Born Mar. 5, 1852, in Stockholm; died Nov. 24, 1923. Swedish astronomer and geodesist.
Jäderin was a professor of topography and geodesy at the Stockholm Higher Technical School (from 1878) and a university professor at Uppsala (from 1907). In 1898 he headed a preliminary expedition to Spitsbergen to make preparations for arc and angle measurements, and from 1899 to 1902 he directed the Swedish party of a joint Russo-Swedish expedition that conducted geodetic, topographical, and astronomical research in Spitsbergen. In 1880 he invented a base line instrument for measuring the bases of triangulation; the instrument consisted of wires with scales suspended under constant tension from special mounts.