
Theodolite used for the Principal Triangulation of Great Britain
1791
1791
1830 (original); 1967 (model)
1846
1815-1825
1801-1838
1795-1805
1801-1830
1829
1822
1849
1847-1848
1821
circa 1842
1829
1801
1801-1830
1837
1794
1842
1842
1832
1845
1798
1842
1797
1805
1800
1830
1795
circa 1808
1840
1835
1837
1845
1830-1850
1850
1848
1850
1830-1840
1834
1834
1834
1837
2000-100 BCE
1813
1840
1826
1801-1830
1801-1830
1801-1830