Roman Surveying

Abstract

IN the Zeitschrift fülr Vermessungswesen (Heft 21, 1911) Prof. E. Hammer discusses the precision with which the nations of antiquity were able to mark out lines on the surface of the earth with the means at their disposal. Taking, first, that portion of the frontier of the Roman Empire which existed as a straight line about 80 kilometres long from near the River Rems in Wurttemburg to the district of Wallfiirn in Baden, he investigates the question whether this line was laid down approximately straight by chance, or whether it was intended to be a straight line and special care was taken to arrive at this result. Points on the line were located and their positions plotted on the cadastral maps (scale 1: 2500), from which their coordinates were determined. From these the direction-angle of portions of the line was calculated, and also the mean departure of points on the boundary line from the true straight line. For a portion amounting to 29 km. of the whole length, the mean error in position of a point on the boundary was found to be 2 metres, which indicates a surprising accuracy in carrying such a line over rough ground, while for portions of it an even greater precision was attained. Further observations by Prof. Leonhard, not yet published, on the remaining 50 kilometres of the boundary indicate that the accuracy is there maintained. The Romans must have fixed a few principal points in prominent positions by signals at night, and then interpolated intermediate points; the observed accuracy could never have been attained by prolonging a line.