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 = -0.01*4 = 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 is ’ from the assigned start
Don’t assign start point to 0+00

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