Levelling+Rise+&+Fall+Method

Leveling

Rise & Fall Method

A closed traverse to measure heights at 5.0m intervals is to be taken through the center of a large residential block. There are two existing structures on site that will obscure the view to some of the positions. STEP 1 Set up the instrument where the benchmark can be viewed within correct parameters and a reasonable number of sights can be viewed. This location is identified as L1. STEP 2 Read a backsight to the benchmark that is on the kerb and gutter (1.575) and book this your field notes. This is recorded as a backsight and establishes the height of the instrument above the benchmark. The actual Reduced Level of the Bench Mark is also recorded.

Booking SheetSurveyor______________________ Instrument No___________________Backsight Intermediate Sight Foresight Rise Fall

Chainmen_________________________________ Date__________________Reduced Level

1.575

47.195

Top Bottom 1.817 1.377

Dist Remarks 44.000 BM

STEP 3 Sight and Book all intermediate sights that can be viewed from station S1 to S4.



1.575 1.250 0.850 1.330 1.580

47.195


Dist Remarks 44.000 BM Station 1 Station 2 Station 3 Station 4

STEP 4 The sight to S5 will be a change point so it will be recorded as a foresight. Note when moving the instrument the change point at S5 will become a backsight for the new set up.



1.575 1.250 0.850 1.330 1.580 1.450

47.195


1.570

1.330

Dist Remarks 44.000 BM Station 1 Station 2 Station 3 Station 4 24.000 S5 (CP)

STEP 5 Move instrument to position L2 and read backsight to changepoint S5



1.575 1.250 0.850 1.330 1.580 1.450 2.550

47.195


1.570 2.680

1.330 2.420

Dist Remarks 44.000 BM Station 1 Station 2 Station 3 Station 4 24.000 S5 (CP) 26.000 S5 (CP)

STEP 6 Sight and Book all intermediate sights that can be viewed from station L6 to L10. At this point all required observations required for the task have been taken. This is called an open traverse, we need to close the survey to check for errors.



1.575 1.250 0.850 1.330 1.580 1.450 2.550 1.980 1.760 1.710 1.840 1.920

47.195


1.570 2.680

1.330 2.420

Dist Remarks 44.000 BM S1 S2 S3 S4 24.000 S5 (CP) 26.000 S5 (CP) S6 S7 S8 S9 S10

. STEP 7 Take sight to S11 this will be a change point so it will be recorded as a foresight. Note when moving the instrument the change point at S11 will become a backsight for the new set up.



1.575 1.250 0.850 1.330 1.580 1.450 2.550 1.980 1.760 1.710 1.840 1.920 3.250

47.195


1.570 2.680

1.330 2.420

Dist Remarks 44.000 BM S1 S2 S3 S4 24.000 S5 (CP) 26.000 S5 (CP) S6 S7 S8 S9 S10 S11 (CP)

STEP 8 Take backsight to Sll than close traverse with foresight to B.M.

Surveyor______________________ Instrument No___________________Backsight Intermediate Sight Foresight Rise Fall


1.575 1.250 0.850 1.330 1.580 1.450 2.550 1.980 1.760 1.710 1.840 1.920 3.250 1.831 1.258

47.195


1.570 2.680

1.330 2.420

3.400 2.021 1.418

3.100 1.641 1.098

Dist Remarks 44.000 BM S1 S2 S3 S4 24.000 S5 (CP) 26.000 S5 (CP) S6 S7 S8 S9 S10 30.000 S11 (CP) 38.000 S11 (CP) 32.000 BM

STEP 9 Total Backsights column and Tally Foresight column



1.575 1.250 0.850 1.330 1.580 1.450 2.550 1.980 1.760 1.710 1.840 1.920 3.250 1.831 1.258 5.956 5.958

47.195


1.570 2.680

1.330 2.420

3.400 2.021 1.418

3.100 1.641 1.098

Dist Remarks 44.000 BM S1 S2 S3 S4 24.000 S5 (CP) 26.000 S5 (CP) S6 S7 S8 S9 S10 30.000 S11 (CP) 38.000 S11 (CP) 32.000 BM 194.000

As the survey is a closed the Backsights should equal the foresights. Due to errors and limitations of the instruments there may be a discrepancy this is called a misclose. To determine misclose Backsight 5.956 Foresight 5.958 -0.002mm

Note always remember to take foresight from backsight and note negatives

In this case as there is only a -2mm misclose(Foresight is Larger than Backsight. The allowable misclose 12 x SQRT (0.194)= +/- 5.2mm therefore results are OK STEP 10 The next step is to determine the rises and falls and book them in the appropriate column. When a sight has lesser elevation than the previous sight, it will be classified as a Rise. When a sight has a greater elevation than the previous sight, it will be classified as a Fall.



1.575 1.250 0.850 1.330 1.580 1.450 2.550 1.980 1.760 1.710 1.840 1.920 3.250 1.831 1.258 5.956 5.958 0.573 2.268 -2.270 0.570 0.220 0.050 -0.130 -0.080 -1.330 0.325 0.400 -0.480 -0.250 0.130

47.195


1.570 2.680

1.330 2.420

3.400 2.021 1.418

3.100 1.641 1.098


The Rise & Fall columns are then totaled. The misclose should be the same as the previous result (-2mm)

STEP 11 The Reduced Levels are now calculated by adding the rises and subtracting the falls. Each measurement is either added or subtracted from the previous Reduced Level starting at the known benchmark.



1.575 1.250 0.850 1.330 1.580 1.450 2.550 1.980 1.760 1.710 1.840 1.920 3.250 1.831 1.258 5.956 5.958 0.573 2.268 -2.270 0.570 0.220 0.050 -0.130 -0.080 -1.330 0.325 0.400 -0.480 -0.250 0.130

47.195 47.520 47.920 47.440 47.190 47.320 47.890 48.110 48.160 48.030 47.950 46.620 47.193 -0.002


1.570 2.680

1.330 2.420

3.400 2.021 1.418

3.100 1.641 1.098


The Final Calculated Reduced Level should match the previous calculations

Starting Bench Mark Misclose Ending R.L.

47.195 (Known) + - 0.002 47.193

Therefore we would be reasonably confident that this traverse is accurate within the required parameters.

Traverse Exercise No 2



Top

Bottom

Dist

Remarks

Traverse Exercise 3



Top

Bottom

Dist

Remarks

Other references

Good graphical display of Rise & Fall Leveling http://www.sli.unimelb.edu.au/planesurvey/prot/topic/top04-04-03.html

Documents

Levelling+Rise+&+Fall+Method