THEODOLITE SURVEYING LESSON 8
TOPIC: LATITUDE
AND DEPARTURE OF LINE
•
The traverse is plotted on plan with
reference to YY1 and XX1
axes
•
Axis YY1 is parallel to the meridian and XX1 is perpendicular to the meridian
•
These lines are called as axes of
co-ordinates and point of intersection
is called origin
LATITUDE
AND DEPARTURE
Latitude:
When a line is measured
parallel to the meridian is called latitude i.e parallel to the YY1 axis (North
to South)
Departure:
When a line is measured perpendicular to the
meridian is called departure i.e parallel to the XX1 axis (East to West)
Latitude of Line OA = AA’
Departure of Line OA = AA”
Signs of latitude and departures are shown below,
depends on the direction they measure
•
Northing :
Latitude towards North ( +L )
•
Southing :
Latitude towards South ( -L )
•
Easting :
Departure towards East ( +D )
•
Westing :
Departure towards West ( -D )
Measurement of Latitude and Departure
•
Latitude of a line = L cos θ
•
Departure of a line =
L sin θ
Where :
L =
Length of a line
θ = Reduced
bearing of a line
The following table shows the signs of Latitude and
Departure
•
Consecutive
co-ordinates or Dependent co- ordinates
•
Independent
co-ordinates or Total co-ordinates
•
These co-ordinates
are used in
1.
Computing areas of
closed traverse
2.
Checking the field
measurement
ERROR OF CLOSURE
•
Errors in the field at the time of measuring
of lengths and angles will not allow the starting and ending point of the traverse to coincide. This is called as error
of closure or closing error
•
This can be minimized by checking instruments
and taking care of field work. However the errors can be checked
CHECK ON ERROR OF
CLOSURE
•
Total sum of interior angles = (2n-4) 90
degrees
n= number of sides of a traverse
•
The algebraic sum of all latitudes should be
equal to zero
•
The algebraic sum of all departures should be
equal to zero
CLICK HERE FOR LESSON 8
CLICK HERE FOR LESSON 9 (COMMING SOON)
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