The Contributions of Geodesy to Geography

The determination of the shape and size of the earth and the location of places on its surface, referred to selected fundamental planes, are the geodesist's principal contributions to geography. The earliest geographers must have found it very difficult to carry on their operations, owing to lack of knowledge of the shape and size of the earth and of the true relative positions of the areas under investigation. A very good value for the size of the earth was obtained from the measurement by triangulation of a meridional are of about 81/, degrees extending north and south of Paris by Domenico and Jacques Cassini betweeni the years 1683 and 1716.1 But the fact that the earth's mean figure is an oblate spheroid was only discovered as a result of the observations made in Peru and in Lapland. This work was begun in 1735.2 The first near approach to the actual figure of the earth resulted from trialgulation done in the last decades of the eighteenth century to connect the observatories of Paris and Greenwich and to determine the length of the earth's meridian quadrant. For the latter purpose an are of the meridian of nearly ten degrees was measured in France. One ten-millionth of the resulting length was adopted as the standard of length (the meter). Any other length could have been selected, as the standard for the meter bears no such exact relation to a quadrant, as later and more accurate data show.3 Geodesists were very active during the nineteenth century, and will be for some time to come, in making geodetic measurements to determine the mean figure of the earth with greater and greater precision. There comes a time, for any given area, when it is useless to add more geodetic data for the purpose of obtaining a more nearly exact mean figure, for there are constant or systematic errors present in the data the effect of which is probably much greater than that of the accidental errors

Geodesy · Geography · Geographic Information Systems Studies · Geophysics and Gravity Measurements · Historical Geography and Cartography

• Measuring zero at sea

  Open Access•Wilko Graf Von Hardenberg•Journal of Historical Geography•2020

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