in mountainous regions, can be extremely challenging. In this study we have employed a combined technique, i.e., SBAS-DInSAR, to a mountainous area that is severely affected by mining activities. In addition, L-band (ALOS) and C-band (ENVISAT) data sets, 21 TerraSAR-X images provided by German Aerospace Center (DLR) with a high resolution have been used. In order to evaluate the ability of TerraSAR-X for mining monitoring, we present a case study of TerraSAR-X SAR images for Subsidence Hazard Boundary (SHB) extraction. The resulting data analysis gives an initial evaluation of InSAR applications within a mountainous region where fast movements and big phase gradients are common. Moreover, the experiment of four-dimension (4-D) Tomography SAR (TomoSAR) for structure monitoring inside the mining area indicates a potential near all-wave monitoring, which is an extension of conventional InSAR
Buildings Detection in VHR SAR Images Using Fully Convolution Neural Networks
This paper addresses the highly challenging problem of automatically
detecting man-made structures especially buildings in very high resolution
(VHR) synthetic aperture radar (SAR) images. In this context, the paper has two
major contributions: Firstly, it presents a novel and generic workflow that
initially classifies the spaceborne TomoSAR point clouds generated by
processing VHR SAR image stacks using advanced interferometric techniques known
as SAR tomography (TomoSAR) into buildings and non-buildings with the aid
of auxiliary information (i.e., either using openly available 2-D building
footprints or adopting an optical image classification scheme) and later back
project the extracted building points onto the SAR imaging coordinates to
produce automatic large-scale benchmark labelled (buildings/non-buildings) SAR
datasets. Secondly, these labelled datasets (i.e., building masks) have been
utilized to construct and train the state-of-the-art deep Fully Convolution
Neural Networks with an additional Conditional Random Field represented as a
Recurrent Neural Network to detect building regions in a single VHR SAR image.
Such a cascaded formation has been successfully employed in computer vision and
remote sensing fields for optical image classification but, to our knowledge,
has not been applied to SAR images. The results of the building detection are
illustrated and validated over a TerraSAR-X VHR spotlight SAR image covering
approximately 39 km almost the whole city of Berlin with mean
pixel accuracies of around 93.84%Comment: Accepted publication in IEEE TGR