
Theodolite used for the Principal Triangulation of Great Britain
1791
1791
1830 (original); 1967 (model)
1815-1825
1795-1805
1821
1801-1830
1822
1829
1829
1801
1801-1830
1793-1803
1794
circa 1805
1798
1797
1893-4
1805
1800
1783-1800
1812
1805-1815
1830
1795
circa 1808
1814
1785-1795
1781-1790
2000-100 BCE
1813
1783
1785
1785
1826
1801-1830
1801-1830
1801-1830
1801-1830
circa 1810
1808
1807
1782-1793
1785-1790
1784
1815
1784
1815
1795-1810
1863-7
1791