Using Computer Vision Photogrammetry (Agisoft Photoscan)

USING COMPUTER VISION PHOTOGRAMMETRY (AGISOFT PHOTOSCAN) TO RECORD AND ANALYZE UNDERWATER SHIPWRECK SITES A Dissertation by KOTARO YAMAFUNE Submitted to the Office of Graduate and Professional Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Chair of Committee, Luis Filipe Viera de Castro Committee Members, Kevin J. Crisman Donny Hamilton Tim McLaughlin Head of Department, Cynthia Werner May 2016 Major Subject: Anthropology Copyright 2016 Kotaro Yamafune ABSTRACT In 2010, a new off-the-shelf software for Computer Vision Photogrammetry, Agisoft PhotoScan, became available to nautical archeologists, and this technology has since become a popular method for recording underwater shipwreck sites. Today (2015), there are still active discussions regarding the accuracy and usage of Computer Vision Photogrammetry in the discipline of nautical archaeology. The author believes that creating a 1:1 scale constrained photogrammetric model of a submerged shipwreck site is not difficult as long as archaeologists first establish a local coordinate system of the site. After creation of a 1:1 scale constrained photogrammetric model, any measurements of the site can be obtained from the created 3D model and its digital data. This means that archaeologists never need to revisit the archaeological site to take additional measurements. Thus, Computer Vision Photogrammetry can substantially reduce archaeologists’ working time in water, and maximize quantity and quality of the data acquired. Furthermore, the author believes that the acquired photogrammetric data can be utilized in traditional ship reconstruction and other general studies of shipwrecks. With this idea, the author composed a new methodology that fuses Computer Vision Photogrammetry and other digital tools into traditional research methods of nautical archaeology. Using this method, archaeologists can create 3D models that accurately represent submerged cultural heritage sites, and these can be used as representative archaeological data. These types of representative data include (but are not limited to) ii site plans, technical artifact or timber drawings, shipwreck section profiles, georeferenced archaeological information databases, site-monitoring systems, digital hull fragment models and many other types of usable and practical 3D models. In this dissertation, the author explains his methodology and related new ideas. iii DEDICATION To my father and mother, who always trust and encourage me. Without their support, I could not finish this research. I hereby present this dissertation to my loving parents to be apprised that they are the best father and mother in the world. iv ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Luis Filipe Viera de Castro, who always supported my efforts. Without him, I would have never finished this research. I would also like to recognize the support and important contributions of my committee members, Dr. Kevin J. Crisman, Dr. Donny Hamilton and Dr. Tim McLaughlin. I would like to acknowledge my friends Dr. Rodrigo Torres and Ms. Samila Ferreira. As teammates in the J. Richard Steffy Ship Reconstruction Laboratory, we spent long days and memorable moments together; we were best colleagues, best friends, and they became my family in College Station. They always helped me with my research and my life in America. I also want to give my gratitude to all of my friends in the Nautical Archaeology Program, who always delivered to me new ideas, knowledge, insights, and smiles; especially to Lindsey Thomas and Dave Ruff, who revised my dissertation and helped me with my English all the time without any complaints. In the end, I give my utmost gratitude to my parents, Shigeki Yamafune and Nobuko Yamafune, who have always loved and encouraged me these past 31 years. They are the most loving parents, yet I hope they know that they are the most loved parents as well. v TABLE OF CONTENTS Page ABSTRACT ................................................................................................................... ii DEDICATION ............................................................................................................... iv ACKNOWLEDGEMENTS .......................................................................................... v TABLE OF CONTENTS .............................................................................................. vi LIST OF FIGURES ....................................................................................................... ix LIST OF TABLES......................................................................................................... xvi CHAPTER I INTRODUCTION ................................................................................... 1 Introduction: Objective of This Dissertation ................................... 1 Current Status of Study ...................................................................... 4 Methodology ...................................................................................... 7 II DATA COLLECTION ............................................................................ 8 Photography ....................................................................................... 8 Underwater Coded Targets ............................................................... 20 Recommended Sizes for Coded Targets (Based on Focal Length and Distance) ................................................................. 23 Recommended Flight Plan with Coded Targets ..................... 27 Local Coordinate Network ............................................................... 28 Methodology for Testing Different Local Coordinate Systems ....................................................................................... 31 Trilateration (Direct Survey Method) ...................................... 32 Enclosure .................................................................................... 35 Scale Bars ................................................................................... 37 Total Station .............................................................................. 38 Comparison of the Different Methods...................................... 40 Conclusion: Recommended Survey Method ........................... 42 Data Collection and Database .......................................................... 44 Data Collection .......................................................................... 45 vi CHAPTER Page Database .................................................................................... 48 III DATA PROCESSING............................................................................. 51 Computer Vision Photogrammetry (Agisoft PhotoScan) ............... 51 Align Photos ............................................................................... 53 Build Dense Cloud .................................................................... 57 Build Mesh ................................................................................. 62 Build Texture ............................................................................. 67 Photogrammetric Model of the Saveiro Wooden Ship Model ......................................................................................... 74 Modeling a Sail (Mesh Replacement Techniques) .................. 79 Video Frame Photogrammetry ........................................................ 82 Underwater Video Frame Photogrammetry Using GoPro ...... 89 Georeferenced Orthophotos .............................................................. 94 GIS Based Spatial Data Archive ..................................................... 97 2D Site Plan and Timber Catalog Templates .................................. 100 Erasing Instead of Tracing Method .......................................... 101 Timber Drawing Templates (with Automated Masking) ........ 106 Section Profiles of Shipwreck Sites ................................................. 113 Exporting Photogrammetric Models to Autodesk Maya......... 116 Creating CT Scan Cameras in Maya ........................................ 119 Conclusion: Section Profiles ..................................................... 124 IV DATA ANALYSIS ................................................................................. 125 Data Analysis: Legacy of J. Richard Steffy .................................... 125 Hull Line Reconstruction ............................................................... 125 Mold-and-Batten Model Fairing .............................................. 131 Testing Author’s Hull Line Reconstruction ............................ 133 Archival Research and Shipwreck Analysis ................................. 138 Hull Analysis .................................................................................... 139 Interactive Fragment Model ...................................................... 140 Site Analysis ..................................................................................... 149 Photogrammetry Based Site Monitoring .................................. 150 3D Reconstructions ......................................................................... 153 NURBS Modeling and Polygon Modeling ............................. 154 V PUBLIC OUTREACH & PUBLICATION ........................................... 159 Visual Tour Animation ................................................................... 159 vii CHAPTER Page Interactive Virtual Museum............................................................

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