FINAL DATA SHEET

FIELD WORK 5 DIFFERENTIAL LEVELING WITH AND WITHOUT TURNING POINTS

DATE: AUG 9, 2011 GROUP NO. 2TIME: 12:00 PM LOCATION: MURALLA ST. (WALLS)

A. DIFFERENTIAL LEVELING: WITHOUT TURNING POINT (SINGLE SET-UP)

STATION BS FSDIFFERENCE IN

ELEVATION

MEAN or MOST PROBABLE DIFFERENCE

IN ELEVATIONA 1.365 m 300 m

300.0125 mB 1.34 m 300.025 m

B. COMPUTATIONS:

Diff. in ELEV = ELEV1 + BS – FS= 300m + 1.365 – 1.34

Mean Diff. in ELEV = (ELEV1 + ELEV2)/2= (300 + 300.025)/2

C. DIFFERENTIAL LEVELING: WITH TURNING POINT (SINGLE RODDED)

STATION BS HI FS ELEVATION REMARKSBM-1 1.365 301.365 300 m Benchmark 1TP-1 1.335 301.36 1.34 300.025 Turning PointTP-2 1.34 301.35 1.35 300.01 Turning PointBM-2 1.335 301.365 1.32 300.03 Benchmark 2TP-3 1.305 301.345 1.325 300.04 Turning PointTP-4 1.3375 301.355 1.3275 300.0175 Turning PointBM-1 1.325 300.03

Mean Diff. in ELEV = 300.0125 mDiff. in ELEV = 300.025 m

D. COMPUTATIONS:

a) Computations of HI’s and Elevation of Stations

300.000 (Elev BM1) 300.030 (Elev BM2)+ 1.365 (BS on BM1) + 1.335 (BS on BM2)301.365 (HI1) 301.365 (HI4)

- 1.340 (FS on TP1) - 1.325 (FS on TP3)300.025 (Elev TP1) 300.040 (Elev TP3)

+ 1.335 (BS on TP1) + 1.305 (BS on TP3)301.360 (HI2) 301.345 (HI5)- 1.350 (FS on TP2) - 1.3275 (FS on TP4)300.010 (Elev TP2) 300.0175 (Elev TP4)

+ 1.340 (BS on TP2) + 1.3375 (BS on TP4)301.350 (HI3) 301.355 (HI5)- 1.320 (FS on BM2) - 1.325 (FS on BM1)300.030 (Elev BM2) 300.030 (Elev BM1)

b) Arithmetic Check

300.0000 (Elevation of BM1)+ 8.0175 (ΣBS)308.0175

- 7.9875 (ΣFS)300.0300 (Checks with Elevation of BM1)

E. SKETCH:

CONCLUSION

I conclude that through differential leveling, we are able to determine elevations in the field to locate points at specified elevations. And that in leveling a ground, there will not always be a constant elevation in every point. Therefore, in order to measure the different elevations, we will be doing a type of leveling called differential leveling, where the ground is measured from its back and front sights, and is used to get the correct elevation and height of the instrument.

RELATED RESEARCH

Survey Specifications

Sight Distances Sight distances and the balance between foresights and backsights are critical to maintaining accuracy in differential leveling. Sight distances should be reduced when poor environmental conditions are encountered. Under normal conditions the specified sight distances in this Chapter will produce surveys that meet the Department’s accuracy standards for second-order, third-order, and general-order surveys.

Turning Points Turning points (TP) should be set in stable, protected locations. Spikes or large nails set in pavement; wooden stakes set in firm soil; prominent points such as rock outcroppings or the top of concrete curbs may be used as turning points. Each turning point should have a definite high point or be marked at the exact point of rod contact. If a permanent TP

cannot be driven, then a turning plate (“trivet” or “turtle”) weighing at least 15lbs. should be used. In situations allowing neither turning pins nor turning plates,(sandy or marshy soils) a long wooden stake with double-headed nail should be driven to a firm depth. Turning points (except turning plates) should not be removed after use, but left in place to provide a check in the event of blunders or excessive misclosures. A solid, well defined turning point may be used as a temporary benchmark (TBM).

BenchmarksEstablish benchmarks with physical characteristics and quality commensurate with the order of the leveling survey. Benchmarks should be of a stable, permanent nature; e.g., galvanized steel pipe; steel rod driven into a firm soil base; or cast in place concrete. A brass disk epoxied into a drilled hole in rock or concrete is also acceptable.