I am certain that several other contributors to this memorial volume have expounded on the many attributes, both professional and personal, of Professor Fritz Ackermann. It is unquestionable that he was a giant in our field, on whose shoulders current and future practitioners shall stand in order to keep the wheels of progress and advancement moving forward.
I feel fortunate and privileged indeed to have closely known him as a friend and colleague during over 50 years that our careers overlapped. I will therefore limit my statements here on the long lasting and unshakable friendship that we shared. Nevertheless, for those readers who wish, they may visit the site:
https://www.isprs.org/documents/archive/Celebrations/Birthday-Ackermann80-091106-Stuttgart/
where they can, search for, and read, my tribute “Fritz Ackermann’s Photogrammetric Journey”. I presented it at his Institute in Stuttgart on 6 November 2009, for his 80th Birthday. In it, I chronicled various aspects of his professional and personal life to that date. We all know that he continued thereafter to be quite active and engaged.
Our relationship started in September 1964, when as a young newly minted PhD in Photogrammetry from Cornell University, I traveled with my advisor to participate in the Pre- ISPRS-Congress Symposium at the ITC in the Netherlands. For me it was a different experience from the ASPRS meetings in the US; different intensity and solemnity and, on occasion, less than cordial atmosphere. It was in this environment that my advisor presented our paper stemming from my PhD dissertation.
In a typical lighthearted American manner, my advisor began by what he thought would be humorous: “ … in the beginning humans were created with two eyes, in 1963 Ed Mikhail developed the three eyed creature … ”. That was a reference in my research to the idea of using image triplets in analytical photogrammetry in place of the image pairs classically used in analog procedures. In the US, this would have led to genuine laughter and been enjoyed by all. Unfortunately, this was not the case in this quite different and serious environment which my professor had totally misjudged. Instead, this lighthearted introduction elicited an opposite reaction and skepticism that such was not serious or worthy research work. My poor advisor was even mockingly referred to as “Padre”!
Visualize now the young fellow in his twenties whose work was thus received. The audience included world-known “who’s who” in the photogrammetric field. What a way to get him so cruelly introduced to the international community of which he was hoping to one day be a part. All I could do was shrink in embarrassment. Then I noticed a robust-looking gentleman sitting in the front row who was stealing glances at me. At the end of the session, he was the only one to approach me. Whereas I thought that he did that out of pity, it was actually more of compassion and understanding.
The Symposium program had listed the attendees’ names, most of whom were well-known researchers and published authors whose work I had encountered during literature review for my dissertation. But I had not met any of them. Had the presentation of our paper gone well, I would have then been able to attempt to introduce myself and meet them. As it were, I simply wanted to remain anonymous, except for that one gentleman who came over and introduced himself as Fritz Ackermann! Naturally, having read his work and held him in high regard, I was moved that he cared enough to reach out to me.
Remarkably, Professor Ackermann did not dwell on the debacle that just occurred. Instead, he briefly said that he was sorry for what had happened and that I should not worry too much about it. He proceeded to ask me pointed questions about my work for which I was, of course, very pleased that he was interested. As an astute scientist, he had listened carefully to the contents of the presentation rather than superficially dismissing it as the others had done. He recognized three ideas: the triplets, relative triangulation of multiple images, and block triangulation of 3-dimensional independent units. Naturally, I responded to his questions enthusiastically and in response to his request gave him a copy of my paper. Coming from a gentleman whose accomplishments I had admired, his remarkable single act of genuine care helped me move from near despair to optimism. A life-long solid friendship was started on that fateful day!
The 1964 ISPRS Congress was held in Lisbon, Portugal, during the two weeks following the ITC Symposium. We met again several times during the Congress and had in-depth discussions on various aspects of analytical photogrammetry. For some reason he thought that I may be an up-and-coming researcher and was generous with his encouragement. Although at that time I was working for a company in Canada, he could tell that my natural inclination was to be an educator and encouraged me to do so. The more he showed interest in my work and ideas, the more I was determined to emulate his path to success in photogrammetric education and research. My chance came the following year when I was asked to establish the graduate program at Purdue University.
We next met at the Symposium on Analytical Photogrammetry at the University of Illinois, Champaign-Urbana, USA, in 1966. Two papers presented by young authors lacked some mathematical rigor. Whereas others were merciless in their criticism, Fritz on the other hand, showed more compassion. He met with the young fellows after the session and made specific recommendations for corrections in order to salvage their work. He never appeared to take any pleasure in seeing them suffer, instead he was kind but firm without ever compromising his stance for rigor and quality. Our friendship grew and we kept in contact until he asked me in 1971 to spend some months at his Institute in Stuttgart during my first sabbatical leave.
In 1960 Fritz was a Lecturer at the ITC teaching, among other subjects, a course on Least Squares. Remarkably, that year I nearly became one of his students, as I was originally going to the ITC for a Masters. Circumstances, however, led me instead to the U.S. and Cornell University. Having deep interest in Least Squares, I had compiled a set of lecture notes on the subject between 1965 and 1971 and took them with me when I joined him to begin my sabbatical leave. My intent was to have him combine my notes with his own notes, to publish a textbook in English, which was badly needed then. Unfortunately, his commitments at the time were such that he could not embark on such an undertaking. Nevertheless, he recognized the value of having such a book and wholeheartedly agreed to support the effort any way he could. I have indelible memories of my time in his Black Forest cottage where I began putting together the manuscript of our book: Observations and Least Squares!
On a personal level, Fritz spared no effort in making my family, especially my two young children, welcome and comfortable. I could almost hear my 2-year old daughter’s squeals of delight coming down the slope from his cottage with him in a sled, and when reaching the bottom saying “Again Uncle Fitz, Pease”! He made our days in Stuttgart quite memorable indeed. Seven years later, I returned with my family on another sabbatical leave and were treated with the same care and kindness. To this day, my older children remember him fondly and were deeply saddened to hear of his passing.
Fritz began his career a few years ahead of mine, during the waning years of the Analog Photogrammetry phase. Both of us then began to contribute at the dawn of the Analytical phase. Remarkably, we viewed the world of Photogrammetry through similar lenses. Naturally, each of us worked in a different environment, had access to different resources, etc., yet we were in agreement on the essential research directions. Furthermore, we had full understanding and respect of each other’s work. I remember with great appreciation his support when I ventured into exploring the photogrammetric potential of holography and holograms, even though it was at the time deemed extraordinary. He provided concrete encouragement by inviting me more than once for presentations to large audiences in Stuttgart. It was most fulfilling to receive such recognition from a gentleman whom I respected and admired greatly.
Fritz and I met many times both here at Purdue and in Stuttgart. We had long walks discussing various issues in the field. The most intense of these was when we were at the cusp of the latest phase, that of digital photogrammetry. We thought it foolhardy then to try and predict the extent and diversity of the advances to come. When one considers the shear explosion that has taken place since then, we were certainly correct not to venture any such predictions!
Fritz was an exceptional and creative scientist; but above all he was a marvelous, warm, human being and my wonderful friend, and for that I am eternally grateful. I shall miss him dearly.