Panoramic images have increasingly interesting applications and they are extensively used for cultural heritage documentation and virtual 3D environments. Moreover, it has been proven that they can contain good metric content. This paper describes a state-of-the-art photogrammetric tool based on spherical panoramas. The fundamental photogrammetric equations are reviewed and two real applications are examined in order to illustrate its performance in terms of accuracy and efficiency. As a first step towards the automation of the orientation and restitution process, the epipolar geometry of spherical panoramic images has also been investigated. With a view to its integration in photogrammetric tools, the shape of the epipolar line is studied both in 3D space and as a 2D mapping; the results obtained with simulation data are analysed.
During the last few years, there has been a growing exploitation of consumer-grade cameras allowing one to capture 360&deg; images. Each device has different features and the choice should be entrusted on the use and the expected final output. The interest on such technology within the research community is related to its use versatility, enabling the user to capture the world with an omnidirectional view with just one shot. The potential is huge and the literature presents many use cases in several research domains, spanning from retail to construction, from tourism to immersive virtual reality solutions. However, the domain that could the most benefit is Cultural Heritage (CH), since these sensors are particularly suitable for documenting a real scene with architectural detail. Following the previous researches conducted by Fangi, which introduced its own methodology called Spherical Photogrammetry (SP), the aim of this paper is to present some tests conducted with the omni-camera Panono 360&deg; which reach a final resolution comparable with a traditional camera and to validate, after almost ten years from the first experiment, its reliability for architectural surveying purposes. Tests have been conducted choosing as study cases <i>Santa Maria della Piazza</i> and <i>San Francesco alle scale Churches</i> in Ancona, Italy, since they were previously surveyed and documented with SP methodology. In this way, it has been possible to validate the accuracy of the new survey, performed by means an omni-camera, compared with the previous one for both outdoor and indoor scenario. The core idea behind this work is to validate if this new sensor can replace the standard image collection phase, speeding up the process, assuring at the same time the final accuracy of the survey. The experiment conducted demonstrate that, w.r.t. the SP methodology developed so far, the main advantage in using 360&deg;&thinsp;omni-directional cameras lies on increasing the rapidity of acquisition and panorama creation phases. Moreover, in order to foresee the implications that a wide adoption of fast and agile tools of acquisition could bring within the CH domain, points cloud have been generated with the same panoramas and visualized in a WEB application, to allow a result dissemination between the users.
A convenient new photogrammetric technique, the Multi-Image Spherical Photogrammetry (MISP), particularly suitable for metric recording of architecture, has been set up and already used in many projects (Fangi, 2007, 2008, 2009, 2010, 2011). From a unique point of view, photographs are taken 360° around to form a spherical panorama. This panorama is suitable for measurements. The advantages in comparison with traditional pin-hole photogrammetry are many: the speed of the survey, the low-cost of the system, the drastic reduction of the photogrammetric models. The disadvantages consist in the fact that the only suitable points for plotting are those easily identifiable in the different panoramas, because of lack of stereoscopy. In order to solve this problem the following steps have been made: To use web service of Photosynth to get the orientation of a flurry of photos [27]; To generate dense point cloud by PMVS-2 (Furukawa,[28]); To edit the point cloud with Mesh Lab, an open source software [26]; To employ a suite of modeling programs to create a 3D model of the church.
Syria is a country of many civilizations, Marie, Aramaic, Phoenician, Roman, Byzantine, Islamic, Ottoman civilizations. Unfortunally the recent war is the reason for many cultural heritage items to be destroyed, beyond the thausand civilian people killed. In 2010, just before the war, the A. made a touristic trip together with Crua (Recreational Club of the Ancona University). It was the occasion to make some fast documentation of some Syrian CH monuments. Mostly of the images were taken by the A. not to make a survey, but as a photographic report, as fast and complete as possible. For a regular survey project, the tripod, the spherical head should be used for the takings and the 3x3 Cipa rules should be followed, that occurred only in the three main projects, say the survey of the citadel walls in Aleppo, the survey of the Umayyads Mosque in Damascus, and the survey of the minaret of the Umayyads Mosque in Aleppo. All the other documentation surveys have been carried out with hand-held camera taking the dimension of the model from Google earth high resolution, when available. But, apart the regular surveys, due to the explosion of the unexpected war, the photographs taken in such a touristic way, have been used to try to get some usable plottings an restitutions and it worked successfully mostly of the times. These surveys could be useful in case of reconstruction and in case of lack of suitable alternative metric documentation. Because of the continuing threats, all six Syrian World Heritage properties were inscribed on the List of World Heritage in Danger, at the 37th session of the World Heritage Committee, held in Cambodia last June: Ancient City of Aleppo, Ancient City of Bosra, Ancient City of Damascus, Ancient Villages of Northern Syria, Krak des Chevaliers and Qal’at Salah El-Din ans finally the Site of Palmyra. See the following links: <a href="https://www.youtube.com/watch?feature=player_embedded&v=kr.a3e0DL5sA"target="_blank">https://www.youtube.com/watch?feature=player_embedded&v=kr.a3e0DL5sA</a> and <a href="https://www.youtube.com/watch?v=ltFFjjrUgtU"target="_blank">https://www.youtube.com/watch?v=ltFFjjrUgtU</a>. Apart the Ancient Villages of Northern Syria, the A. visited all the World Heritage sites and partly documented. Some of them have already been plotted, some are in the orientation stage, some have been documented only.
ABSTRACT:This paper exploits the potential of dense multi-image 3d reconstruction of destroyed cultural heritage monuments by either using public domain touristic imagery only or by combining the public domain imagery with professional panoramic imagery. The focus of our work is placed on the reconstruction of the temple of Bel, one of the Syrian heritage monuments, which was destroyed in September 2015 by the so called "Islamic State". The great temple of Bel is considered as one of the most important religious buildings of the 1st century AD in the East with a unique design. The investigations and the reconstruction were carried out using two types of imagery. The first are freely available generic touristic photos collected from the web. The second are panoramic images captured in 2010 for documenting those monuments. In the paper we present a 3d reconstruction workflow for both types of imagery using state-of-the art dense image matching software, addressing the non-trivial challenges of combining uncalibrated public domain imagery with panoramic images with very wide base-lines. We subsequently investigate the aspects of accuracy and completeness obtainable from the public domain touristic images alone and from the combination with spherical panoramas. We furthermore discuss the challenges of co-registering the weakly connected 3d point cloud fragments resulting from the limited coverage of the touristic photos. We then describe an approach using spherical photogrammetry as a virtual topographic survey allowing the coregistration of a detailed and accurate single 3d model of the temple interior and exterior.
ABSTRACT:For architectural metric documentation, Spherical Photogrammetry (SP) has demonstrated its validity and efficiency in many projects already. The speed of surveying is high, the accuracy and completeness of the plotting are satisfactory. However, there are still many problems to be solved. The weakest point is the orientation procedure, which is rather difficult to perform, in the sense that only very experienced people can run it, and few people only make use of it. The old orientation steps are 1) model formation (limited to binocular panoramas couples); 2) link of all the models in a block adjustment with independent model triangulation; 3) block bundle adjustment with 4 parameters/pano (3 coord.+1 orientation bearing); 4) block bundle adjustment with 6 parameters/pano, say the previous 4 + 2 correction angles around the horizontal axes. The panoramas must be spherical and quasihorizontal. In order to make easier the orientation, enabling more people to use SP, an improved approach has been set up. It consists in the combination of any possible model formed either by three and two panoramas. The trinocular vision, say the combination of three different panoramas to form a unique model, has the advantage to be much more robust in comparison to binocular vision in the sense that the trinocular model is likely to be more error-free than any of the three composing binocular models. It contains less model deformation, the model coordinates are validated by the mutual comparison of the three intersecting binocular models. In addition, the number of possible trinocular models is normally much larger than the one of binocular models. The steps for a semi-automatic orientation of a block of panoramas proceed as follows:Form any possible trinocular models by combination of the panoramas; -in case that no trinocular model has been formed, form any possible binocular model; -run a block adjustment with the algorithm of independent model, to link together the models in a unique reference system; -run a block bundle adjustment with collinearity equations with 4 unknown parameters per panorama; -run a block bundle adjustment with collinearity equations with 6 unknown parameters per panorama. The control requirements are limited to one fixed control point and two perpendicular constraints. Given a project with n panoramas, the trinocular possible models are the combination of n, 3 by 3, say (n*(n-1)*(n-2))/3!. As an example, in a project with 10 panoramas the trinocular possible models are 120, while the possible binocular models are (n*(n-1))/2= 45. Obviously not all the panoramas will be formed, because a minimum of four common tie points is required. It is possible to select and filter out the best models by fixing a critical value on sigma naught for testing. The advantages are as follows:no need of approximate value for the unknown coordinates and parameters; -easiness to find gross errors in the gradual block formation. The epipolar geometry has been investigated, the expression of the curve described and asses...
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