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Appendix D:Road layout: traditional method for setting-out main pointsWhen the setting-out stations have been ‘proved’ on site, the site engineer can calculate the bearings and distancesof the main points and centre-lines of roads 34 and 31 in the layout. This is facilitated by drawing skeleton layouts asshown opposite. The top layout shows the centre-lines and (some) coordinates of centre points and intersectionpoints. Tangent points are 34/1a, 34/1b, etc. The lower layout is a basis for recording calculated bearings anddistances for use on site.The calculations should be done in the office.Starting from Station 8, to fix the base point of the hammer head on road 34 (0/34), coordinates are converted intobearings and distances thus:Station Eastings Northings0/34 9372.500 3999.750Station 8 9353.936 3958.294Partial coordinates 8 to 0/34 +18.564 +41.456α = whole circle bearing = tan −1 (18.564/41.456) = 24° 07' 22"The distance from 8 to 0/34 =√(18.5642+41.4562) = 45.423 mNote: The calculation of ground and bearings is facilitated by the use of polar coordinates on a suitable calculator orin a spreadsheet but the above method would provide a suitable cross-check.Similar calculations are repeated along the main line of roads 34 and 31. To ensure the setting-out ‘closes’, checkbearings and distances from alternative stations are added.The setting engineer can now start setting-out the main points on site using colour coded pegs as describedpreviously. Setting up the instrument over station 8, fix bearing 289° 52' 32" and sight on station 13. Then readingbearing 24° 07' 22", measure 45.42 m, taking into account slope. This will determine point 0/34. This sequence isrepeated along the main lines of roads 34 and 31 starting at 0/34. Check bearings are taken from station 13 andstation 10 to 0/31.CIRIA C709127