chapter 8 – leveling, cont. adjustment of circuits precise leveling profile leveling...

Chapter 8 – Leveling, Cont. Adjustment of Circuits Precise Leveling Profile Leveling Cross-sectioning

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Chapter 8 – Leveling, Cont. Adjustment of Circuits Precise Leveling Profile Leveling Cross-sectioning

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

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’

Precise Leveling

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

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 6+53.25 is 653.25’ from the assigned

start Don’t assign start point to 0+00

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

Profile Leveling

Profile Drawing Scales not the same: V & H Fit a smooth curve Assume: no intermediate shots means

straight grade between

Cross-sectioning Determines elevations along a line

perpendicular to centerline Prism glass Wing-ding

Shots at pre-determined distances Rod-person chooses additional


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

Cross-sectioning Notes

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

Borrow Pit Cross Sections