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

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

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

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

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 = 315.62’ 107°9’ BA bears N38°15’ W, Az = 321°45’ 321°45’ + 107°9’ - 360° = 68°54’ BC bears N 68°54’ E

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

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

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

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

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)]

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