Scribd
Upload
76 views4 pages

Surveying Peocedure

The document describes various methods for measuring distances that are obstructed during surveying measurements. It outlines three methods for dealing with obstacles to measurement, such as ponds or rivers, which obstruct the chain line but not the view. It also provides two methods for obstacles to alignment, which obstruct both the chain line and view, such as buildings. The document specifies calculating the obstructed distances using principles of similar triangles for each method. Students are then assigned to conduct experiments in the field to measure obstructed distances using these procedures.

Uploaded by

Enriquez Martinez May Ann
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
76 views4 pages

Surveying Peocedure

The document describes various methods for measuring distances that are obstructed during surveying measurements. It outlines three methods for dealing with obstacles to measurement, such as ponds or rivers, which obstruct the chain line but not the view. It also provides two methods for obstacles to alignment, which obstruct both the chain line and view, such as buildings. The document specifies calculating the obstructed distances using principles of similar triangles for each method. Students are then assigned to conduct experiments in the field to measure obstructed distances using these procedures.

Uploaded by

Enriquez Martinez May Ann
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
You are on page 1/ 4

PROCEDURE:

Obstacles to Chaining:

During measurements, it is impossible to set out all the chain lines in a

straightforward method because of a variety of obstacles to chaining and ranging in

the field.

Obstacles to measurement:

The obstacles which do not obstruct the ranging (view) like ponds, rivers are known

as Obstacles to Measurement.

Obstacles to alignment:

The obstacles which we cannot see across, i.e. both the chaining and ranging are

obstructed, e.g. houses, stacks, etc. are known as Obstacles to Alignment.

Obstacles to measurement:

First Method:

Let ABCD be a chain line obstructed by a pond (Fig 1). Let BC be the obstructed

length. Two offsets BE and CF of equal lengths are made at B and C and chaining is

done along EF to measure the distance EF.

Now the required obstructed length BC is equal to the measured distance EF.

Therefore, BC = EF

Second Method:

Let AB be the obstructed length across the river (Fig 2). AC is laid off, of any

convenient length, perpendicular to the required distance AB.

19

Now a perpendicular is laid off from C such that it meets the extended line of AB at

D.
Triangles ABC and ADC are similar triangles.

From the principle of similar triangles,

AB / AC = AC / AD

Therefore, obstructed length AB = AC2

/ AD

Third Method:

Let AB be a chain line obstructed by a river (Fig 3). A point I is assumed anywhere in

line with the required distance AB. A point H is taken in such a way that HJ = HI and

HK = HB.

Now a point L is established in line AH and at the same time in the line JK produced.

Triangles KHL and ABH are similar triangles and their corresponding sides are equal

to each other as the points K, B and I, J are equidistant either side from H.

Therefore, the obstructed length AB = KL

Obstacles to alignment:

First Method:

Let DE be the obstructed length across the building (Fig 4). A point C is assumed

arbitrarily. E and C are joined such that EC = CB. Now D and C are also joined such

that DC = CA.

Triangles CDE and CBA are similar triangles and their corresponding sides are equal

to each other as points BE and AD are equidistant either side from C.

20

Therefore, obstructed length DE = BA

Second Method:

Let DE be the obstructed length across the building (Fig 5). A point F is established at

equal distances from D and E at any convenient distance. Points H and G are
established such that FH = FG.

Triangles FDE and FHG are similar triangles.

From the principle of similar triangles,

DE / DF = HG / HF

Therefore, obstructed length DE = (HG X DF) / HF

CALCULATIONS:

RESULT:

Obstacles to measurement:

Obstructed length from First Method = m

Obstructed length from Second Method = m

Obstructed length from Third Method = m

Obstacles to alignment:

Obstructed length from First Method = m

21

Obstructed length from Second Method = m

PRELAB QUESTIONS:

1. What is obstacle to chaining?

2. What is obstacle to ranging?

3. What is the least count of metric chain?

4. What is indirect ranging and how it can be done?

LAB ASSIGNMNET:

You are required to conduct the experiment by adopting above procedure for a given

obstacle.

POSTLAB QUESTIONS:

1. How the offsets are taken in the field without cross staff?
2. What are the precautions are to be taken in indirect ranging?

3. What is obstacle to chaining and ranging both?

4. What is line ranger?

You might also like