Determining image distortion and PBS (point of best symmetry) in digital images using straight line matrices

[EN] It is impossible to take accurate measurements in photogrammetry without first removing the distortion in images. This paper presents a methodology for correcting radial and tangential distortion and for determining the PBS (Point of Best Symmetry) without knowledge of the interior orientation parameters (IOPs). An analytical plumb-line calibration method is used, measuring only the coordinates of points on straight lines, regardless of the position and direction of these lines within the image. Points belonging to multiple lines can also be used since the effects on their X and Y coordinates are calculated independently. The results obtained on an image of a common scene, taken with a handheld non-metric camera, show a high degree of accuracy even with a minimum number of observables. And its application on a calibrated grid for engineering purposes with a semi-metric camera, results optimal even using a single image. (C) 2016 Elsevier Ltd. All rights reserved.The authors wish to thank CITES Espana and Direccion General de Bienes Culturales y Ensenanzas Artisticas, de la Consejeria de Educacion, Cultura y Universidades de la Comunidad Autonoma de la Region de Murcia, Museo Nacional de Arqueologia Subacuatica. Financial support is gratefully acknowledged from Spanish "I + D + I MINECO" projects CTQ2011-28079-CO3-01 and 02 and CTQ2014-53736-C3-1-P supported by ERDEF funds. The authors also wish to thank Mr. Manuel Planes and Dr. Jose Luis Moya, technical supervisors of the Electron Microscopy Service of the Universitat Politecnica de Valencia.Herráez Boquera, J.; Denia Ríos, JL.; Navarro Esteve, PJ.; Rodríguez Pereña, J.; Martín Sánchez, MT. (2016). Determining image distortion and PBS (point of best symmetry) in digital images using straight line matrices. Measurement. 91:641-650. https://doi.org/10.1016/j.measurement.2016.05.051S6416509

Restoration of paintings on domes with non-developable geometry (Los Santos Juanes Church in Valencia)

[EN] The restoration of paintings on elements in cultural heritage buildings (fundamentally, churches) involves two structural problems: capturing the geometry of the construction element and its development. In many cases, the geometries are regular (e.g., cylinders, spheres, elliptical domes). However, there are cases in which the elements cannot be adapted to any known geometry, much less one that can be mathematically developed. The development of surfaces becomes essential for the restoration of paintings over "flat elements" (over which work is performed on the ground) that are subsequently transferred to the real surface (ceilings). The mathematical transformations that allow regular geometries to be developed are widely known (cartographic projections). However, when the geometry is irregular, there is no development. This study presents a new methodology based on differential rectification and its application for the development of oculi in the Los Santos Juanes Church (Valencia), whose geometry is completely irregular both in shape and as a result of construction defects (and damage caused by fire). The present study focuses on the restoration of paintings damaged by fire.Navarro Esteve, PJ.; Yudici Oliver, SA.; Herráez Boquera, J.; Denia Rios, JL.; Martín Sánchez, MT.; Rodríguez Pereña, J. (2018). Restoration of paintings on domes with non-developable geometry (Los Santos Juanes Church in Valencia). International Journal of Architectural Heritage. 12(2):169-177. https://doi.org/10.1080/15583058.2017.1356946S16917712

Cultural Heritage Restoration of a Hemispherical Vault by 3D Modelling and Projection of Video Images with Unknown Parameters and from Unknown Locations

[EN] Reverse engineering applied to architectural restoration for the reconstruction of structural surfaces depends on metric precision. Sometimes there are elements on these surfaces whose value is even higher than the building itself. This is the case for many churches whose ceilings have pictorial works of art. Reconstruction requires the existence of some identifiable remainder and/or a surface geometry that enables mathematical development. In our case, the vault has an irregular hemispherical geometry (without possible mathematical development), and there are no significant remains of the painting (which was destroyed by a fire). Through the 3D modelling of the irregular vault and two historic frames with a camera of unknown geometry, an inverse methodology is designed to project the original painting without metric deformations. For this, a new methodology to locate the camera positions is developed. After, a 3D virtual mathematical model of the complete image on the vault is calculated, and from it, partial 3D virtual images are automatically calculated depending on the variable unknown positions of the video cannons (distributed along the upper corridor of the apse) that will project them (visually forming a perfect complete 3D image)Herráez Boquera, J.; Denia Rios, JL.; Priego De Los Santos, E.; Navarro Esteve, PJ.; Martín Sánchez, MT.; Rodríguez Pereña, J. (2021). Cultural Heritage Restoration of a Hemispherical Vault by 3D Modelling and Projection of Video Images with Unknown Parameters and from Unknown Locations. Applied Sciences. 11(12):1-12. https://doi.org/10.3390/app11125323112111

Epipolar image rectification through geometric algorithms with unknown parameters

Herráez Boquera, J., Denia Rios, J.L., Navarro Esteve, P.J., Rodríguez Pereña, J., Martín Sánchez M.T."Epipolar image rectification through geometric algorithms with unknown parameters". JJ. Electron. Imaging. 22(4), 043021 (Dec 02, 2013). © (2013) Society of Photo-Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. http://dx.doi.org/10.1117/1.JEI.22.4.043021Image processing in photogrammetry is commonly used for scene reconstruction. Although two-dimensional applications can be solved using isolated images, reconstruction of three-dimensional scenes usually requires the use of multiple images simultaneously. Epipolar image rectification is a common technique for this purpose. It typically requires internal orientation parameters and, therefore, knowledge of camera calibration and relative orientation parameters between images. A reparameterization of the fundamental matrix through a completely geometric algorithm of seven parameters that enables the epipolar image rectification of a photogrammetric stereo pair without introducing any orientation parameters and without premarking ground control points is presented. The algorithm enables the generation of different stereoscopic models with a single photogrammetric pair from unknown cameras, scanned from a book, or frames from video sequences. Stereoscopic models with no parallaxes have been obtained with a standard deviation of <0.5 pixels. (C) 2013 SPIE and IS&THerráez Boquera, J.; Denia Rios, JL.; Navarro Esteve, PJ.; Rodríguez Pereña, J.; Martín Sánchez, MT. (2013). Epipolar image rectification through geometric algorithms with unknown parameters. Journal of Electronic Imaging. 22(4). doi:10.1117/1.JEI.22.4.04302104302122

Modelo de evaluación de la efectividad, continuidad y conectividad del sistema de áreas protegidas costeras mediante el análisis de su flora y vegetación

[ES] Los ecosistemas litorales están fuertemente amenazados por el aumento del nivel del mar, las inundaciones y la litoralización de la población. Aunque se ha intensificado el esfuerzo por declarar áreas protegidas costeras, estas quedan fragmentadas en teselas circundadas por territorios artificalizados. La conectividad entre estas áreas protegidas es por tanto la garantía de la continuidad de los servicios ecosistémicos que proveen. Se propone un modelo para la evaluación de la eficacia potencial del sistema continuo de las áreas protegidas costeras en base al conocimiento de su flora y vegetación. El grado de efectividad pretende ser un indicador para la adopción de medidas de planificación territorial conducentes al fortalecimiento de la red como medida de salvaguarda de la biodiversidad. Para probar el modelo propuesto se ha elegido la costa de Andalucía (S de España), territorio bañado por el Mediterráneo y el Atlántico, susceptible de importantes impactos. Este segmento de costa ha sido sometido durante los últimos 60 años a fuertes presiones de origen antrópico.que han fragmentado y alterado la estructura, composición y funcionalidad de los ecosistemas litorales. Todo ello pone en riesgo tanto los valores que sirvieron para la declaración de un status de protección como la conectividad entre ecosistemas que garanticen la persistencia de sus servicios ecosistémicos. La metodología propuesta para medir la eficacia potencial del sistema se sustenta en el grado de protección legal, el valor fitocenótico y el grado de artificialización. A partir de la integración de los valores obtenidos se ha calculado la consistencia de los nodos y en definitiva la efectividad en red. La aplicación de este método pone de relevancia cuales son las áreas protegidas más vulnerables ante las deficiencias de la red, en especial por las dificultades de conectividad.[EN] Coastal ecosystems are strongly threatened by rising sea levels, flooding and coastalization of the population. Although the increasing effort to protect coastal areas, these are fragmented into tesserae surrounded by artificialized territories. Connectivity between these protected areas is the guarantee of the continuity of the ecosystem services they provide. We proposed a model for the evaluation of the potential effectiveness of the continuous system of coastal protected areas based on knowledge of their flora and vegetation. The degree of effectiveness is intended as an indicator for the adoption of spatial planning measures leading to the strengthening of the network as a measure to safeguard biodiversity. To test the proposed model, the coast of Andalusia (S of Spain) was chosen, a territory bathed by the Mediterranean and the Atlantic, which is susceptible to significant impacts. This coast has been subjected, during the last 60 years, to strong anthropic pressure that have fragmented and altered the structure, composition and functionality of the coastal ecosystems. These impacts threaten the standards in which the protected areas were declared, also jeopardize the connectivity between ecosystems. Consequently, this pressure has negative effects in the ecosystem services development. The methodology we proposed to measure the potential effectiveness of the system is based on the degree of legal protection, the phytogenic value and the degree of artificialisation. Based on the integration of the values obtained, the consistency of the nodes had been calculated and, in short, the effectiveness of the network. The application of this approach highlights which protected areas are most vulnerable to network deficiencies, especially due to connectivity difficulties.Peer reviewe

3D modeling by means of videogrammetry and laser scanners for reverse engineering

[EN] The knowledge of the 3D geometry for reverse engineering studies is based on images and/or distances. The use of scanner laser has replaced the photogrammetry in the last decade, due to its easy handling and intensive data provided. However it requires multiple data captures, a subsequent filtering and a complex data processing, and its accuracy is highly dependent on the material. These limitations mean that many times it will not be the best option (in addition to its high cost). The videogrammetry is capable of generating a high number of images (which implies a high number of points) in a shorter time and regardless of the type of material. This paper analyses the accuracy of a new videogrammetric system respect to two scanner lasers. Results obtained certify that videogrammetry reaches similar accuracy than EScan (high resolution portable 3D scanner for reverse engineering), and higher accuracy than architectural scanner laser. In both cases the time spent in the 3D model generation by means of videogrammetry results much lower and the process is completely automatic requiring no post-processing or filtering work. Finally videogrammetry also enables real 3D object visualization through anaglyphs in all desired positions, while laser systems cannot provide that kind of information. (C) 2016 Elsevier Ltd. All rights reserved.Herráez Boquera, J.; Martínez Llario, JC.; Coll-Aliaga, E.; Martín Sánchez, MT.; Rodríguez Pereña, J. (2016). 3D modeling by means of videogrammetry and laser scanners for reverse engineering. Measurement. 87:216-227. https://doi.org/10.1016/j.measurement.2016.03.005S2162278

Modeling the thickness of vaults in the church of Santa María de Magdalena (Valencia, Spain) with laser scanning techniques

Restoring cultural heritage is an extremely important job due to its immeasurable value. However, it also requires even greater attention in the case of a building. The actions taken on these constructions not only guarantee their preservation from the point of view of their historical value, but they also guarantee their stability as structures. The need to control historic buildings, analyzing their defects and their possible consequences, is decisive in preventing significant damage. This work demonstrates calculating the thickness of vaults in a church. It is easy to determine the interior and exterior 3D geometry of the church using scanner laser techniques. By combining both geometries, it is easy to determine the difference between the interior vaults and the roof of the church. However, the interior of both geometries is completely unknown, and it is not possible to act on their condition for structural consolidation purposes. This work shows the methods used to determine the interior sections of the vault thicknesses by referencing the internal geometry of both models with the interior of the church, using plumb line system scanning. The results obtained show accuracy better than 6 millimeters. © 2013 Elsevier Masson SAS. All rights reserved.Herráez Boquera, J.; Navarro Esteve, PJ.; Denia Rios, JL.; Martín Sánchez, MT.; Rodríguez Pereña, J. (2013). Modeling the thickness of vaults in the church of Santa María de Magdalena (Valencia, Spain) with laser scanning techniques. Journal of Cultural Heritage. doi:10.1016/j.culher.2013.11.015