Horizontal Curves
 Basic Properties Of
    Horizontal Curves
 Location Of Tangent
    Points
 Setting Out
 Offsets From The Tangent
 Offsets From The Chord
 Deflection Angles
 Deflection Distances
 Quartering
 Coordinates
 Transitions Curves

Setting Out - Coordinates

A very common method for establishing the centreline of curves on the ground is to compute the coordinates of the peg positions (using any of the available methods covered previously), and to radiate to these coordinates from survey control stations. This has many advantages, especially when electronic tacheometers are used. The layout is quick, the instrument can be located away from the main works area, and precomputed coordinates can be stored in the memory of many modern instruments and data recorders eliminating the need for on site calculations. Most major engineering constructions are now fully coodinated and all site layout is performed using this method.

An appropriate method is used to calculate the position of the pegs, for example using the deflection angle method to determine bearings to each peg from the tangent point and using the chord distances to calculate change in coordinates. Once the coordinates for each peg have been calculated, the bearing and distance from the control points to the pegs are then calculated and used to establish the location of the pegs on the ground. Once again, another method would need to be used to check the location of each peg.