Post on 13-Dec-2015
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Theory of Errors and AdjustmentsLecture 3
Caraga State UniversityCollege of Engineering and Information Technology
Broddett B. Abatayo, GE Lecturer
In a two peg test using model wild NA2 dumpy level, the following observations were taken:
Rod reading Instrument M set
up near at AInstrument P set
up near at B
on point A 1.623 0.362
on point B 2.875 1.622
1. What is the true difference in elevation between A and B?2. Determine the error in the line of sight for the net distance AB ?3. Determine the correct reading at A that will give level line of sight with the instrument still
at point P.
A
B
M
PEG METHOD OF ADJUSTMENTSITUATION 1: SITUATION 1:
P
In a two peg test using model wild NA2 dumpy level, the following observations were taken:
1. What is the true difference in elevation between A and B?2. Determine the error in the line of sight for the net distance AB ?3. Determine the correct reading at A that will give level line of sight with the instrument still
at point P. Ans. 1.) 1.256m 2.) 0.004m 3.) 0.366m
PEG METHOD OF ADJUSTMENT
A
B
SITUATION 1: SITUATION 1:
Rod reading Instrument M set
up near at AInstrument P set
up near at B
on point A 1.623 0.362
on point B 2.875 1.622
The line of sight of a wye level was tested by setting up exactly midway between two points A and B.
Instrument at M Instrument at P
Rod reading on A 1.520m 1.683m
Rod reading on B 1.395m 1.490m
1. What is the true difference in elevation between A and B?2. What is the error in the line of sight?3. Determine the reading at A that will make the line of sight horizontal?
A
B
M
PEG METHOD OF ADJUSTMENTSITUATION 2: SITUATION 2:
The line of sight of a wye level was tested by setting up exactly midway between two points A and B.
Instrument at M Instrument at P
Rod reading on A 1.520m 1.683m
Rod reading on B 1.395m 1.490m
1. What is the true difference in elevation between A and B?2. What is the error in the line of sight?3. Determine the reading at A that will make the line of sight horizontal?
Ans. 1.) 0.125m 2.) 0.068m 3.) 1.615m
A
B
P
PEG METHOD OF ADJUSTMENTSITUATION 2: SITUATION 2:
A
1
To make peg adjustment, the following notes were taken.
Wye level @ 1 Wye level @ 2
Rod reading @ P 0.75m 1.906m
Rod reading @ Q 2.766m 3.789m
Point 1 is on the line PQ and midway between P and Q. Point 2 is on the same line as P and Q but not between them. Point 2 is 25m from P and 230m from Q. With the wye level at point 2, what is the rod reading at P for a level sight?
PEG METHOD OF ADJUSTMENTSITUATION 3: SITUATION 3:
B
To make peg adjustment, the following notes were taken.
Point 1 is on the line PQ and midway between P and Q. Point 2 is on the same line as P and Q but not between them. Point 2 is 25m from P and 230m from Q. With the wye level at point 2, what is the rod reading at P for a level sight?
Ans. 1.921
2
PEG METHOD OF ADJUSTMENTSITUATION 3: SITUATION 3:
A
B
Wye level @ 1 Wye level @ 2
Rod reading @ P 0.75m 1.906m
Rod reading @ Q 2.766m 3.789m
SITUATION 4: SITUATION 4:
A line of levels 6km long is run from BM1 to BM2 with a computed elevation of 165.80m. The average BS and FS distances are 100m and 150m respectively. 1.) It was found out however that the line of sight of the instrument is inclined upward by 0.003m in a distance of 10m. Determine the correct elevation of BM2.
2.) If the level settles by 5mm between the instant of every BS and FS readings. Find the correct elevation of BM2.
3.) If the leveling rod is inclined 4⁰ from the vertical every time the backsight is taken and the average BS reading is 2.4m. Determine the correct elevation of BM2.
SITUATION 4: SITUATION 4:
A line of levels 6km long is run from BM1 to BM2 with a computed elevation of 165.80m. The average BS and FS distances are 100m and 150m respectively. 1.) It was found out however that the line of sight of the instrument is inclined upward by 0.003m in a distance of 10m. Determine the correct elevation of BM2.
2.) If the level settles by 5mm between the instant of every BS and FS readings. Find the correct elevation of BM2.
3.) If the leveling rod is inclined 4⁰ from the vertical every time the backsight is taken and the average BS reading is 2.4m. Determine the correct elevation of BM2.
SITUATION 4: SITUATION 4:
A line of levels 6km long is run from BM1 to BM2 with a computed elevation of 165.80m. The average BS and FS distances are 100m and 150m respectively. 1.) It was found out however that the line of sight of the instrument is inclined upward by 0.003m in a distance of 10m. Determine the correct elevation of BM2.
2.) If the level settles by 5mm between the instant of every BS and FS readings. Find the correct elevation of BM2.
3.) If the leveling rod is inclined 4⁰ from the vertical every time the backsight is taken and the average BS reading is 2.4m. Determine the correct elevation of BM2.
Adjustment of LEVEL CIRCUITSThe known elevation of BM1 is 738.730m. A 30,500km long level circuit is run, closing back on BM1 with an elevation, as determined from the notes, of 728.486m. The observed elevations of other bench marks which were established during the run, and their distances from the initial bench mark are given as follows:
SITUATION 5: SITUATION 5:
Sta Distance from BM1 km
Observed elevation m
BM6
BM1
BM2
BM3
BM5
BM4
BM1 0.000 728.730
BM2 5.245 783.213
BM3 11.271 891.764
BM4 17.718 843.195
BM6 25.247 702.956
BM1 30.500 728.486
BM5 21.964 739.708
3.283km
4.246km
6.447km
6.026km5.245km
728.486m
702.956m
739.708m
843.195m
891.764m
783.213m
728.730m
5.253km
Determine the ff:
1.) The error of closure.2.) Correction to be applied to each observed elevation.3.) Adjusted elevations of the bench marks along the level route.
SITUATION 5: SITUATION 5: Adjustment of LEVEL CIRCUITS
BM6
BM1
BM2
BM3
BM5
BM4
3.283km
4.246km
6.447km
6.026km5.245km
728.486m
702.956m
739.708m
843.195m
891.764m
783.213m
728.730m
5.253km
Determine the ff:
1.) The error of closure.2.) Correction to be applied to each observed elevation.3.) Adjusted elevations of the bench marks along the level route.
Adjustment of LEVEL NETSITUATION 6: SITUATION 6:
- 10.64
- 15.96
+20.64
- 4.95
+4.76
From the level net shown , it is required to compute the adjusted elevations of BM2, BM3 and BM4 if BM1 = 100m.
BM2 – 100 = 20.64BM3 – BM2 = 4.76BM4 – BM3 = -10.64 100 – BM4 = -15.96BM4 – BM2 = -4.95
VARIABLES = CONSTANT
BM2 = 120.64 -BM2 + BM3 = 4.76 -BM3 + BM4 = -10.64 -BM4 = -115.96-BM2 + BM4 = -4.95
ABCDE
BM1
BM2
BM3
BM4
SITUATION 6: SITUATION 6: