Remote sensing : a window to/on our world?
Inaugural address delivered by Christoph Kätsch on 15 November 2005. The relatively young scientific field of remote sensing deals with one of the oldest principles applied for orientation and evaluation of the surrounding environment developed during evolution on our planet. Beginning on a very simple level, the first organisms used electromagnetic radiation (mostly the daily sunlight) to raise energy and to collect information on the environment. Evolution finally led to the high end of natural remote sensors, the eye, which forms one of the most important senses for several creatures such as mammals. The eye, along with a high-performance organ, the brain, produces images from the environment, images which allow the individual to interact with others, to react to threats and to look for food. For human beings images, of course, mean much more than a real-time controlling and early-warning system. Images are important aids to seeing, analysing and understanding our world. Together with input from the other four senses, images enabled early scientists to discover, analyse and to define the first scientific principles.This may have started with the first human beings roaming the southern African bushveld and deserts, such as the San, who painted their views, thoughts and experiences on rocks several thousands of years ago. Images can of course show much more than our daily environment only. They can be used to make things visible that are not visible to the eyes, because of the limited perspective of a human being or the limited physical sensitivity of our eyes. Beyond that, they may come from the invisible virtual world of our minds and remain invisible until someone takes a pencil to draw them as images. And that is where the title for this presentation comes from. By analogy with the words of the German poet Rainer Maria Rilke (1875-1926), a contemporary of Albert Einstein, who proposed that poetry and the arts should open up a window on our world, scientists recently demanded that science should help to open this window even wider in special ways in order to help mankind to understand what is going on in the world and how global threats to civilisation may be overcome (cf. Fischer 2004). Obviously the idea of remote sensing will cross one’s mind when thinking about a window on our world. A look through a satellite’s camera or from an aeroplane window onto the earth opens up a really huge window, giving an impressive view onto oceans, land and cities. Rilke’s proposal was, of course, not that simple. He wanted poetry to open a window, and not a mirror, to our world, which allows deep insights into the functioning of the world for the benefit of human beings and for their welfare. He was deeply convinced that the arts and poetry could play a key role in understanding the new world which had been opened by science during his lifetime. It may be presumptuous to say that remote sensing really opened this second dimension of Rilke’s window to our world, but there is no doubt that this discipline contributes much to open a window through which we gained a lot of our current knowledge on our natural environment on earth and even beyond this of the universe. After more than 35 years remote sensing has developed into a complex system which incorporates three main components: first, electromagnetic radiation dealing as the medium for transporting data from remote objects; second, technical components for receiving, registering and storage of data; and finally, the data processing and evaluation of the data in order to derive relevant knowledge – information – from them. This paper aims to demonstrate how this technology has helped to open the window on our world significantly wider. It will give a short overview on the historic developments which led to a booming scientific field; it will then provide some examples on what is possible with today’s knowledge and, finally, present an outlook for specific research needs. Due to the very broad orientation of remote sensing that covers nearly all aspects of our natural, social and economic environment, it will be impossible to consider all relevant fields. The focus will therefore lie on natural resources and the disciplines dealing with them.