SECTION B $-$ ANSWER ANY THREE OUESTIONS

QUESTION ONE

DIFFERENTIAL LEVELLING

Describe how the levelling operation was done in the picture above. $(5)$

The following consecutive readings were taken with a level and $5$ meter levelling staff on continuously sloping ground at a common interval of $20$ metres: $0\mathrm{.}385,1\mathrm{.}030,1\mathrm{.}2525,2\mathrm{.}825,3\mathrm{.}730,4\mathrm{.}685,0\mathrm{.}625,2\mathrm{.}005,3\mathrm{.}110$ and $4\mathrm{.}485.$ The reduced level of the first point was $208\mathrm{.}125$ m $.$ Calculate the reduced levels of the points by rise and fall method and also the gradient of the line joining the first and the last point $(10)$

In order to find the difference in elevation between two points A and $B,$a level was set upon the line $AB,60$ metres from A and $280$ metres from B $.$ The readings obtained on staff kept at A and $B$ was $0\mathrm{.}545$ m and $3\mathrm{.}920$ m respectively. Find the true difference in elevation between A and B$.$ and draw the sketch to support your answer. $(5)$