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LEVELS & LEVELING Major Joarder Md sarwar Mujib Instructor Class B Dept of CE MIST, Mirpur, Dhaka Ref: 1. Surveying – Vol I by Punmia 2. Surveying by Aziz & Shahjahan

Survey 6 Leveling)

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Page 1: Survey 6 Leveling)

LEVELS & LEVELING

Major Joarder Md sarwar Mujib

Instructor Class B

Dept of CE

MIST, Mirpur, Dhaka

Ref:

1. Surveying – Vol I by Punmia

2. Surveying by Aziz & Shahjahan

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A level is an instrument by which the relative heights of different points on the surface of the earth are determined

LEVEL

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Leveling is the process by means of which the difference in elevation ( relative height) of various points on the earth’s surface is calculated/determined

LEVELING

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LEVELING INSTRUMENT• Level with Tripod

• Leveling Staff

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Methods of Leveling

Barometric LevelingTrigonometric LevelingSpirit Leveling ( Direct Leveling)

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Types of Level

Dumpy LevelWye ( or Y ) LevelReverse LevelTilting Level

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What these means ?

Level Surface

Level Line

Horizontal Plane

Horizontal Line

Vertical Line

Datum

Elevation

Vertical Angle

Mean Sea Level (MSL)

Bench Mark (BM)

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How to ?

Set the Level in the field + Important Aspects

Hold the Staff + Important Aspects

Take a reading + Important Aspects

Hand Signal while taking Reading

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Adjustment of Level

Temporary/ Situation Adjustment Setting Up

Leveling Up

Elimination of Parallax

Focusing the Eye Piece

Focusing the Objective

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Adjustment of Level

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NO TILTING

HOLDING A LEVELING STAFF

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Point of interest

Bottom plane of staff

Bottom plane of staff

Point of interest

Error

(a) (b)

Base of Staff at Slope

Correct Incorrect

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Take a Reading

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Alignment during taking reading

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How Staff Looks

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Reading Staff

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Terms & Abbreviations

Station

Height of Instrument (H.I.)

Back Sight (B.S.)

Fore Sight (F.S.)

Turning Point (T.P.)

Intermediate Station (I.S.)/ Change Point

Reduced Level (R.L.)

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Leveling at Level Surface

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Leveling at Slope

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Points to remember before the start

• What is the approximate height difference between points?

• Where should the level be placed to ensure– Visibility of back and forward stations– efficiency of work

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Methods of Calculating R.L.

Rise and Fall Methods

Height of Instrument / Line of Collimation Methods

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– Compute all rises & falls

Start at a BM with known RL To get RL of next station:

• add rise to previous RL, or • subtract fall from previous RL

Repeat for all subsequent stations

Rise & fall method

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remarks

Back Inter Fore Rise Fall

Sum

Check : Sum of Back Reading ~Sum of Fore Reading

= Total Rise ~ Total Fall

= Last R.L. ~ First R.L.

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remarks

Back Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remark

sBack Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

50 7.24

100 6.46

150 5.38

200 6.55

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remark

sBack Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

50 7.24 1.82 98.18

100 6.46 0.78 98.96

150 5.38 1.08 100.04

200 6.55 1.17 98.87

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remarks

Back Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

50 7.24 1.82 98.18

100 6.46 0.78 98.96

150 5.38 1.08 100.04

200 6.55 1.17 98.87

B 75°45' 250 8.78 6.92 0.37 98.50 Change Pt

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Rise & Fall MethodStation Bearing Distanc

eStaff Reading Difference R.L. Remark

sBack Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

50 7.24 1.82 98.18

100 6.46 0.78 98.96

150 5.38 1.08 100.04

200 6.55 1.17 98.87

B 75°45' 250 8.78 6.92 0.37 98.50 Change Pt

300 8.52 0.26 98.76

350 6.24 0.28 101.04

400 5.96 0.28 101.32

450 6.35 0.39 100.93

500 7.54 1.19 99.74

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remarks

Back Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

50 7.24 1.82 98.18

100 6.46 0.78 98.96

150 5.38 1.08 100.04

200 6.55 1.17 98.87

B 75°45' 250 8.78 6.92 0.37 98.50 Change Pt

300 8.52 0.26 98.76

350 6.24 0.28 101.04

400 5.96 0.28 101.32

450 6.35 0.39 100.93

500 7.54 1.19 99.74

Sum 14.20 14.46 4.68 4.96

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Rise & Fall MethodStation Bearing Distance Staff Reading Difference R.L. Remarks

Back Inter Fore Rise Fall

A 46°15' 00 5.42 100 B.M.

50 7.24 1.82 98.18

100 6.46 0.78 98.96

150 5.38 1.08 100.04

200 6.55 1.17 98.87

B 75°45' 250 8.78 6.92 0.37 98.50 Change Pt

300 8.52 0.26 98.76

350 6.24 0.28 101.04

400 5.96 0.28 101.32

450 6.35 0.39 100.93

500 7.54 1.19 99.74

Sum 14.20 14.46 4.68 4.96

Check : Sum of Back Reading ~Sum of Fore Reading= Total Rise ~ Total Fall

14.20 ~ 14.46=0.26 4.68 ~4.96=0.26

Last R.L. ~ First R.L. =99.74 ~100=0.26

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Any Question about Rise & Fall Method ?

????????

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Height of Instrument MethodStation Bearing Distance Staff Reading Ht of Instrument R.L. Remarks

Back Inter Fore

Check : Sum of Back Reading ~Sum of Fore Reading

= Last R.L. ~ First R.L.

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Height of Instrument MethodStation Bearing Distance Staff Reading Height of

InstrumentR.L. Remarks

Back Inter Fore

A 46°15' 00 5.42 100 B.M.

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Height of Instrument MethodStation Bearing Distance Staff Reading Height of

InstrumentR.L. Remarks

Back Inter Fore

A 46°15' 00 5.42 105.42 100 B.M.

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Height of Instrument MethodStation Bearing Distance Staff Reading Height of

InstrumentR.L. Remarks

Back Inter Fore

A 46°15' 00 5.42 105.42 100 B.M.

50 7.24

100 6.46

150 5.38

200 6.55

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Height of Instrument MethodStation Bearing Distance Staff Reading Height of

InstrumentR.L. Remarks

Back Inter Fore

A 46°15' 00 5.42 105.42 100 B.M.

50 7.24 98.18

100 6.46 98.96

150 5.38 100.04

200 6.55 98.87

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Height of Instrument MethodStation Bearing Distance Staff Reading Height of

InstrumentR.L. Remarks

Back Inter Fore

A 46°15' 00 5.42 105.42 100 B.M.

50 7.24 98.18

100 6.46 98.96

150 5.38 100.04

200 6.55 98.87

B 75°45' 250 8.78 6.92 107.28 98.50 Change Pt

300 8.52 98.76

350 6.24 101.04

400 5.96 101.32

450 6.35 100.93

500 7.54 99.74

Sum

Check : Sum of Back Reading ~Sum of Fore Reading

= Last R.L. ~ First R.L.

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Height of Instrument MethodStation Bearing Distance Staff Reading Height of

InstrumentR.L. Remarks

Back Inter Fore

A 46°15' 00 5.42 105.42 100 B.M.

50 7.24 98.18

100 6.46 98.96

150 5.38 100.04

200 6.55 98.87

B 75°45' 250 8.78 6.92 107.28 98.50 Change Pt

300 8.52 98.76

350 6.24 101.04

400 5.96 101.32

450 6.35 100.93

500 7.54 99.74

Sum 14.20 14.46

Check : Sum of Back Reading ~Sum of Fore Reading= Last R.L. ~ First R.L.

14.20 ~ 14.46=0.26 99.74 ~100=0.26

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Any Question about Height of Instrument Method ?

????????

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Drawing of Profile on a Graph Paper

• Approx profile of Leveling

0 50 100 150 200 250

100 ft

100 98.18 98.96 100.04 98.87 98.50

Page 42: Survey 6 Leveling)

R

O

AC

B

LEVEL

STAFF

OAC :

(OC)2 = (AC)2 (OA)2

Or, (R+h)2 = l2 + R2

Or, R2+ 2Rh+h2 = l2 +R2

So, h = l2/(2R+h)

Since R >>> h

So, h = l2/(2R)

R= 6370 km

R

h

The Earth

l

EFFECT OF CURVATURE & REFRACTION ON LEVELING

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Problem on Effect of Curvature

• A student of MIST standing on a deck of a ship just sees a light house ( 42 meter above MSL). Height of student eye is 6 meter from sea level. Find the distance of MIST student from the light house.

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Two Peg Test

x x

A

y

A

B

y

B

x x

y2y

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Problem on Two Peg Test• Point A and B have known RL of 100

and 101 meter respectively. During leveling the H.I. was 102 meter and Staff Reading was 4.0 meter at B. What will be Staff Reading of point A ?

100 meter 100 meter

A B 101C 100

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Special Methods of Leveling

Differential / Fly Leveling

Profile Leveling

Cross-Sectioning

Reciprocal Leveling

Precise Leveling

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Errors in Leveling

Instrumental Imperfect Adjustment

Sluggish Bubble

Incorrect Marking on Staff

Defective joint of Staff

Wear at Staff bottom

Misalignment of Telescope

Accumulation of Dirt at base of Staff

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Errors in Leveling

Natural Curvature of the Earth

Refraction

Temperature

Wind vibration on Level & Staff

Soft Ground

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Errors in Leveling

Personal Handling of Instrument

Verticality of Staff

Mistakes in taking Staff Reading

Mistakes in Recording

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Any Doubt on Leveling as a whole