Practical 5 - Object is to measure the horizontal distance between two terminal stations on PDF

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Object is to measure the horizontal distance between two terminal stations on a sloping ground by Stepping Method and By Using Abney Level.
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Practical # 5 Object : a) To measure the horizontal distance between two terminal stations on a sloping ground by i. STEPPING METHOD. Instruments required : 1. Ranging rods 2. Tape 3. Field book Theory : In case of sloped or hilly ground, the horizontal distance can be measured by stepping method by measuring the line in short horizontal lengths.

Procedure:  Let A and B be the two end stations with sloping ground in between.  First, ranging is carried out to align the rods P and Q with A and B. (There can be more than two intermediate stations e.g. R)  The follower holds the zero end of tape at end station A and directs the leader at P to be in the line of AB and stretch the tape above the ground in horizontal line, then measures the horizontal distance d1.  The leader then transfers his station P to the station Q and stretches the tape horizontally and measures the horizontal distance d2.

 By same procedure all short horizontal lengths i.e. d1,d2 and d3 are measured and are noted in field book.  The horizontal distance D is calculated by the following formula: D=d1+d2+d3. Observations:

Results: Station

Distance (ft)

Distance (m)

AP (d1)

42.58

12.98

PQ (d2)

41.92

12.78

QB (d3)

61.33

18.71

AB (D=d1+d2+d3)

145.83

44.47

ii, USING ABNEY LEVEL Instruments required : 1. 2. 3. 4.

Ranging rods Abney level Tape Field book

Theory:

When the slopes of hill are at greater height and inclined at a certain higher angle, in this case stepping method may not be applicable. In such a case, various slopes are measured by using abney level. By knowing the angle of slope of hill and inclined distance, horizontal distance can be calculated as follows: Let ‘L’ is the inclined distance , ‘µ’ is the angle of slope and ‘D’ is the horizontal distance. Then the required horizontal distance is: D = L cos (µ) Procedure:  Let the end stations are A and B and the intermediate stations are P and Q .  The follower holds the zero end of tape at end station A on the ground, while the leader stretches it inclined at the end station B, such that the tape passes along the foots of the intermediate stations and measures the inclined distance L.

 Then a mark is made on a ranging rod on the end station B at the height of the observers eye at the end station A and measures the angle of slope ‘µ’ and notes all data in the field book.  While measuring the angle , the observer should take care of the target i.e. the mark so that it must be easily visible to him through abney level and the bubble must coincide with the horizontal line as viewed from the eyepiece of abney level.

Results: Station

Sloping Distance ‘L’ Sloping Distance ‘L’ Angle of slope ‘µ’ (ft) (m)

AB

145.83

Calculations: D=L cos µ D=145.83 cos 4.33 D=145.41’ And D=45.45 cos 4.33 D=45.32m

45.45

4.33 degrees...