Mobile graphics: SIGGRAPH Asia 2017 course

Peer ReviewedPostprint (published version

Evaluating indoor positioning systems in a shopping mall : the lessons learned from the IPIN 2018 competition

The Indoor Positioning and Indoor Navigation (IPIN) conference holds an annual competition in which indoor localization systems from different research groups worldwide are evaluated empirically. The objective of this competition is to establish a systematic evaluation methodology with rigorous metrics both for real-time (on-site) and post-processing (off-site) situations, in a realistic environment unfamiliar to the prototype developers. For the IPIN 2018 conference, this competition was held on September 22nd, 2018, in Atlantis, a large shopping mall in Nantes (France). Four competition tracks (two on-site and two off-site) were designed. They consisted of several 1 km routes traversing several floors of the mall. Along these paths, 180 points were topographically surveyed with a 10 cm accuracy, to serve as ground truth landmarks, combining theodolite measurements, differential global navigation satellite system (GNSS) and 3D scanner systems. 34 teams effectively competed. The accuracy score corresponds to the third quartile (75th percentile) of an error metric that combines the horizontal positioning error and the floor detection. The best results for the on-site tracks showed an accuracy score of 11.70 m (Track 1) and 5.50 m (Track 2), while the best results for the off-site tracks showed an accuracy score of 0.90 m (Track 3) and 1.30 m (Track 4). These results showed that it is possible to obtain high accuracy indoor positioning solutions in large, realistic environments using wearable light-weight sensors without deploying any beacon. This paper describes the organization work of the tracks, analyzes the methodology used to quantify the results, reviews the lessons learned from the competition and discusses its future

Focus stacking in UAV-based inspection

In UAV-based inspection the most common problems are motion blur and focusing issues. These problems are often due to low-light environment, which can be compensated to some extent with shorter exposure times by using larger apertures and luminous lenses. Large apertures lead to limited depth of field and a solution called focus stacking can be used to extent the focal depth. The main goal of this thesis was to find out the feasibility of focus stacking in UAV inspection and a prototype system was designed and implemented. The acquisition system was implemented with an industrial type camera and an electrical liquid polymer lens. The post-processing software was implemented with OpenCV computer vision library because libraries offer the best possibilities to affect the low-level functionality. Three algorithms were chosen for the image registration and three for the image fusion. In addition, improvements to the speed and accuracy of the registration were examined. The implemented system was compared to equivalent open-source applications in each phase and it outperformed those applications in general performance. The most important goal was achieved and the system managed to improve the image data. A sequential acquisition system is not the best option on moving platform due to the perspective changes causing artifacts in image fusion. Also the optical resolution of the liquid lens was not enough for high resolution inspection imaging. However the idea of focus stacking works and the best solution for a mobile platform would be a multi-sensor system capturing the images simultaneously

Heritage Recording and 3D Modeling with Photogrammetry and 3D Scanning

The importance of landscape and heritage recording and documentation with optical remote sensing sensors is well recognized at international level. The continuous development of new sensors, data capture methodologies and multi-resolution 3D representations, contributes significantly to the digital 3D documentation, mapping, conservation and representation of landscapes and heritages and to the growth of research in this field. This article reviews the actual optical 3D measurement sensors and 3D modeling techniques, with their limitations and potentialities, requirements and specifications. Examples of 3D surveying and modeling of heritage sites and objects are also shown throughout the paper