Chapter 8

1
Chapter 8 Leveling, Cont.

• Adjustment of Circuits
• Precise Leveling
• Profile Leveling
• Cross-sectioning

2
Adjustment of Circuits

• Misclosure
• Difference between determined and known elevation
• Error adjusted by proportioning misclosure
• Proportion based on sources of errors
• Distance from start better
• Number of set-ups

3
Adjustments are Cumulative

• Given Misclosure 0.05 over 5 set-ups
• Assume each set-up contributed equally
• Adjustment for each set-up -Misclosure/No. of
  Setups -0.05/5 -0.01
• Adjustment to the 4th point -0.014 0.04

4
Precise Leveling

• Shade the level
• Three-wire leveling
• Precise Level Rods
• Double-rodded Lines

5
Profile Leveling

• Used in route surveys
• Route definite beginning and end points
• Follows a baseline or center line
• Determine terrain along a center-line
• Tells you nothing about cross-section
• Location reference Stationing
• Assign an arbitrary starting point
• Every 100 is one station
• Sta 653.25 is 653.25 from the assigned start
• Dont assign start point to 000

6
Profile Leveling

• Elevations needed every 100, 50 or 25
• Rough elevations nearest 1/10th
• Too many set-ups if each point is a BM
• Take intermediate shots IFS
• Find TP at acceptable limits of sight

7
Profile Leveling
8
Profile Drawing

• Scales not the same V H
• Fit a smooth curve
• Assume no intermediate shots means straight
  grade between

9
Cross-sectioning

• Determines elevations along a line perpendicular
  to centerline
• Prism glass
• Wing-ding
• Shots at pre-determined distances
• Rod-person chooses additional points

10
Cross-sectioning Notes

• Often laid out bottom to top
• Centerline appears as IFS
• All other shots shown on grid
• Reading/Distance, e.g. 3.2/16
• Rod Reading 3.2
• Rod located 16 right or left
• Elevations calculated from last HI

11
Cross-sectioning Notes
12
Borrow-Pit Cross Sections

• Lay out a grid
• Every 25, 50, etc.
• Use lath to find grid points
• Label A1, B3, etc.
• Shots at grid points are IFS

13
Borrow Pit Cross Sections