Differential Levels 20 Points What does the term elevation m

Differential Levels (20 Points. What does the term elevation mean related to construction projects and how can it be represented? a) (lb) What is the purpose of running hat is the purpose of running elevation levels on a construction site? Three wire (Ic) Which rod reading should be recorded -the highest or lowest? Why should the BS and FS distance from the instrument in differential levels be close to equal? (ld) (le) What is meant by level circuit and arithmetic check? What is EOC and REOC? 2. Given Curve Data: (20 points) PC-I N 57-14-45 E PC 18+75.63 R 1200.00 PI- PT S 43-18-35 E Find: L, C, T, MO, E, Dc, Station of PC and PI

Solution

Prob.1

(a) Elevation is the vertical distance of a point from the Mean Sea Level or any other Bench Mark set at zero elevation at MSL. For ease of surveying different Bench Marks(BM) are set using control points which are used for doind the detailed elevation survey. These points act as the reference point for the Elevation of the new survey stations.

(B) A construction site may need cut and fill, and to determine those two quantities the elevation profile of the road has to be made. Levelling is done to accurate draw the vertical profile of the road.

In three wire leveling three readings of the cross hairs are notes, upper, middle and of bottom one and the upper and lower are averaged to check for any discrepancy.

(c) In three wire levelling all three higher, lower and middle readings are recorded and the two are averaged.

(d) This reduces the errors occuring due to various reasons, such as parallax, instrument error or environmental errors.

(e) A level circuit or loop starts and ends at the same station, i.e. at same elevation. This makes a close loop and therefore provides a check for the errors. If the elevation of the end point does not come out to be same after running calculations for the loop that means there would be some error. An arithmatic check can be made by taking the algebraic sum of back sight(BS) and Foresights(FS) and they both must cancel out each other to zero.