Chapter 11

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
• 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
S3815E 315.62
C
N6854E 502.43
B
5
Traversing Methods

• Interior Angle Traverse
• Find direction of one side from N
• Occupy each station in turn
• Measure interior angles
• Measure distances

6
Traversing Methods

• When all interior angles are known
• Check angular misclosure
• Total (n-2)(180)
• n 5
• Total (5-2)(180) 540

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

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

10
Offsets

• Establish parallel lines
• Fig 11-5, pg 208
• Turn 90 from line
• Measure equal distances
• Find Intersection
• Determine angle by measurement
• Fig 11-6, page 209
• ? 2arcsin(Chord/2Fence)

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