A Framework for SAR-Optical Stereogrammetry over Urban Areas

Currently, numerous remote sensing satellites provide a huge volume of diverse earth observation data. As these data show different features regarding resolution, accuracy, coverage, and spectral imaging ability, fusion techniques are required to integrate the different properties of each sensor and produce useful information. For example, synthetic aperture radar (SAR) data can be fused with optical imagery to produce 3D information using stereogrammetric methods. The main focus of this study is to investigate the possibility of applying a stereogrammetry pipeline to very-high-resolution (VHR) SAR-optical image pairs. For this purpose, the applicability of semi-global matching is investigated in this unconventional multi-sensor setting. To support the image matching by reducing the search space and accelerating the identification of correct, reliable matches, the possibility of establishing an epipolarity constraint for VHR SAR-optical image pairs is investigated as well. In addition, it is shown that the absolute geolocation accuracy of VHR optical imagery with respect to VHR SAR imagery such as provided by TerraSAR-X can be improved by a multi-sensor block adjustment formulation based on rational polynomial coefficients. Finally, the feasibility of generating point clouds with a median accuracy of about 2m is demonstrated and confirms the potential of 3D reconstruction from SAR-optical image pairs over urban areas.Comment: This is the pre-acceptance version, to read the final version, please go to ISPRS Journal of Photogrammetry and Remote Sensing on ScienceDirec

Open source tool for DSMs generation from high resolution optical satellite imagery. Development and testing of an OSSIM plug-in

The fully automatic generation of digital surface models (DSMs) is still an open research issue. From recent years, computer vision algorithms have been introduced in photogrammetry in order to exploit their capabilities and efficiency in three-dimensional modelling. In this article, a new tool for fully automatic DSMs generation from high resolution satellite optical imagery is presented. In particular, a new iterative approach in order to obtain the quasi-epipolar images from the original stereopairs has been defined and deployed. This approach is implemented in a new Free and Open Source Software (FOSS) named Digital Automatic Terrain Extractor (DATE) developed at the Geodesy and Geomatics Division, University of Rome ‘La Sapienza’, and conceived as an Open Source Software Image Map (OSSIM) plug-in. DATE key features include: the epipolarity achievement in the object space, thanks to the images ground projection (Ground quasi-Epipolar Imagery (GrEI)) and the coarse-to-fine pyramidal scheme adopted; the use of computer vision algorithms in order to improve the processing efficiency and make the DSMs generation process fully automatic; the free and open source aspect of the developed code. The implemented plug-in was validated through two optical datasets, GeoEye-1 and the newest Pléiades-high resolution (HR) imagery, on Trento (Northern Italy) test site. The DSMs, generated on the basis of the metadata rational polynomial coefficients only, without any ground control point, are compared to a reference lidar in areas with different land use/land cover and morphology. The results obtained thanks to the developed workflow are good in terms of statistical parameters (root mean square error around 5 m for GeoEye-1 and around 4 m for Pléiades-HR imagery) and comparable with the results obtained through different software by other authors on the same test site, whereas in terms of efficiency DATE outperforms most of the available commercial software. These first achievements indicate good potential for the developed plug-in, which in a very near future will be also upgraded for synthetic aperture radar and tri-stereo optical imagery processing

Towards Automatic SAR-Optical Stereogrammetry over Urban Areas using Very High Resolution Imagery

In this paper we discuss the potential and challenges regarding SAR-optical stereogrammetry for urban areas, using very-high-resolution (VHR) remote sensing imagery. Since we do this mainly from a geometrical point of view, we first analyze the height reconstruction accuracy to be expected for different stereogrammetric configurations. Then, we propose a strategy for simultaneous tie point matching and 3D reconstruction, which exploits an epipolar-like search window constraint. To drive the matching and ensure some robustness, we combine different established handcrafted similarity measures. For the experiments, we use real test data acquired by the Worldview-2, TerraSAR-X and MEMPHIS sensors. Our results show that SAR-optical stereogrammetry using VHR imagery is generally feasible with 3D positioning accuracies in the meter-domain, although the matching of these strongly hetereogeneous multi-sensor data remains very challenging. Keywords: Synthetic Aperture Radar (SAR), optical images, remote sensing, data fusion, stereogrammetr

FOSS4G DATE for DSMs generation from tri-stereo optical satellite images: development and first results

The topic of this research is the identification of an innovative strategy for DSMs generation from optical satellite tri-stereo imagery, exploiting efficient dense matching algorithms from computer vision, without losing a rigorous photogrammetric approach. The main challenge is related to the epipolarity resampling for satellite images, for which it is not straightforward the epipolar geometry achievement, due to their multiple projection centres. The Ground quasi-Epipolar Images (GrEI) are the core of this original strategy for DSMs generation, able to return reliable and accurate solutions. The FOSS4G DATE has been modified since its original implementation, in order to obtain better results in terms of DSMs generated, and a new version has been released. The workflow provides a ground projection for the raw satellite images, exploiting RPFs model and a coarse DSM. In order to bring the ground images in the quasi-epipolar geometry, a preliminary rotation is estimated for both images to align them in the disparity prevailing direction. Then, a refinement of their relative position is performed. These orthorectified images can act as GrEI, and can undergo a dense image matching procedure. Tests have been carried out with Pléiades triplets over Trento (Northern Italy) and very good results are achieved

Extraction of digital surface models from corona satellite stereo images

Satellite images can be utilised for observing surf icial changes, especially efficient in the monitoring of larger areas. The comparative analysis of high resolution images from earlier periods with recent data can provide insight in the scale of changes in topography, and with meteorological, hydrological and other historic records, can lead to better understanding and more reliable modelling of the predominant processes causing mass movement. More accurate morphometric and visual analysis of the topographic changes is possible using digital surface model (DSM), which can be obtained from satellite stereo images. In this paper, the authors evaluated methods of creation digital surface models obtained from satellite images from the CORONA program in monitoring surfic ial massmovement processes in the Fruška Gora mountain area , in the southern part of the Vojvodina province in Serbia. This area is of particular interest because of its favourable geographic location, rich geo- and cultural heritage and increasing demand for exploitation, which results in greater impact of natural hazards. The CORONA images were chosen because of good availability of high resolution coverage for the whole area from the period of past four decades

Extraction of digital surface models from corona satellite stereo images

Satellite images can be utilised for observing surf icial changes, especially efficient in the monitoring of larger areas. The comparative analysis of high resolution images from earlier periods with recent data can provide insight in the scale of changes in topography, and with meteorological, hydrological and other historic records, can lead to better understanding and more reliable modelling of the predominant processes causing mass movement. More accurate morphometric and visual analysis of the topographic changes is possible using digital surface model (DSM), which can be obtained from satellite stereo images. In this paper, the authors evaluated methods of creation digital surface models obtained from satellite images from the CORONA program in monitoring surfic ial massmovement processes in the Fruška Gora mountain area , in the southern part of the Vojvodina province in Serbia. This area is of particular interest because of its favourable geographic location, rich geo- and cultural heritage and increasing demand for exploitation, which results in greater impact of natural hazards. The CORONA images were chosen because of good availability of high resolution coverage for the whole area from the period of past four decades

Extraction of digital surface models from CORONA satellite stereo images

Satellite images can be utilised for observing surficial changes, especially efficient in the monitoring of larger areas. The comparative analysis of high resolution images from earlier periods with recent data can provide insight in the scale of changes in topography, and with meteorological, hydrological and other historic records, can lead to better understanding and more reliable modelling of the predominant processes causing mass movement. More accurate morphometric and visual analysis of the topographic changes is possible using digital surface model (DSM), which can be obtained from satellite stereo images. In this paper, the authors evaluated methods of creation digital surface models obtained from satellite images from the CORONA program in monitoring surficial mass movement processes in the Fruška Gora mountain area, in the southern part of the Vojvodina province in Serbia. This area is of particular interest because of its favourable geographic location, rich geo- and cultural heritage and increasing demand for exploitation, which results in greater impact of natural hazards. The CORONA images were chosen because of good availability of high resolution coverage for the whole area from the period of past four decades