Experiments on Surface Reconstruction for Partially Submerged Marine Structures

Over the past 10 years, significant scientific effort has been dedicated to the problem of three-dimensional (3-D) surface reconstruction for structural systems. However, the critical area of marine structures remains insufficiently studied. The research presented here focuses on the problem of 3-D surface reconstruction in the marine environment. This paper summarizes our hardware, software, and experimental contributions on surface reconstruction over the past few years (2008–2011). We propose the use of off-the-shelf sensors and a robotic platform to scan marine structures both above and below the waterline, and we develop a method and software system that uses the Ball Pivoting Algorithm (BPA) and the Poisson reconstruction algorithm to reconstruct 3-D surface models of marine structures from the scanned data. We have tested our hardware and software systems extensively in Singapore waters, including operating in rough waters, where water currents are around 1–2 m/s. We present results on construction of various 3-D models of marine structures, including slowly moving structures such as floating platforms, moving boats, and stationary jetties. Furthermore, the proposed surface reconstruction algorithm makes no use of any navigation sensor such as GPS, a Doppler velocity log, or an inertial navigation system.Singapore-MIT Alliance for Research and Technology. Center for Environmental Sensing and Modelin

3D GEOSPATIAL INDOOR NAVIGATION FOR DISASTER RISK REDUCTION AND RESPONSE IN URBAN ENVIRONMENT

Disaster management for urban environments with complex structures requires 3D extensions of indoor applications to support better risk reduction and response strategies. The paper highlights the need for assessment and explores the role of 3D geospatial information and modeling regarding the indoor structure and navigational routes which can be utilized as disaster risk reduction and response strategy. The reviewed models or methods are analysed testing parameters in the context of indoor risk and disaster management. These parameters are level of detail, connection to outdoor, spatial model and network, handling constraints. 3D reconstruction of indoors requires the structural data to be collected in a feasible manner with sufficient details. Defining the indoor space along with obstacles is important for navigation. Readily available technologies embedded in smartphones allow development of mobile applications for data collection, visualization and navigation enabling access by masses at low cost. The paper concludes with recommendations for 3D modeling, navigation and visualization of data using readily available smartphone technologies, drones as well as advanced robotics for Disaster Management

Coordinated Landing and Mapping with Aerial and Ground Vehicle Teams

Micro Umanned Aerial Vehicle~(UAV) and Umanned Ground Vehicle~(UGV) teams present tremendous opportunities in expanding the range of operations for these vehicles. An effective coordination of these vehicles can take advantage of the strengths of both, while mediate each other's weaknesses. In particular, a micro UAV typically has limited flight time due to its weak payload capacity. To take advantage of the mobility and sensor coverage of a micro UAV in long range, long duration surveillance mission, a UGV can act as a mobile station for recharging or battery swap, and the ability to perform autonomous docking is a prerequisite for such operations. This work presents an approach to coordinate an autonomous docking between a quadrotor UAV and a skid-steered UGV. A joint controller is designed to eliminate the relative position error between the vehicles. The controller is validated in simulations and successful landing is achieved in indoor environment, as well as outdoor settings with standard sensors and real disturbances. Another goal for this work is to improve the autonomy of UAV-UGV teams in positioning denied environments, a very common scenarios for many robotics applications. In such environments, Simultaneous Mapping and Localization~(SLAM) capability is the foundation for all autonomous operations. A successful SLAM algorithm generates maps for path planning and object recognition, while providing localization information for position tracking. This work proposes an SLAM algorithm that is capable of generating high fidelity surface model of the surrounding, while accurately estimating the camera pose in real-time. This algorithm improves on a clear deficiency of its predecessor in its ability to perform dense reconstruction without strict volume limitation, enabling practical deployment of this algorithm on robotic systems

Merging Unmanned Aerial System and Laser Scanning techniques for high resolution 3D modelling of Koutouki Cave, Attica

Η επιστήμη της τηλεανίχνευσης και η τεχνολογία σάρωσης αναγλύφου με λέιζερ μας έδωσαν την ευκαιρία να μελετήσουμε κλειστούς χώρους και περιβάλλοντα όπως τα σπήλαια με τη σύνθετη και μοναδική μορφολογία τους. Στόχος της παρούσας μεταπτυχιακής διατριβής είναι η δημιουργία ενός ολοκληρωμένου τρισδιάστατου μοντέλου του σπηλαίου Κουτούκι στην Παιανία, η ποσοτική ανάλυση των γεωμορφών που συνθέτουν το σπήλαιο και το πάχος των υπερκειμένων στρωμάτων πάνω από το σπήλαιο. Χρησιμοποιήσαμε ένα laser scanner χειρός για την απόκτηση 80.000.000 σημείων με πραγματικές συντεταγμένες (X, Y, Z) για την αποτύπωση ολόκληρου του σπηλαίου συμπεριλαμβανομένων των μικρότερων διαδρομών και των σκοτεινών τμημάτων. Το νέφος σημείων αποτελείται από το δάπεδο, τα τοιχώματα και την οροφή του σπηλαίου, καθώς και τους σταλακτίτες, τους σταλαγμίτες και τις κολόνες που αποτελούν τη διακόσμηση του σπηλαίου. Η απόλυτη και ακριβής τοποθέτηση του νέφους σημείων μέσα σε ένα σύστημα αναφοράς μας δίνει την ευκαιρία για τρισδιάστατες μετρήσεις και την λεπτομερή απεικόνιση των γεωμορφών. Δημιουργώντας το ψηφιακό μοντέλο αναγλύφου του δαπέδου του σπηλαίου, εντοπίσαμε 55 κολόνες όπου με στατιστική ανάλυση μπορέσαμε να τις συσχετίσουμε με το πλαίσιο της ανάπτυξης του σπηλαίου. Οι παράμετροι που προκύπτουν είναι οι ισοϋψείς του σπηλαίου, το ύψος, η γεωμετρία και ο όγκος της κάθε κολόνας, καθώς και ο όγκος της κοιλότητας του ανοιχτού χώρου. Επιπλέον, με τη χρήση μη επανδρωμένου αεροσκάφους και εφαρμόζοντας μια μεθοδολογία βασισμένη στη φωτογραμμετρική επεξεργασία των δεδομένων εικόνας, πραγματοποιήθηκε η σάρωση του αναγλύφου πάνω από το σπήλαιο που μας οδήγησε στην παραγωγή ενός ψηφιακού μοντέλου αναγλύφου του πρανούς. Το τελικό προϊόν είναι ένα επίπεδο πληροφορίας υψηλής ανάλυσης με τις μετρήσεις του πάχους των υπερκειμένων στρωμάτων του σπηλαίου καθώς και τις τοπογραφίας με υψηλή ακρίβεια. Υποστηρίζουμε ότι, με την αποδεδειγμένη μεθοδολογία, είναι δυνατόν να εντοπίσουμε με μεγάλη λεπτομέρεια και ακρίβεια τα γεωμορφολογικά χαρακτηριστικά ενός σπηλαίου, να κάνουμε εκτιμήσεις για τη σπηλαιογένεση ενός σπηλαίου και να παρακολουθήσουμε την εξέλιξη ενός καρστικού συστήματος.Remote sensing techniques and laser scanning technology have given us the opportunity to study indoor environments such as caves with their complex and unique morphology. The objective of this Msc thesis is the generation of a complete 3D model of the Koutouki Cave in Peania, Greece, the quantification analysis of the subsurface structures that consists the cave, and the thickness of the bedding between the cave and the surface. We used a handheld laser scanner for acquiring 80,000,000 points with projected coordinate information (X, Y, Z) covering the entire show cave of Koutouki, including its hidden passages and dark corners. The point cloud covers the floor, the walls and the roof of the cave, as well as the stalactites, stalagmites and the connected columns that constitute the decoration of the cave. The absolute and exact placement of the point cloud within a geographic reference frame gives us the opportunity for three-dimensional measurements and detailed visualization of the subsurface structures. Using open - source software, we managed to make a quantification analysis of the terrain and generate morphological and geometric features of the speleothems. We identified 55 columns by using digital terrain analysis and processed them statistically in order to correlate them to the frame of the cave development. The parameters that derived are the contours, each column height, the speleothem geometry and volume, as well as the volume of the open space cavity. Furthermore, we applied a methodology based on photogrammetric processing of Unmanned Aerial System image data which led us to the production of a digital terrain model of the open-air surface above the cave. The final product is a high-resolution information layer with measurements of the rock thickness between the roof of the underground karstic structure and the open-surface topography with high accuracy. We argue that, by the demonstrated methodology, it is possible to identify with high accuracy and detail the geomorphological features of a cave, estimate the speleogenesis and monitor the evolution of a karstic system