chapter 3 chain surveying -...
TRANSCRIPT
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Chapter 3
Chain Surveying
Dr. Mazen Abualtayef
The lecture was prepared by Eng. Heba Hamad, The University of Palestine and modified by
Dr. Mazen Abualtayef, The Islamic University of Gaza
Content
3.1 Introduction
3.2 Equipment used in chain surveying
3.3 Processes in chain surveying
3.4 Mapping details using chain surveying
3.6 Chaining obstacles
3.1 Introduction
Common Methods for Measuring Distances are:
• Pacing
• Taping
• Tachometry which requires angle-measuring
instrument (Theodolite) and rod (Staff).
• EDM (Electronic Distance Measurement) using
light and infrared waves like total station and
measuring from few meters to tens of kilometers.
Type Relative Precision Use
Pacing 1/50 to 1/200 Reconnaissance
استطالع
Taping 1/1,000 to 1/5,000 Land surveys
EDM ±0.04 to 1/300,000 All types of
surveying
Measuring Methods
3.1 Introduction
3.2 Equipment Used in Chain
Surveying
Measurement of Lines:
• Chain
• Tapes
• Invar Tapes: Nickel-steel alloy
3.2 Equipment Used in Chain
Surveying
Making Right Angles:
• Optical Prism
• Cross Staff
3.2 Equipment Used in Chain
Surveying
Others:
• Ranging Rod شاخص
• Arrows
• Pegs أوتاد
• Plumb bobs ميزان الشقلة
• Clinometers مقياس الميل
• Abney Level
3.3 Processes in Chain Surveying
Two types of measurements are performed:
• ranging and measurement of lines
• setting out of right angles
3.3 Processes in Chain Surveying
Take the following points in mind when doing
measurements:
• the measurement should be in a straight line.
• the tape should be reasonably pulled to
minimize sagging or over-stretching.
• systematic way should be followed to count
the number of times the tape is used.
3.3 Processes in Chain Surveying
Ranging and Measurement of Lines:
• Level Ground
• Uniformly Sloping Ground
• Uneven Ground
A. Level Ground
A BA1 A2 A3 A4
Rod Rod
Forward Ranging
3.3 Processes in Chain Surveying
B. Uniformly Sloping Ground
sinα Ld α cos LH
22 dLH
3.3 Processes in Chain Surveying
C. Uneven Ground
3.3 Processes in Chain Surveying
Two cases are to be considered:
- Dropping a perpendicular from point C to a
line AB
- Setting out a line at right angles to another
line AB from a given point C on this line
3.3.2 Setting Out Right Angles
Method 1
Dropping a perpendicular from point C to a line AB
C
3.3.2 Setting Out Right Angles
Method 2
Dropping a perpendicular from point C to a line AB
C
3.3.2 Setting Out Right Angles
Method 3
D F
C
E
BA
Dropping a perpendicular from point C to a line AB
3.3.2 Setting Out Right Angles
Method 4
Dropping a perpendicular from point C to a line AB
C
3.3.2 Setting Out Right Angles
Method 1
Setting out a line to AB from C on the line
3.3.2 Setting Out Right Angles
C
D EC
3.3.2 Setting Out Right Angles
Method 2
Setting out a line to AB from C on the line
F
3 m
4 m
5 m
3.3.2 Setting Out Right Angles
Method 3
Pythagoras
Setting out a line to AB from C on the line
C BA
3.4 Mapping Details
In chain surveying, the topographical and man-
made features are located and mapped
• By measuring with the tape the lengths of a
series of selected reference straight lines,
called chain lines.
• And then locating points on the ground
relative to these lines.
3.4 Mapping Details
Methods of Locating Ground Details
• Method of Ties
• Method of Offsets
3.4 Mapping Details
Before performing any field measurements, the
surveyor should:
• Visit the area to be mapped
• Notice the shape of the area
• Notice the existing details
• Draw reasonable sketch
3.4.1 Choice of Chain Lines
Well-conditioned triangles (Angles 30 – 120)
3.4.1. Choice of Chain Lines
As close as possible to the buildings
3.4.1. Choice of Chain Lines
At least two stations can be seen
3.4.1. Choice of Chain Lines
Minimum Number of Lines
3.4.1. Choice of Chain Lines
Provide check line possibility
3.4.1. Choice of Chain Lines
Avoid obstacles
3.4.2 Booking the Measurements
Considerations to be taken:
• Begin each line at the bottom of a fresh page
• Don’t rely on memory
• Proceed from the bottom to the top
• All details must be sketched roughly to scale
• All other chain lines should be recorded
• Offset are not Drawn and ties are drawn
• Names should be recorded
3.4.2 Booking the Measurements
3.4.3 Plotting the Details
The plotting of details proceeds according to:
• Choose the appropriate scale
• Using Pencil, Begin plotting offsets and ties
• Check the details
• All details are then inked
3.4.3 Plotting the Details
When plotting the details, Try to do the following:
• Make the north to the top of the sheet
• Center the drawing in the middle of the sheet
3.4.3 Plotting the Details
3.6 Chaining Obstacles
Chaining Obstacles:
• Vision is obscured, chaining is possible
• Vision possible, chaining prevented
• Both of vision and chaining prevented
a) Vision obscured, chaining possible
b) Vision possible, chaining prevented
1. Closed Obstacles (Pond)
a. The Parallel Method
b) Vision possible, chaining prevented
K
1. Closed Obstacles (Pond)
b. The Capital Letter A Method
b) Vision possible, chaining prevented
From the similar triangles EDF, FGH
FGEC
FGCGHG
2. Linear Obstacles (River)
a. The First Method
ED
FG
FD
HG
River
FHJG
b) Vision possible, chaining prevented
2. Linear Obstacles (River)
b. The Second Method
River
b) Vision possible, chaining prevented
2. Linear Obstacles (River)
c. The Third Method
River
DF
B
G
E
CA
ED
EC
EF
EG
ED
EFECEG
.
c) Both chaining and vision prevented
FA
GAFCGD
FA
HAFCHE
Random Line
Prolonged Line
c) Both vision and chaining prevented
CD 2MN
A-Method
c) Both vision and chaining prevented