Abstract
Abstract A geodetic levelling network was established in the main campus of the Ahmadu Bello University, Zaria, in 1976. This network, which initially consisted of 17 lines and 10 junction points with a total length of 11 km, was extended in 1979 by the addition of new bench marks bringing the total length of levelling to 18 km. A recovery levelling to replace lost bench marks and further extend the net was carried out in 1983, resulting in a total length of levelling of 27 km, made up of 21 links and 11 junction points. Repeated levelling carried out in 1979, 1980, 1983 and 1990 shows that no significant movement had occurred at the marks. By 1983 the apparent vertical movement of any of the bench marks sited in 1976 was less than 1 mm. For the bench marks established in 1978 the apparent movement was less than 5 mm in the first year after emplacement, and less than 1 mm by 1983.
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