Rheinische Friedrich Wilhelms Universität Bonn Department of Geography Evaluation of different airborne high-resolution digital elevation products in a high alpine environment Diploma Thesis Submitted by Johann Müller Langgasse 23 64409 Messel Supervised by Prof. Dr. Gunter Menz Dr. Isabelle Gärtner-Roer Bonn, December 2011 ACKNOWLEDGEMENT I ACKNOWLEDGEMENT „So long and thanks for all the fish!” The Dolphins First of all, I would like to thank my supervisor Prof. Dr. Menz for his support and encouragement and for giving me all the freedom to follow my interests. I also thank Dr. Isabelle Gärtner-Roer for making this whole work possible in the first place. I owe her the most productive and interesting years of my studies and I am looking forward to any further cooperation. Specials thanks and appreciation go to the ’Swiss connection’, especially to Dr. Christian Ginzler at WSL in Birmensdorf who provided the aerial imagery and showed much patience with my first attempts in photogrammetry. Big thanks go just down the hall at WSL to Patrick Thee who introduced me to the principles of geodetic surveying and who was always an enjoyable mentor and companion in the field. In particular, I thank the entire staff at the center for remote sensing of land surfaces (ZFL) in Bonn who supplied me during the last years not only with professional expertise and fruitful discussions but also with moral support and non -work related projects. I am especially thankful to Dr. Hannes Feilhauer, Dr. Sven Nussbaum and Frank Thonfeld who did more than their share as colleagues and as friends. Several hours of discussion and computer related support have been spent with Benjamin Mack who was also willing to stand by my side at any hour of the day or night. This is hereby also much appreciated. I especially have to thank Jana Junghardt for all the support in any kind of situation and for taking my mind off work when I really needed the distraction. And finally I want to thank my family for all their support and love which led up to this moment. SUMMARY II II SUMMARY Stereoscopic airborne remote sensing is able to generate high-resolution digital elevation models in very remote areas or areas of extreme terrain. Monotemporal and/ or multitemporal digital elevation information can be used to analyze relevant structures and processes within geosystems. Multitemporal data generates information about varying process rates and dynamic changes of landsurface features. Potential hazardous processes can be detected and monitored by high resolution digital elevation products. Within this study three different camera systems (HRSC-A, RC30 and Leica ADS40) are compared and evaluated against a high precision geodetic dataset and an airborne lasers can. Different quality parameters are developed to assess the absolute and relative accuracy of such elevation products in a high-alpine, periglacially-formed environment. Absolute global and local accuracy measures are necessary for quantifying processes and interpreting changes in geosystems. The results show that the vertical accuracy of digital elevation products depends strongly on the inclination of the sampled terrain. The photogrammetric methods face difficulties when performing in steep terrain. The ADS40 system shows the best performance in high alpine areas. The biggest systematic and random errors were identified for the HRSC-A. The findings are discussed due to their relevance in permafrost-related applications and the results of this study contribute to the further application of the sensor systems and their products. LIST OF CONTENTS III III LIST OF CONTENTS Inhalt ACKNOWLEDGEMENT ........................................................................................................ I SUMMARY ........................................................................................................................ II LIST OF CONTENTS ........................................................................................................... III LIST OF FIGURES ................................................................................................................ V LIST OF TABLES .............................................................................................................. VIII ACRONYMS.................................................................................................................... VIII 1 Introduction .......................................................................................................... 1 1.1 Motivation .................................................................................................................... 1 1.2 Objectives ..................................................................................................................... 2 1.3 Conceptional Background .............................................................................................. 3 2 Introduction to remote sensing in earth surface assessment .................................. 4 2.1 Remote sensing systems and their properties ................................................................. 4 3 Digital elevation products in high alpine areas - possibilities and restrictions .......... 8 4 Generation of digital elevation information ......................................................... 11 4.1 Photogrammetry ......................................................................................................... 12 4.2 Airborne Laserscanning ................................................................................................ 18 5 Accuracy assessment of digital elevation products ............................................... 22 5.1 How to assess accuracy ................................................................................................ 23 6 The Hungerlitälli in the Turtmann valley .............................................................. 26 6.1 The Turtmann valley– a general overview .................................................................... 27 6.2 A closer look at the Hungerlitälli .................................................................................. 29 7 High alpine datasets produced and used in this study ........................................... 32 7.1 Description of the photogrammetric sensor systems .................................................... 32 7.1.1 HRSC-A............................................................................................................................................. 32 7.1.2 ADS40 .............................................................................................................................................. 35 7.1.3 RC30 ................................................................................................................................................ 39 7.2 The generation of digital elevation products in the Hungerlitälli ................................... 41 7.3 Reference Data ............................................................................................................ 47 7.3.1 The Airborne Laser Scan .................................................................................................................. 47 7.3.2 Geodetic Field Survey ...................................................................................................................... 48 LIST OF CONTENTS IV IV 8 Evaluation of the digital elevation products in the Hungerlitälli ............................ 51 8.1 The geodetic measurements ........................................................................................ 52 8.2 The Airborne Laser Scan ............................................................................................... 54 8.3 The empirical approach ............................................................................................... 73 9 Discussion of the results in the context of other current studies ........................... 75 10 Application of high resolution DEPs in permafrost research .................................. 79 11 Future prospects and perspectives ....................................................................... 83 12 Conclusion ........................................................................................................... 84 REFERENCES ..................................................................................................................... X DECLARATION OF AUTHORSHIP .................................................................................... XVII LIST OF FIGURES V V LIST OF FIGURES Figure 1. Hyperspectral Cube. (NASA, 2011) ........................................................................................... 6 Figure 2. Principle of repeat pass interferometry (left) by the ERS-1 and ERS-2 sensor systems and the SRTM InSAR (right) (Albertz, 2007) ......................................................................................................... 6 Figure 3. Principle of ALS (Lillesand and Kiefer, 2000) ............................................................................ 7 Figure 4. Working principle photographic CCDs (Kraus, 2004,) ............................................................ 13 Figure 5. Principle of a line camera (left) and a three line camera (right). a, b and c represent the three lines of CCDs and x and y the planar coordinate system (Kraus, 2004, modified). ..................... 14 Figure 6. The three line scanner principle (Fricker, 2001) ...................................................................