Download - Engineering Surveyor

Appendix D:Road layout: traditional method Proving setting-out stationsThe procedure for proving the coordinates of setting-out stations is given in the main text. An example is given belowusing the road layout illustrated previously.Calculate ground distanceFrom coordinates of stations 8 and 13, for example:Calculated ground distance 8 to 13 =Check ground distanceStation Eastings NorthingsStation 13 9180.659 4020.936Station 8 9353.936 3958.294Partial coordinates 8 to 13 −173.277 +62.642= 184.252 mAssume that measured and calculated ground distances between stations 8 and 13 agree within 20 mm.Therefore Stations 8 and 13 may define baseline.Calculate relative bearingsReferring to figure opposite, for stations 8 and 13:tan α = (δ eastings/ δ northings) = 173.277/62.642, α = 70° 07' 28"Therefore, whole circle bearing = 289° 52' 32"Repeat for Stations 10 and 8Station Eastings NorthingsStation 10 9290.208 4152.296Station 8 9353.936 3958.294Partial coordinates 8 to 10 −63.728 +194.002tan β = 63.728/194.002, β =18° 11' 06", WCB = 341° 48' 54"Repeat for Stations 5 and 8, γ = whole circle bearing = 17° 50' 45"Note: The calculation of ground distance and bearing is facilitated by the use of polar coordinates on a suitablecalculator or in a spreadsheet but the above method would provide a suitable cross-check.Check relative bearings set up instrument on station 8 set upper plate to whole circle bearing for station 13 from station 8 align instrument on station 13 and lock lower plate release upper plate and observe whole circle bearings when aligned on stations 10 and 5 in turn.Repeat procedure on opposite face. Check that the error between mean observed and calculated whole circlebearings is acceptable.CIRIA C709125