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Klemen Istenič
Underwater Robotics Research Center (CIRS), Computer Vision and Robotics Institute (VICOROB), University of Girona, Edifici P-IV, Campus de Montilivi, 17071 Girona, Spain

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Journal article
Published: 14 November 2019 in ISPRS Journal of Photogrammetry and Remote Sensing
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Improvements in structure-from-motion techniques are enabling many scientific fields to benefit from the routine creation of detailed 3D models. However, for a large number of applications, only a single camera is available for the image acquisition, due to cost or space constraints in the survey platforms. Monocular structure-from-motion raises the issue of properly estimating the scale of the 3D models, in order to later use those models for metrology. The scale can be determined from the presence of visible objects of known dimensions, or from information on the magnitude of the camera motion provided by other sensors, such as GPS. This paper addresses the problem of accurately scaling 3D models created from monocular cameras in GPS-denied environments, such as in underwater applications. Motivated by the common availability of underwater laser scalers, we present two novel approaches which are suitable for different laser scaler configurations. A fully unconstrained method enables the use of arbitrary laser setups, while a partially constrained method reduces the need for calibration by only assuming parallelism on the laser beams and equidistance with the camera. The proposed methods have several advantages with respect to existing methods. By using the known geometry of the scene represented by the 3D model, along with some parameters of the laser scaler geometry, the need for laser alignment with the optical axis of the camera is eliminated. Furthermore, the extremely error-prone manual identification of image points on the 3D model, currently required in image-scaling methods, is dispensed with. The performance of the methods and their applicability was evaluated both on data generated from a realistic 3D model and on data collected during an oceanographic cruise in 2017. Three separate laser configurations have been tested, encompassing nearly all possible laser setups, to evaluate the effects of terrain roughness, noise, camera perspective angle and camera-scene distance on the final estimates of scale. In the real scenario, the computation of 6 independent model scale estimates using our fully unconstrained approach, produced values with a standard deviation of 0.3%. By comparing the values to the only other possible method currently usable for this dataset, we showed that the consistency of scales obtained for individual lasers is much higher for our approach (0.6% compared to 4%).

ACS Style

Klemen Istenič; Nuno Gracias; Aurélien Arnaubec; Javier Escartín; Rafael Garcia. Automatic scale estimation of structure from motion based 3D models using laser scalers in underwater scenarios. ISPRS Journal of Photogrammetry and Remote Sensing 2019, 159, 13 -25.

AMA Style

Klemen Istenič, Nuno Gracias, Aurélien Arnaubec, Javier Escartín, Rafael Garcia. Automatic scale estimation of structure from motion based 3D models using laser scalers in underwater scenarios. ISPRS Journal of Photogrammetry and Remote Sensing. 2019; 159 ():13-25.

Chicago/Turabian Style

Klemen Istenič; Nuno Gracias; Aurélien Arnaubec; Javier Escartín; Rafael Garcia. 2019. "Automatic scale estimation of structure from motion based 3D models using laser scalers in underwater scenarios." ISPRS Journal of Photogrammetry and Remote Sensing 159, no. : 13-25.

Preprint
Published: 29 October 2019
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Marine and Underwater resources are important part of the economy of many countries. This requires significant financial resources into their construction and maintentance. Robotics is expected to fill this void, by automating and/or removing humans from hostile environments in order to easily perform maintenance tasks. The Robocademy Marie Sklodowska-Curie Initial Training Network was funded by the European Union's FP7 research program in order to train 13 Fellows into world-leading researchers in Marine and Underwater Robotics. The fellows developed guided research into three areas of key importance: Autonomy, Disturbance Rejection, and Perception. This paper presents a summary of the fellows' research in the three action lines. 71 scientific publications were the primary result of this project, with many other publications currently in the pipeline. Most of the fellows have found employment in Europe, which shows the high demand for this kind of experts. We believe the results from this project are already having an impact in the marine robotics industry, as key technologies are being adopted already.

ACS Style

Matias Valdenegro-Toro; Mariela De Lucas Alvarez; Mariia Dmitrieva; Bilal Wehbe; Georgios Salavasidis; Shahab Heshmati-Alamdari; Juan F. Fuentes-Pérez; Veronika Yordanova; Klemen Istenič; Thomas Guerneve. Results from the Robocademy ITN: Autonomy, Disturbance Rejection and Perception for Advanced Marine Robotics. 2019, 1 .

AMA Style

Matias Valdenegro-Toro, Mariela De Lucas Alvarez, Mariia Dmitrieva, Bilal Wehbe, Georgios Salavasidis, Shahab Heshmati-Alamdari, Juan F. Fuentes-Pérez, Veronika Yordanova, Klemen Istenič, Thomas Guerneve. Results from the Robocademy ITN: Autonomy, Disturbance Rejection and Perception for Advanced Marine Robotics. . 2019; ():1.

Chicago/Turabian Style

Matias Valdenegro-Toro; Mariela De Lucas Alvarez; Mariia Dmitrieva; Bilal Wehbe; Georgios Salavasidis; Shahab Heshmati-Alamdari; Juan F. Fuentes-Pérez; Veronika Yordanova; Klemen Istenič; Thomas Guerneve. 2019. "Results from the Robocademy ITN: Autonomy, Disturbance Rejection and Perception for Advanced Marine Robotics." , no. : 1.

Journal article
Published: 07 September 2019 in Remote Sensing
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Rapid developments in the field of underwater photogrammetry have given scientists the ability to produce accurate 3D models which are now increasingly used in the representation and study of local areas of interest. This paper addresses the lack of systematic analysis of 3D reconstruction and navigation fusion strategies, as well as associated error evaluation of models produced at larger scales in GPS-denied environments using a monocular camera (often in deep sea scenarios). Based on our prior work on automatic scale estimation of SfM-based 3D models using laser scalers, an automatic scale accuracy framework is presented. The confidence level for each of the scale error estimates is independently assessed through the propagation of the uncertainties associated with image features and laser spot detections using a Monte Carlo simulation. The number of iterations used in the simulation was validated through the analysis of the final estimate behavior. To facilitate the detection and uncertainty estimation of even greatly attenuated laser beams, an automatic laser spot detection method was developed, with the main novelty of estimating the uncertainties based on the recovered characteristic shapes of laser spots with radially decreasing intensities. The effects of four different reconstruction strategies resulting from the combinations of Incremental/Global SfM, and the a priori and a posteriori use of navigation data were analyzed using two distinct survey scenarios captured during the SUBSAINTES 2017 cruise (doi: 10.17600/17001000). The study demonstrates that surveys with multiple overlaps of nonsequential images result in a nearly identical solution regardless of the strategy (SfM or navigation fusion), while surveys with weakly connected sequentially acquired images are prone to produce broad-scale deformation (doming effect) when navigation is not included in the optimization. Thus the scenarios with complex survey patterns substantially benefit from using multiobjective BA navigation fusion. The errors in models, produced by the most appropriate strategy, were estimated at around 1 % in the central parts and always inferior to 5 % on the extremities. The effects of combining data from multiple surveys were also evaluated. The introduction of additional vectors in the optimization of multisurvey problems successfully accounted for offset changes present in the underwater USBL-based navigation data, and thus minimize the effect of contradicting navigation priors. Our results also illustrate the importance of collecting a multitude of evaluation data at different locations and moments during the survey.

ACS Style

Klemen Istenič; Nuno Gracias; Aurélien Arnaubec; Javier Escartín; Rafael Garcia. Scale Accuracy Evaluation of Image-Based 3D Reconstruction Strategies Using Laser Photogrammetry. Remote Sensing 2019, 11, 2093 .

AMA Style

Klemen Istenič, Nuno Gracias, Aurélien Arnaubec, Javier Escartín, Rafael Garcia. Scale Accuracy Evaluation of Image-Based 3D Reconstruction Strategies Using Laser Photogrammetry. Remote Sensing. 2019; 11 (18):2093.

Chicago/Turabian Style

Klemen Istenič; Nuno Gracias; Aurélien Arnaubec; Javier Escartín; Rafael Garcia. 2019. "Scale Accuracy Evaluation of Image-Based 3D Reconstruction Strategies Using Laser Photogrammetry." Remote Sensing 11, no. 18: 2093.

Research article
Published: 03 June 2019 in Aquatic Conservation: Marine and Freshwater Ecosystems
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In the Mediterranean Sea, gorgonians are among the main habitat‐forming species of benthic communities on the continental shelf and slope, playing an important ecological role in coral gardens. In areas where bottom trawling is restricted, gorgonians represent one of the main components of trammel net bycatch. Since gorgonians are long‐lived and slow‐growing species, impacts derived from fishing activities can have far‐reaching and long‐lasting effects, jeopardizing their long‐term viability. Thus, mitigation and ecological restoration initiatives focusing on gorgonian populations on the continental shelf are necessary to enhance and speed up their natural recovery. Bycatch gorgonians from artisanal fishermen were transplanted into artificial structures, which were then deployed at 85 m depth on the outer continental shelf of the marine protected area of Cap de Creus (north‐west Mediterranean Sea, Spain). After 1 year, high survival rates of transplanted colonies (87.5%) were recorded with a hybrid remotely operated vehicle. This pilot study shows, for the first time, the survival potential of bycatch gorgonians once returned to their habitat on the continental shelf, and suggests the potential success of future scaled‐up restoration activities.

ACS Style

Maria Montseny; Cristina Linares; Núria Viladrich; Alejandro Olariaga; Marc Carreras; Narcís Palomeras; Nuno Gracias; Klemen Istenič; Rafael Garcia; Stefano Ambroso; Andreu Santín; Jordi Grinyó; Josep‐Maria Gili; Andrea Gori. First attempts towards the restoration of gorgonian populations on the Mediterranean continental shelf. Aquatic Conservation: Marine and Freshwater Ecosystems 2019, 29, 1278 -1284.

AMA Style

Maria Montseny, Cristina Linares, Núria Viladrich, Alejandro Olariaga, Marc Carreras, Narcís Palomeras, Nuno Gracias, Klemen Istenič, Rafael Garcia, Stefano Ambroso, Andreu Santín, Jordi Grinyó, Josep‐Maria Gili, Andrea Gori. First attempts towards the restoration of gorgonian populations on the Mediterranean continental shelf. Aquatic Conservation: Marine and Freshwater Ecosystems. 2019; 29 (8):1278-1284.

Chicago/Turabian Style

Maria Montseny; Cristina Linares; Núria Viladrich; Alejandro Olariaga; Marc Carreras; Narcís Palomeras; Nuno Gracias; Klemen Istenič; Rafael Garcia; Stefano Ambroso; Andreu Santín; Jordi Grinyó; Josep‐Maria Gili; Andrea Gori. 2019. "First attempts towards the restoration of gorgonian populations on the Mediterranean continental shelf." Aquatic Conservation: Marine and Freshwater Ecosystems 29, no. 8: 1278-1284.

Journal article
Published: 25 March 2019 in Sensors
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To autonomously explore complex underwater environments, it is convenient to develop motion planning strategies that do not depend on prior information. In this publication, we present a robotic exploration algorithm for autonomous underwater vehicles (AUVs) that is able to guide the robot so that it explores an unknown 2-dimensional (2D) environment. The algorithm is built upon view planning (VP) and frontier-based (FB) strategies. Traditional robotic exploration algorithms seek full coverage of the scene with data from only one sensor. If data coverage is required for multiple sensors, multiple exploration missions are required. Our approach has been designed to sense the environment achieving full coverage with data from two sensors in a single exploration mission: occupancy data from the profiling sonar, from which the shape of the environment is perceived, and optical data from the camera, to capture the details of the environment. This saves time and mission costs. The algorithm has been designed to be computationally efficient, so that it can run online in the AUV's onboard computer. In our approach, the environment is represented using a labeled quadtree occupancy map which, at the same time, is used to generate the viewpoints that guide the exploration. We have tested the algorithm in different environments through numerous experiments, which include sea operations using the Sparus II AUV and its sensor suite.

ACS Style

Eduard Vidal; Narcís Palomeras; Klemen Istenič; Juan David Hernández; Marc Carreras. Two-Dimensional Frontier-Based Viewpoint Generation for Exploring and Mapping Underwater Environments. Sensors 2019, 19, 1460 .

AMA Style

Eduard Vidal, Narcís Palomeras, Klemen Istenič, Juan David Hernández, Marc Carreras. Two-Dimensional Frontier-Based Viewpoint Generation for Exploring and Mapping Underwater Environments. Sensors. 2019; 19 (6):1460.

Chicago/Turabian Style

Eduard Vidal; Narcís Palomeras; Klemen Istenič; Juan David Hernández; Marc Carreras. 2019. "Two-Dimensional Frontier-Based Viewpoint Generation for Exploring and Mapping Underwater Environments." Sensors 19, no. 6: 1460.

Conference paper
Published: 01 May 2018 in 2018 IEEE International Conference on Robotics and Automation (ICRA)
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Achieving full autonomous robotic environment exploration in the underwater domain is very challenging, mainly due to noisy acoustic sensors, high localization error, control disturbances of the water and lack of accurate underwater maps. In this work we present a robotic exploration algorithm for underwater vehicles that does not rely on prior information about the environment. Our method has been greatly influenced by many robotic exploration, view planning and path planning algorithms. The proposed method constitutes a significant improvement over our previous work [1]: Firstly, we refine our exploration approach to improve robustness; Secondly, we propose an alternative map representation based on the quadtree data structure that allows different relevant queries to be performed efficiently, reducing the computational cost of the viewpoint generation process; Thirdly, we present an algorithm that is capable of generating consistent maps even when noisy sonar data is used. The aforementioned contributions have increased the reliability of the algorithm, allowing new real experiments performed in artificial structures but also in more challenging natural environments, from which we provide a 3D reconstruction to show that with this algorithm full optical coverage is obtained.

ACS Style

Eduard Vidal; Juan David Hernandez; Klemen Istenic; Marc Carreras. Optimized Environment Exploration for Autonomous Underwater Vehicles. 2018 IEEE International Conference on Robotics and Automation (ICRA) 2018, 6409 -6416.

AMA Style

Eduard Vidal, Juan David Hernandez, Klemen Istenic, Marc Carreras. Optimized Environment Exploration for Autonomous Underwater Vehicles. 2018 IEEE International Conference on Robotics and Automation (ICRA). 2018; ():6409-6416.

Chicago/Turabian Style

Eduard Vidal; Juan David Hernandez; Klemen Istenic; Marc Carreras. 2018. "Optimized Environment Exploration for Autonomous Underwater Vehicles." 2018 IEEE International Conference on Robotics and Automation (ICRA) , no. : 6409-6416.

Proceedings article
Published: 01 June 2017 in OCEANS 2017 - Aberdeen
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Accurate and detailed 3-dimensional (3D) models of the underwater environment are becoming increasingly important in modern marine surveys, since they convey immense information that can be easily interpreted. Techniques such as bundle adjustment (BA) and structure from motion (SfM), which jointly estimate sparse 3D points of the scene and camera poses, have gained popularity in underwater mapping applications. However, for large-area surveys these methods are computationally expensive and not intended for online application. This paper proposes an SfM pipeline based on solving the BA problem in an incremental and efficient way. Furthermore, the new system can provide not only the solution of the optimization (camera trajectory along time and the 3D points of the environment), but also the estimate of the uncertainty associated with the 3D reconstruction. This system is able to produce results in mission-time, i.e. while the robot is in the water or very shortly afterwards. Such quick availability is of great importance during survey operations as it allows data quality assessment in-situ, and eventual replanning of missions in case of need.

ACS Style

Klemen Istenic; Viorela Ila; Lukas Polok; Nuno Gracias; Rafael Garcia. Mission-time 3D reconstruction with quality estimation. OCEANS 2017 - Aberdeen 2017, 1 -9.

AMA Style

Klemen Istenic, Viorela Ila, Lukas Polok, Nuno Gracias, Rafael Garcia. Mission-time 3D reconstruction with quality estimation. OCEANS 2017 - Aberdeen. 2017; ():1-9.

Chicago/Turabian Style

Klemen Istenic; Viorela Ila; Lukas Polok; Nuno Gracias; Rafael Garcia. 2017. "Mission-time 3D reconstruction with quality estimation." OCEANS 2017 - Aberdeen , no. : 1-9.

Journal article
Published: 17 February 2017 in IEEE Robotics and Automation Letters
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In this paper, we propose a method to automate the exploration of unknown underwater structures for autonomous underwater vehicles (AUVs). The proposed algorithm iteratively incorporates exteroceptive sensor data and replans the next-best-view (NBV) in order to fully map an underwater structure. This approach does not require prior environment information. However, a safe exploration depth and the exploration area (defined by a bounding box, parametrized by its size, location and resolution) must be provided by the user. The algorithm operates online by iteratively conducting the following three tasks: 1) Profiling sonar data is firstly incorporated into a 2- dimensional (2D) grid map, where voxels are labeled according to their state (a voxel can be labeled as empty, unseen, occluded, occplane, occupied or viewed). 2) Useful viewpoints to continue exploration are generated according to the map. 3) A safe path is generated to guide the robot towards the next viewpoint location. Two sensors are used in this approach: a scanning profiling sonar, which is used to build an occupancy map of the surroundings, and an optical camera, which acquires optical data of the scene. Finally, in order to demonstrate the feasibility of our approach we provide real-world results using the Sparus II AUV.

ACS Style

Eduard Vidal; Juan David Hernandez; Klemen Istenic; Marc Carreras. Online View Planning for Inspecting Unexplored Underwater Structures. IEEE Robotics and Automation Letters 2017, 2, 1436 -1443.

AMA Style

Eduard Vidal, Juan David Hernandez, Klemen Istenic, Marc Carreras. Online View Planning for Inspecting Unexplored Underwater Structures. IEEE Robotics and Automation Letters. 2017; 2 (3):1436-1443.

Chicago/Turabian Style

Eduard Vidal; Juan David Hernandez; Klemen Istenic; Marc Carreras. 2017. "Online View Planning for Inspecting Unexplored Underwater Structures." IEEE Robotics and Automation Letters 2, no. 3: 1436-1443.

Journal article
Published: 26 July 2016 in Sensors
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We present an approach for navigating in unknown environments while, simultaneously, gathering information for inspecting underwater structures using an autonomous underwater vehicle (AUV). To accomplish this, we first use our pipeline for mapping and planning collision-free paths online, which endows an AUV with the capability to autonomously acquire optical data in close proximity. With that information, we then propose a reconstruction pipeline to create a photo-realistic textured 3D model of the inspected area. These 3D models are also of particular interest to other fields of study in marine sciences, since they can serve as base maps for environmental monitoring, thus allowing change detection of biological communities and their environment over time. Finally, we evaluate our approach using the Sparus II, a torpedo-shaped AUV, conducting inspection missions in a challenging, real-world and natural scenario.

ACS Style

Juan David Hernández; Klemen Istenič; Nuno Ricardo Estrela Grácias; Narcís Palomeras; Rafael García Campos; Eduard Vidal; Eduard Vidal Garcia; Marc Carreras. Autonomous Underwater Navigation and Optical Mapping in Unknown Natural Environments. Sensors 2016, 16, 1174 .

AMA Style

Juan David Hernández, Klemen Istenič, Nuno Ricardo Estrela Grácias, Narcís Palomeras, Rafael García Campos, Eduard Vidal, Eduard Vidal Garcia, Marc Carreras. Autonomous Underwater Navigation and Optical Mapping in Unknown Natural Environments. Sensors. 2016; 16 (8):1174.

Chicago/Turabian Style

Juan David Hernández; Klemen Istenič; Nuno Ricardo Estrela Grácias; Narcís Palomeras; Rafael García Campos; Eduard Vidal; Eduard Vidal Garcia; Marc Carreras. 2016. "Autonomous Underwater Navigation and Optical Mapping in Unknown Natural Environments." Sensors 16, no. 8: 1174.

Journal article
Published: 25 March 2016 in Sensors
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This paper presents a new tracking system for autonomous underwater vehicles (AUVs) navigating in a close formation, based on computer vision and the use of active light markers. While acoustic localization can be very effective from medium to long distances, it is not so advantageous in short distances when the safety of the vehicles requires higher accuracy and update rates. The proposed system allows the estimation of the pose of a target vehicle at short ranges, with high accuracy and execution speed. To extend the field of view, an omnidirectional camera is used. This camera provides a full coverage of the lower hemisphere and enables the concurrent tracking of multiple vehicles in different positions. The system was evaluated in real sea conditions by tracking vehicles in mapping missions, where it demonstrated robust operation during extended periods of time.

ACS Style

Josep Bosch; Nuno Gracias; Pere Ridao; Klemen Istenič; David Ribas. Close-Range Tracking of Underwater Vehicles Using Light Beacons. Sensors 2016, 16, 429 .

AMA Style

Josep Bosch, Nuno Gracias, Pere Ridao, Klemen Istenič, David Ribas. Close-Range Tracking of Underwater Vehicles Using Light Beacons. Sensors. 2016; 16 (4):429.

Chicago/Turabian Style

Josep Bosch; Nuno Gracias; Pere Ridao; Klemen Istenič; David Ribas. 2016. "Close-Range Tracking of Underwater Vehicles Using Light Beacons." Sensors 16, no. 4: 429.

Book chapter
Published: 28 November 2015 in Advances in Intelligent Systems and Computing
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We present an approach for navigating in unknown environments, while gathering information for inspecting underwater structures using an autonomous underwater vehicle (AUV). To accomplish this, we first use our framework for mapping and planning collision-free paths online, which endows an AUV with the capability to autonomously acquire optical data in close proximity. With that information, we then propose a reconstruction framework to create a 3-dimensional (3D) geo-referenced photo-mosaic of the inspected area. These 3D mosaics are also of particular interest to other fields of study in marine sciences, since they can serve as base maps for environmental monitoring, thus allowing change detection of biological communities and their environment in the temporal scale. Finally, we evaluate our frameworks, independently, using the SPARUS-II, a torpedo-shaped AUV, conducting missions in real-world scenarios. We also assess our approach in a virtual environment that emulates a natural underwater milieu that requires the aforementioned capabilities.

ACS Style

Juan David Hernández; Klemen Istenic; Nuno Gracias; Rafael García; Pere Ridao; Marc Carreras. Autonomous Seabed Inspection for Environmental Monitoring. Advances in Intelligent Systems and Computing 2015, 27 -39.

AMA Style

Juan David Hernández, Klemen Istenic, Nuno Gracias, Rafael García, Pere Ridao, Marc Carreras. Autonomous Seabed Inspection for Environmental Monitoring. Advances in Intelligent Systems and Computing. 2015; ():27-39.

Chicago/Turabian Style

Juan David Hernández; Klemen Istenic; Nuno Gracias; Rafael García; Pere Ridao; Marc Carreras. 2015. "Autonomous Seabed Inspection for Environmental Monitoring." Advances in Intelligent Systems and Computing , no. : 27-39.

Conference paper
Published: 30 April 2015 in Quality Control by Artificial Vision
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ACS Style

Oksana Hagen; Klemen Istenič; Vibhav Bharti; Maruf A. Dhali; Daniel Barmaimon; Jeremie Houssineau; Daniel Clark. Calibration of asynchronous smart phone cameras from moving objects. Quality Control by Artificial Vision 2015, 1 .

AMA Style

Oksana Hagen, Klemen Istenič, Vibhav Bharti, Maruf A. Dhali, Daniel Barmaimon, Jeremie Houssineau, Daniel Clark. Calibration of asynchronous smart phone cameras from moving objects. Quality Control by Artificial Vision. 2015; ():1.

Chicago/Turabian Style

Oksana Hagen; Klemen Istenič; Vibhav Bharti; Maruf A. Dhali; Daniel Barmaimon; Jeremie Houssineau; Daniel Clark. 2015. "Calibration of asynchronous smart phone cameras from moving objects." Quality Control by Artificial Vision , no. : 1.