1. Chapter 11 – Angles Errors and Mistakes Methods of Traversing
Techniques for:
Intersections
Offsets
Prolonging and establishing lines
Bypassing obstructions

2. Errors/Mistakes Errors Not level/not centered Pointing errors Settling
Wind
Plumb bob too high
Pointing errors
Target size
Heat waves
Settling
Imperfect vernier readings

3. Errors/Mistakes Mistakes Improper/insufficient leveling
Recording wrong numbers
Transpose
Wrong vernier/circle
Improper sighting
Using wrong motion
Wrong tangent screw
Motion not locked

4. Traversing
Traverse: a series of points connected by lines of known direction and length E D A
S38°15’E
315.62’
N68°54’E
502.43’ C B

5. Traversing Methods Interior Angle Traverse
Find direction of one side from N
Occupy each station in turn
Measure interior angles
Measure distances A B C D E
141° 45’
SE: 180° - 141° 45’ = 38°15’ AB bears S 38°15’ E
86°26’
Dist AB = ’
107°9’
BA bears N38°15’ W, Az = 321°45’ 321°45’ + 107°9’ - 360° = 68°54’ BC bears N 68°54’ E

6. Traversing Methods When all interior angles are known:
Check angular misclosure
Total = (n-2)(180°)
n = 5
Total = (5-2)(180°) = 540° A B C D E

7. Traversing Methods Deflection angle traverse
Usually used for route surveys
Deflection from previous line
Define direction for initial line
Measure to point of change
Prolong line, turn L or R
113° 12’ C A B
24° 53’ R D
31° 40’ L

8. Prolonging Lines Backsight, Plunge scope May be some error
Turn to Backsight
Plunge again
Line is halfway between

9. Traversing Methods Radiation Occupy central point Turn angles
Shoot Distances A B C D E

10. Offsets Establish parallel lines Determine angle by measurement
Fig 11-5, pg 208
Turn 90° from line
Measure equal distances
Find Intersection
Determine angle by measurement
Fig 11-6, page 209
 = 2[arcsin(Chord/2*Fence)]

11. Establishing Lines Balancing In Random Lines
Points along a line – Fig 11-9, pg 211
Establish intermediate points B’, C’ on AE
Similar triangles
Random Points – Fig 11-10, pg 211
Use consistent deflection angle
Angle at A = (Defl Angle at B)/2