Integration of Digital Photogrammetry and Terrestrial Laser Scanning for Cultural Heritage Data Recording A thesis accepted by the Faculty of Aerospace Engineering and Geodesy of the University of Stuttgart in partial fulfilment of the requirements for the degree of Doctor of Engineering Sciences (Dr.-Ing.) by Wassim Moussa born in Hama, Syria Committee chair: Prof. Dr.-Ing. habil. Dieter Fritsch Committee member: Prof. Dr.-Ing. habil. Volker Schwieger Date of defence: 28 February 2014 Institute for Photogrammetry University of Stuttgart 2014 Online veröffentlicht unter http://dgk.badw.de/index.php?id=12 und http://elib.uni-stuttgart.de/opus/doku/e-diss.php Contents 3 Contents Contents ................................................................................................................................................ 3 Abstract .................................................................................................................................................. 8 Zusammenfassung ............................................................................................................................ 10 1 Introduction ..................................................................................................................................... 13 1.1 Motivation ................................................................................................................................. 13 1.2 Objectives ................................................................................................................................... 15 1.3 Thesis Outline ........................................................................................................................... 17 2 Generation of 3D Models - An Overview .................................................................................. 18 2.1 Data Acquisition and Geometric Reconstruction ................................................................ 18 2.1.1 Image-Based Approach .................................................................................................... 18 2.1.1.1 Image Acquisition ...................................................................................................... 19 2.1.1.2 Camera Orientation .................................................................................................... 20 2.1.1.3 Surface Points Recovering ......................................................................................... 22 2.1.2 Range-Based Approach .................................................................................................... 26 2.1.2.1 TLS Systems................................................................................................................. 27 2.1.2.2 Range Data Acquisition ............................................................................................. 34 2.1.2.3 Scan Registration ........................................................................................................ 35 2.1.3 Sensor Integration.............................................................................................................. 37 2.1.4 Georeferencing ................................................................................................................... 38 2.2 Surface Reconstruction ............................................................................................................ 38 2.3 Texture Mapping and Visualization ...................................................................................... 39 3 Building Reflectance and RGB Images ...................................................................................... 42 3.1 Imaging Laser Scanner Polar Coordinates ............................................................................ 42 3.2 Central Projection of Laser Scanner Cartesian Coordinates ............................................... 43 3.2.1 Defining 3D Virtual Camera Coordinate System .......................................................... 46 3.2.2 Improving Radiometry and Geometry ........................................................................... 48 3.2.3 Improving Keypoint Localization ................................................................................... 50 4 Contents 4 General Strategy for Digital Images and Laser Scanner Data Integration .......................... 51 4.1 Data Integration Using Accurate Space Resection Methods .............................................. 52 4.1.1 Experimental Evaluation .................................................................................................. 56 4.1.1.1 Evaluation of Correspondences ................................................................................ 57 4.1.1.2 Camera Orientation .................................................................................................... 59 4.1.1.3 Dense image matching ............................................................................................... 61 4.2 Data Integration Using Accurate Space Resection and SfM Reconstruction Methods... 63 4.2.1 Experimental Evaluation .................................................................................................. 65 4.2.1.1 Camera Orientation .................................................................................................... 66 4.2.1.2 Dense image matching ............................................................................................... 67 4.3 The Proposed General Workflow ........................................................................................... 69 4.3.1 Shifting the Principle Point of the Generated Images .................................................. 72 4.3.2 Advantages of the proposed approach .......................................................................... 72 4.3.2.1 Complementing TLS Point Clouds by Dense Image Matching ........................... 72 4.3.2.2 Automatic Registration of Point Clouds ................................................................. 74 4.3.3 Experimental Evaluation .................................................................................................. 74 4.3.3.1 Camera Orientation .................................................................................................... 74 4.3.3.2 Dense Image Matching .............................................................................................. 78 5 Target-Free Registration of Multiple Laser Scans .................................................................... 79 5.1 Target-Free Registration Using Accurate Space Resection Methods ................................ 79 5.1.1 Experimental Evaluation .................................................................................................. 85 5.1.1.1 Organizing Scans by Similarity ................................................................................ 85 5.1.1.2 Pairwise Registration ................................................................................................. 87 5.2 Target-Free Registration Based on Geometric Relationship of Keypoints ....................... 89 5.2.1 Experimental Evaluation .................................................................................................. 92 5.2.1.1 Organizing Scans by Similarity ................................................................................ 92 5.2.1.2 Pairwise Registration ................................................................................................. 92 5.3 Target-Free Registration Using SfM Reconstruction Method ............................................ 94 5.3.1 Experimental Evaluation .................................................................................................. 95 Contents 5 6 Recording Physical Models of Heritage ..................................................................................... 96 6.1 3D Surveying of the Hirsau Abbey Physical Model ............................................................ 97 6.1.1 TLS Data Acquisition and Processing ............................................................................ 97 6.1.2 Photogrammetric Data Acquisition and Processing .................................................... 97 6.1.3 Final Model ......................................................................................................................... 99 6.2 Summary.................................................................................................................................... 99 7 Case Studies .................................................................................................................................. 103 7.1 Data Acquisition ..................................................................................................................... 103 7.1.1 The Hirsau Abbey ........................................................................................................... 103 7.1.2 The Temple of Heliopolis ............................................................................................... 104 7.1.3 The Applied Sensors ....................................................................................................... 105 7.1.3.1 TLS Systems............................................................................................................... 105 7.1.3.2 Imaging Sensors ........................................................................................................ 107 7.2 Data Integration Results and Evaluations