Leveling Part II: Differential Leveling

1 / 39

# Leveling Part II: Differential Leveling - PowerPoint PPT Presentation

Faculty of Applied Engineering and Urban Planning. Surveying. Second Semester 2009/2010. Leveling Part II: Differential Leveling. Content. Computation of elevations using Method of Instrument Height Calculations Check Computation of elevations using Method of Rise and Fall

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Leveling Part II: Differential Leveling' - mira-buckley

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Faculty of Applied Engineering and Urban Planning

Surveying

Second Semester 2009/2010

Leveling

Part II: Differential Leveling

Content

• Computation of elevations using Method of Instrument Height
• Calculations Check
• Computation of elevations using Method of Rise and Fall
• Calculations Check

Measuring Elevation Difference Using a level

• The basic operation in differential leveling is the determination of elevation differences between two points
• Consider two points A and B as shown
• Set up the level so that readings may be made on a staff held vertically at A and then at B

B

A

Rise

2.56

0.93

C

B

A

AC = 2.56 – 0.93 = 1.63 m

Fall

0.64

2.97

K

M

NK = 0.64 – 2.97 = -2.33 m

N

Calculation of Elevation

The height of instrument method

Elevation of Point A = 520.43 m AMSL

Height of Instrument HI = Elevation Of A + Staff Reading

= 520.43 + 2.56 = 522.99 m AMSL

Elevation of B = HI – Staff Reading at B

= 522.99 – 0.93 = 522.06 m AMSL

0.93

2.56

C

B

A

Calculation of Elevation

The height of instrument method

Elevation of Point M = 520.43 m AMSL

Height of Instrument HI = Elevation Of M + Staff Reading

= 520.43 + 0.64 = 521.07 m AMSL

Elevation of N = HI – Staff Reading at N

= 521.07 – 2.97 = 518.10 m AMSL

2.97

0.64

K

M

N

Calculation of Elevation

The rise and fall method

Elevation of Point A = 520.43 m AMSL

Elevation Difference = Elevation Of A - Elevation Of B

= 2.56 – 0.93 = 1.63 m (rise)

Elevation of B = Elevation at A + rise

= 520.43 + 1.63 = 522.06 m AMSL

0.93

2.56

C

B

A

Calculation of Elevation

The rise and fall method

Elevation of Point M = 520.43 m AMSL

Elevation Difference = Elevation Of M - Elevation Of N

= 0.64 – 2.97 = - 2.33 m (fall)

Elevation of N = Elevation at M + rise

= 520.43 - 2.33 = 518.10 m AMSL

2.97

0.64

K

M

N

Definitions

Backsight (BS)

This is the first reading taken by the observer at every instrument station after setting up the level

Foresight (FS)

This is the last reading taken at every instrument station before moving the level

Intermediate Sight (IS)

This is any reading taken at an instrument station between the backsight and the foresight

Turning point (TP)

This point at which both a foresight and a backsight are taken before moving the staff

Calculation of Elevation

B

A

1

C

G

D

F

E

BM

RL = 98.76 m AMSL

Plan

G

F

1 BM

B

E

C

D

A

0

20

40

60

80

100

120

Distance (m)

Longitudinal Section

Calculation of Elevation

Instrument Station

1

P

BM

RL = 98.76 m AMSL

Plan

Backsight (BS)

0.663

1 BM

0

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

G

D

F

E

BM

Q

RL = 98.76 m AMSL

Plan

2.270

2.787

1.218

0.646

1.153

1.946

1.008

1.585

0.663

G

F

Q

1 BM

B

P

E

C

D

A

0

20

40

60

80

100

120

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

BM

RL = 98.76 m AMSL

Plan

Intermediate Sights (IS)

1.153

1.946

1.008

0.663

1 BM

B

P

C

A

0

20

40

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

D

BM

RL = 98.76 m AMSL

Plan

Foresight (FS)

1.153

1.946

1.008

1.585

0.663

1 BM

B

P

C

D

A

0

20

40

60

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

D

BM

Q

RL = 98.76 m AMSL

Plan

Turning Point (TP)

Backsight (BS)

2.787

1.153

1.946

1.008

1.585

0.663

Q

1 BM

B

P

C

D

A

0

20

40

60

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

G

D

D

F

E

BM

Q

RL = 98.76 m AMSL

Plan

2.270

2.787

1.218

0.646

1.153

1.946

1.008

1.585

0.663

G

F

Q

1 BM

B

E

P

C

D

A

80

100

120

0

20

40

60

Distance (m)

Distance (m)

Longitudinal Section

Check 1

No. of BS = No. of FS

No. of BS = 2

No. of FS = 2

Check 2

ΣBS - ΣFS = RL of last point - RL of first point

ΣBS - ΣFS = 3.450 – 2.231 = 1.219

RLlast - RLfirst = 99.979 – 98.760 = 1.219

Check 3

ΣRL – RLfirst point = [Σ (No. of IS and FS × HI)] - Σ IS- Σ FS

ΣRL – RLfirst point = 689.741

[Σ (No. of (IS and FS) × HI)] - Σ IS- Σ FS

= [ 99.423×4 + 100.625×3] – 7.595 – 2.231 = 689.741

Calculation of Elevation

B

A

1

C

P

G

D

F

E

BM

Q

RL = 98.76 m AMSL

Plan

2.270

2.787

1.218

0.646

1.153

1.946

1.008

1.585

0.663

G

F

Q

1 BM

B

P

E

C

D

A

0

20

40

60

80

100

120

Distance (m)

Longitudinal Section

Calculation of Elevation

The rise and fall method

Elevation of Point A = 520.43 m AMSL

Elevation Difference = Elevation Of A - Elevation Of B

= 2.56 – 0.93 = 1.63 m (rise)

Elevation of B = Elevation at A + rise

= 520.43 + 1.63 = 522.06 m AMSL

0.93

2.56

C

B

A

Calculation of Elevation

The rise and fall method

Elevation of Point A = 520.43 m AMSL

Elevation Difference = Elevation Of A - Elevation Of B

= 0.64 – 2.97 = - 2.33 m (fall)

Elevation of B = Elevation at A + rise

= 520.43 - 2.33 = 518.10 m AMSL

2.97

0.64

C

A

B

Calculation of Elevation

B

A

1

C

G

D

F

E

BM

RL = 98.76 m AMSL

Plan

G

F

1 BM

B

E

C

D

A

0

20

40

60

80

100

120

Distance (m)

Longitudinal Section

Calculation of Elevation

Instrument Station

1

P

BM

RL = 98.76 m AMSL

Plan

Backsight (BS)

0.663

1 BM

0

Distance (m)

Longitudinal Section

ΔH1A = BS – IS

= 0.633 – 1.946 = -1.283 (fall)

Calculation of Elevation

B

A

1

C

P

D

BM

RL = 98.76 m AMSL

Plan

Intermediate Sights (IS)

Foresight (FS)

1.153

1.946

1.008

1.585

0.663

1 BM

B

P

C

D

A

0

20

40

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

D

BM

Q

RL = 98.76 m AMSL

Plan

Turning Point (TP)

Backsight (BS)

2.787

1.153

1.946

1.008

1.585

0.663

Q

1 BM

B

P

C

D

A

0

20

40

60

Distance (m)

Longitudinal Section

Calculation of Elevation

B

A

1

C

P

G

D

D

F

E

BM

Q

RL = 98.76 m AMSL

Plan

2.270

2.787

1.218

0.646

1.153

1.946

1.008

1.585

0.663

G

F

Q

1 BM

B

E

P

C

D

A

80

100

120

0

20

40

60

Distance (m)

Distance (m)

Longitudinal Section

Check 1

No. of BS = No. of FS

No. of BS = 2

No. of FS = 2

Check 2

ΣBS - ΣFS = ΣRise – ΣFall = RLlast – RLfirst

3.450 – 2.231 = 3.079 – 1.860 = 99.979 - 98.760

1.219 = 1.219 = 1.219