EBC 2102: ENGINEERING SURVEY I (THEORY): 24 CONTACT HOURS
LECTURE SESSIONS
Session Three:
3.1 Session Objectives:
At the end of the lesson the students should be able to:-
Explain chain survey procedure
Carry out chain surveying around obstacles
Adjust for Chain survey errors
3.2Explain chain survey procedure
3.2.1 Suitability of chain surveying
The area of surveying is completely small.
The ground is fairly small.
The area is open
3.2.2Procedure of Chain surveying
Reconnaissance survey
Making of stations
Preparation of reference sketches
Running of a survey line
Locate the position of building with reference to survey line
3.2.2.1Reconnaissance survey
It is always useful and often absolutely necessary for the survey to make a preliminary inspection of the area
before commencing his actual detailed survey, for the purpose of fixing the survey stations and forming a general
,plan for the network of the chain lines. Such preliminary inspection of the area is generally known as
reconnaissance or reconnoiter.
On arriving at the ground the surveyor should, therefore, walk over the entire area to examine the ground to decide
upon the best layout of the chain lines.
During reconnaissance, the surveyor should ensure that the survey stations are intervisible, there is no difficulty in
chaining and the angles of the chain triangle are not acute.
3.2.2.2Marking Stations
On completion of successful reconnaissance, the survey stations should mark in such a way that they easily
discover during the progress of the survey even after some time, if necessary, to revise a faulty work.
In soft ground, wooden pegs are driven, leaving a small portion projected above the ground.
In case of roads or hard surface ground, nails or spikes may be driven flush with the pavement.
3.2.2.3Reference sketches
A brief description of each survey station gives and reference sketches drawn in the field book.
The sketch, showing a least three measurements to permanent and definite points such as the gates, pillars, light
posts, corners of the building, etc. known as a reference or location sketch.
3.2.2.4Running survey lines
So on completion of preliminary work, the survey lines ar earn as detailed below
The ranging is done between the end stations of the bare line.
The chain stretched in the true alignment keeping one end of the chain at the starting station.
As the arrow is fixed at the other end of the chain and the chain is kept laying on the ground.
The surveyor walks along the chain line and takes offsets to the adjacent objects on the right side and left side
as the case may.
The chainages on the chain line and the offsets record in the field book.
, So the process of chaining and offsetting is repeated until the end of the baseline is reached.
Other lines are similarly completed.
3.2.2.5 Located the position of building with reference to survey lines
The name or number of the chain line.
Name or number of the survey station.
The symbol denoting the station mark.
The Direction of surveying off form or ending at the station
3.2.3 Chain survey framework
When the surveyor is on the field to begin surveying he should first carry out a reconnaissance ( pre
visit to asses practical issues on the field)
Among other things the surveyor should:
Walk over the area to be surveyed to get the general view of the area.
Draw the sketch of the area
Make notes on the boundaries, obstacles likely to be encountered and other physical features
Note the positions to lay lines particularly the longest line called the back bone
Mark the stations with pegs or iron pins
Principles of selecting chain lines and marking stations
, As already mentioned the principles of survey require that the survey lines be arranged so that the area can be
plotted easily. To achieve these, the following factors are used:
The survey lines should be as few as possible and such as to form a sound geometrical framework
The triangles formed should be well conditioned i.e. the apex angles of the triangles should be
between 30▫ and 150▫
There should be an adequate number of the check lines which should be ideally used as chain lines to pick
the data details.
The offsets used should be kept as short as possible especially those to important features
Lines to lie over the more level ground
Lines along the roads with much traffic should be kept to one side
Obstacles should be avoided when laying lines
The chain lines to be kept close to the details
Lines used in the chain surveying
Offsets: These are lines which are at right angles to the chain lines to the detail (feature)
Chain lines are lines between the survey pints
Base line is the longest line on the lines framework
Check lines are chain lines which are positioned such that they can also be used check the survey accuracy at
the time of plotting
Tie lines are lines drawn at any angle from the chain line to the feature. The intersection of the tie lines
LECTURE SESSIONS
Session Three:
3.1 Session Objectives:
At the end of the lesson the students should be able to:-
Explain chain survey procedure
Carry out chain surveying around obstacles
Adjust for Chain survey errors
3.2Explain chain survey procedure
3.2.1 Suitability of chain surveying
The area of surveying is completely small.
The ground is fairly small.
The area is open
3.2.2Procedure of Chain surveying
Reconnaissance survey
Making of stations
Preparation of reference sketches
Running of a survey line
Locate the position of building with reference to survey line
3.2.2.1Reconnaissance survey
It is always useful and often absolutely necessary for the survey to make a preliminary inspection of the area
before commencing his actual detailed survey, for the purpose of fixing the survey stations and forming a general
,plan for the network of the chain lines. Such preliminary inspection of the area is generally known as
reconnaissance or reconnoiter.
On arriving at the ground the surveyor should, therefore, walk over the entire area to examine the ground to decide
upon the best layout of the chain lines.
During reconnaissance, the surveyor should ensure that the survey stations are intervisible, there is no difficulty in
chaining and the angles of the chain triangle are not acute.
3.2.2.2Marking Stations
On completion of successful reconnaissance, the survey stations should mark in such a way that they easily
discover during the progress of the survey even after some time, if necessary, to revise a faulty work.
In soft ground, wooden pegs are driven, leaving a small portion projected above the ground.
In case of roads or hard surface ground, nails or spikes may be driven flush with the pavement.
3.2.2.3Reference sketches
A brief description of each survey station gives and reference sketches drawn in the field book.
The sketch, showing a least three measurements to permanent and definite points such as the gates, pillars, light
posts, corners of the building, etc. known as a reference or location sketch.
3.2.2.4Running survey lines
So on completion of preliminary work, the survey lines ar earn as detailed below
The ranging is done between the end stations of the bare line.
The chain stretched in the true alignment keeping one end of the chain at the starting station.
As the arrow is fixed at the other end of the chain and the chain is kept laying on the ground.
The surveyor walks along the chain line and takes offsets to the adjacent objects on the right side and left side
as the case may.
The chainages on the chain line and the offsets record in the field book.
, So the process of chaining and offsetting is repeated until the end of the baseline is reached.
Other lines are similarly completed.
3.2.2.5 Located the position of building with reference to survey lines
The name or number of the chain line.
Name or number of the survey station.
The symbol denoting the station mark.
The Direction of surveying off form or ending at the station
3.2.3 Chain survey framework
When the surveyor is on the field to begin surveying he should first carry out a reconnaissance ( pre
visit to asses practical issues on the field)
Among other things the surveyor should:
Walk over the area to be surveyed to get the general view of the area.
Draw the sketch of the area
Make notes on the boundaries, obstacles likely to be encountered and other physical features
Note the positions to lay lines particularly the longest line called the back bone
Mark the stations with pegs or iron pins
Principles of selecting chain lines and marking stations
, As already mentioned the principles of survey require that the survey lines be arranged so that the area can be
plotted easily. To achieve these, the following factors are used:
The survey lines should be as few as possible and such as to form a sound geometrical framework
The triangles formed should be well conditioned i.e. the apex angles of the triangles should be
between 30▫ and 150▫
There should be an adequate number of the check lines which should be ideally used as chain lines to pick
the data details.
The offsets used should be kept as short as possible especially those to important features
Lines to lie over the more level ground
Lines along the roads with much traffic should be kept to one side
Obstacles should be avoided when laying lines
The chain lines to be kept close to the details
Lines used in the chain surveying
Offsets: These are lines which are at right angles to the chain lines to the detail (feature)
Chain lines are lines between the survey pints
Base line is the longest line on the lines framework
Check lines are chain lines which are positioned such that they can also be used check the survey accuracy at
the time of plotting
Tie lines are lines drawn at any angle from the chain line to the feature. The intersection of the tie lines
