Object 20

Trimble Navigation 4000SL
GPS Receiver
USA, 1988
Antenna (mod. 12333) and computer (mod. 12331)
National Geographic Institute
Inv. G 206

The GPS receiver seen here was the first to be used by staff at the NGI Geodesy department in the late 1980s.
Geodesy – from the Greek gễ (Earth) and daíô (to divide), literally meaning “measuring the earth” - is vital in map making.

Mercator (1512-1594) was able to make a world map in 1540 because he knew the astronomical position of the cities. Until then, all observations since the Middle Ages had been made on Earth.
At the end of the 17th century, Abbot Picard and Jean-Dominique Cassini used the Borda repeating circle for the triangulation of the Paris Meridian. In this way, they attempted to calculate the Earth's curvature.

With the launch of the Russian Sputnik in 1957 came the challenge of communication between earth and space. Controlling the Apollo 11 from the Earth and the landing of the first person on the Moon in 1969 was only possible because of American military bases all over the world.

In 1978, the US Department of Defense decided to put a constellation of 24 satellites into controlled orbit to help with rocket guidance. The entire system became operational in 1993…four years after the fall of the Berlin wall (1989). The GPS or Global Positioning System was born and the Earth has been measured from space ever since.

Some years later, the great nations, not wanting to be dependent on the American system, launched their own projects, for example Galileo in the European Union, Glonass in Russia and Beidou in China.

Meanwhile, GPS devices have become an everyday tool and are commonly used by both car drivers and hikers.

A GPS receiver receives signals from a minimum of four satellites and its computer calculates its position in real time compared to this constellation.
Currently, the NGI is in the process of examining which corrections must be made to its instruments. These corrections are, for example, linked to antennae construction. Thanks to large data sets, our devices allow us to obtain a millimetre precision in x and y and to omit a precision of 5 to 8 millimetres in height. These data sets also serve to correct errors caused by environmental wave refraction and reflection.

François Schuiten
Les cités obscures. L’archiviste / De duistere steden. De archivaris
Sc : Benoît Peeters
Casterman, 1987



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