SURV1200 Lecture Notes - Lecture 4: Grid North, Theodolite, True North
2 Jun 2018
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4.Bearings
North- True north, magnetic north, grid north
Azimuth-Point to "North", set the horizontal Circle Reading (HCR) = 0, and then turn to a target
and read the bearings DON’T DO
INSTEAD-start using an Azimuth Line which is a line with a known bearing.
Bearings
1.clockwise from North
2.Values between 0 and 360
3.If Values are > 360, subtract 360
4.If values are <0 add 360
5.βBA = βAB +- 180 (Forward Reverse)
6.βAC=βAB + αBAC (Clockwise)
7.βAB = βAC - αCAB (anti-clockwise)
Distances
We need to know the vertical and horizontal components. Using vertical angles, we can reduce
the slope distance to a horizontal distance.
Where θ is the vertical angle
Where RL= Reduced Level, HT= Height of Target, HI= Height of Instrument
Coordinates
Coordinated are of the format
2D (E, N) or (X, Y)
3D (E, N, Ht) or (X, Y, Z)
A
B
C
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