Compass

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Compass Transit
Civl 235 Plane Surveying
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Contact Information
Max.T.Sanches mts_at_igen.ubc.ca Subject Re
Civil 235
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Outline
The Compass North Bearings The Circle
The Transit Optics The Traverse
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The Compass
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The Compass
Compass needle always points North?
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North
Magnetic North
True North
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Magnetic North
Magnetic North
True North Declination
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Other Norths
Local
Grid
N
N
Y
X
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Bearings
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The Circle
Measured Clockwise From North
NNE
3600000 per Circle 900000 per
Quadrant -- 400 Grads per Circle 100 Grads per
Quadrant -- 6400 Mils per Circle 1600 Mils per
Quadrant
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360 per Circle 60 per 1 60 per 1 Eg 189
22 10
At 1km 1 17.5m 1 0.3m 1 0.005m
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The Transit
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The Transit
0
Pt. A
VA
0
HA
Pt. 1
Transit is used to measure Horizontal and
Vertical angles from the transit centre to a
target.
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Transit Classes
Wild Heerbrugg Transits Type Graduation Mag Range
Weight Uses T1A 20 28x 30
km 4.8 kg General T16 1 28x 30 km 4.5
kg General T2 1 28x 40 km 5.6
kg Control T3 0.2 40x 90 km 11
kg Geodetic T4 0.1 64x 60 kg Geodetic
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Optics
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Errors
Physical Errors Human Errors
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Physical Errors
aR
Pt. AR
aL
Pt. A
Pt. 1
Pt. AL
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Physical Errors
aR
Pt. AR
aL
Pt. A
Pt. 1
Pt. AL
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Physical Errors
aR
Pt. AR
aL
Pt. A
Pt. 1
Pt. AL
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Physical Errors
aR
Pt. AR
aL
Pt. A
Pt. 1
Pt. AL
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Traverse Math
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The Traverse
Pt. B
Known Pts 0,1,2,3 Bearings 1-0, 2-3
Unknown Pts A,B,C Bearings 1-A, A-B, B-C,
C-2
Measured Angles a1, aA, aB, aC, a2
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A Traverse Leg
N
(XA,YA)
dY
dX
(X1,Y1)
Known Pts 0,1 Bearings 1-0
Unknown Pt. A, Bearing 1-A,
Measured Angle a1 Distance 1-A
Calculate Bearing 1-A Pt. A
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The Traverse
Closed Loop Traverse

• Notes
• The sum of the internal
• angles SB 180(N-2)
• (where N is the number
• of legs.)
• Must start and end on
• same point.
• Minimum requirements
• - One known Point (x,y)
• - One known Bearing.
• Or
• - Two known points

Pt. 2
Pt. C
aC
a2
ß1-2
aB
Pt. B
a1
Pt. 1
aA
Pt. A
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The Traverse
Closed Traverse
Pt. 3
ß2-3

• Notes
• Minimum requirements
• - Start and End Known

Pt. 0
a2
Pt. 2
Pt. A
ß1-0
aA
a1
aC
Pt. 1
aB
Pt. C
Pt. B
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The Traverse
Open Traverse

• Notes
• No requirements
• No error checking

Pt. 0
Pt. A
ß1-0
aA
a1
Pt. 1
aB
Pt. C
Pt. B
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The Traverse
Traverse By Deflections
Pt. 0
Pt. A

• Notes
• Right Left deflections.
• Different Calcs Right Left
• Easy in the office.
• Difficult in the field.
• Used for Line Traverse
• (e.g., Roads, Power lines, etc.)

ß1-0
d1L
d1
Pt. 1
Known Pts 0,1,2,3 Bearings 1-0, 2-3
Unknown Pts A,B,C Bearings 1-A, A-B, B-C,
C-2
Measured Deflections d1 or d1L
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Recommended Text Elementary Surveying, Fryer,
Elfick, Brinker Wolf. Harper Row
Publishers. Survey Theory and Practice, Davis,
Foote, Anderson Mikhail McGaw-Hill
Publishers. Introductory Surveying, Schaums
outlines.