Acknowledgements

First of all, I want to express my gratitude to Prof. Dr. W. Freeden for being an inspiring mentor and for his great and continuous support concerning all the minor and major problems that have come up during my work. I am also much obliged to Prof. Dr. N. Olsen for providing me with MAGSAT data and for reading and evaluating the thesis. It has been a pleasure to meet the former and current members of the Geomathematics Group. I thank Dr. M. Bayer and Dr. R. Litzenberger for the great times we have had together and C. Korb for being the moving spirit of the group. I am very thankful to Dr. O. Glockner for various discussions, for proof-reading the thesis and, last but not least, for being a close friend. A special ”thank you! ” goes out to my ’room mate ’ Dipl.-Math. C. Mayer who has spent hours and hours reading about and implementing numerous gridding methods. Finally, I thank Dipl.-Math.techn. Anna Luther as well as Kai Sandfort for their support concerning the numerics. I thank Prof. Dr. H. Lühr for inviting me (twice) to the GFZ for several days. During these stays he and his co-workers supplied me with useful information that gave me a bette