survey 6 leveling)
TRANSCRIPT
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
A level is an instrument by which the relative heights of different points on the surface of the earth are determined
LEVEL
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
LEVELING INSTRUMENT• Level with Tripod
• Leveling Staff
Methods of Leveling
Barometric LevelingTrigonometric LevelingSpirit Leveling ( Direct Leveling)
Types of Level
Dumpy LevelWye ( or Y ) LevelReverse LevelTilting Level
What these means ?
Level Surface
Level Line
Horizontal Plane
Horizontal Line
Vertical Line
Datum
Elevation
Vertical Angle
Mean Sea Level (MSL)
Bench Mark (BM)
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
Adjustment of Level
Temporary/ Situation Adjustment Setting Up
Leveling Up
Elimination of Parallax
Focusing the Eye Piece
Focusing the Objective
Adjustment of Level
NO TILTING
HOLDING A LEVELING STAFF
Point of interest
Bottom plane of staff
Bottom plane of staff
Point of interest
Error
(a) (b)
Base of Staff at Slope
Correct Incorrect
Take a Reading
Alignment during taking reading
How Staff Looks
Reading Staff
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.)
Leveling at Level Surface
Leveling at Slope
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
Methods of Calculating R.L.
Rise and Fall Methods
Height of Instrument / Line of Collimation Methods
– 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
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.
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.
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
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
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
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
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
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
Any Question about Rise & Fall Method ?
????????
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.
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.
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.
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
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
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.
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
Any Question about Height of Instrument Method ?
????????
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
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
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.
Two Peg Test
x x
A
y
A
B
y
B
x x
y2y
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
Special Methods of Leveling
Differential / Fly Leveling
Profile Leveling
Cross-Sectioning
Reciprocal Leveling
Precise Leveling
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
Errors in Leveling
Natural Curvature of the Earth
Refraction
Temperature
Wind vibration on Level & Staff
Soft Ground
Errors in Leveling
Personal Handling of Instrument
Verticality of Staff
Mistakes in taking Staff Reading
Mistakes in Recording
Any Doubt on Leveling as a whole