Knowing your position on Earth is of vital interest when moving on the sea, in the air or even on land if you leave the road system. During the ancient discovery voyages, at a time when the Earth's surface was only partially explored, position determination was important for outward navigation and for ensuring a safe passage home. Accurate navigation also allowed maps of the newly discovered islands and continents to be drawn.
The classical way of determining geographical positions is the astronomical method using various types of measurements of the Sun and Moon, the planets and the stars. These methods have different degrees of complexity and make use of different instruments, some of which are quite simple to build.
Even with very simple equipment, it is possible to determine your geographical position with a reasonable accuracy. Here is an example of students measuring the solar height, repeating the old "Erathostenes' method". (Pupils at the Rosborg Gymnasium, Denmark).
Nowadays, position determination can also be made using man-made satellites, such as the Global Positioning System (GPS). The GPS is indeed the currently most common system and since some years it has brought enormous advantages in terms of ease of use and reliability to for instance aircraft pilots and sailors (to mention just two categories of users).
It is of course also possible to measure your own position on satellite-based images. In the context of the Sea and Space programme, radar images from the ERS satellite will be made available on which radar reflecting landmarks will be visible.
It is one of the major goals of this sub-programme to illustrate the different types of navigational methods, their advantages and draw-backs. The information necessary to determine topographical positions by the different methods is made available to the participants via the WWW.