To Collect Data for Profile Leveling of a Proposed Road Using Auto Level.

Object: To collect data for profile leveling of a proposed road using Auto Level.

Object: To determine the reduced level of the existing road (profile leveling) with the height of the instrument method.

Theory:

Leveling is the process used to determine a difference in elevation between two points in the vertical plane.

The Height of Instrument method of leveling uses the height of the instrument to find the reduced levels of the road. The reduced level of a station, often called the elevation or height, is the vertical distance between the station and the permanent benchmark. The reduced levels of the stations determine the actual heights of different points on the field. In the case of profile leveling of a road, the level of the road can be determined at different points by reading the road profile level. After knowing the reduced levels of different points on the road, the profile of the road can be obtained, which can be used for different purposes.

Instrumentsrequired:

1. Rope (150m)
2. AutoLevel
3. Tripod Stand
4. Staff rod
5. Chalk (for marking)

Procedure:

1. Place the staff over a benchmark (BM), whose reduced level is known, and set up the Auto Level in a convenient and safe location where BM (station A) is visible. Take the staff reading, known as back sight (B.S.).
2. Place the staff over station B. Take the staff reading, known as intermediate sight (I.S.).
3. Repeat step 2 for the stationsCandD.
4. Take the last reading over the station E for this position, known as Foresight (F.S.).
5. Now, move the instrument to a new position (position 2) and take the reading on the previous position of the staff (over E). This position of a staff is known as the change point (C.P.) or turning point (T.P.), and this reading will be back sight (B.S.).
6. Shift the staff over to station F. Take the staff reading, i.e. I.S.
7. Repeat step 6 for the stationsGandH.
8. Take the last reading e. F.S. over the stationIfor this position.
9. Now, move the instrument again to a new position (position 3) and take the reading on the previous position of the staff (over I). This will be the second C.P.
10. Shift the staff over station J. Take the staff reading, i.e. I.S.
11. Take the last reading, e.g., F.S., over the stationKfor this position.
12. Now, move the instrument again to a new position (position 3) and take the reading on the previous position of the staff (over K). This will be the third C.P.
13. Shift the staff over station L. Take the staff reading, i.e. I.S.
14. Repeat step 6 for stations M,N,andO.
15. Take the last reading, e.g., F.S., over the stationPfor this position.

Results:

Formulaeforcalculations:

• Height of Instrument(H.I)=Known R.L at M/C.P + B.S
• ReducedLevel =I – I.S./F.S.

ApplyingCheck:

∑B.S–∑F.S=Last R.L–FirstR.L

GraphicalRepresentationofResults:

Observationinthefield: