chapter 3 chain surveying -...

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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