
Theodolite used for the Principal Triangulation of Great Britain
1791
1791
1795
1794
1798
1797
1800
1795
1793-1803
1791
1800
1790
1796
1794
1800
1800
1800
1792
1795
1800
1790
1802
1795
1795
1790
1792
1792
1802
1790
1799-1802
1799
1893-4
2000-100 BCE
1788
1801
circa 1801
mid-1800s
1705-1737
1797
1800
1788
1791
1790-1794
1804
1799
1800
1797
1801
4000-2001 BCE
1799
1790