9. Engineering and Construction Surveying
Engineering and Construction Surveying
This domain tests setting out, control networks, curves, earthworks and as-built verification. Expect tolerance thinking, reference systems and the link between design coordinates and site marks.
Core rules
- Establish a stable control network before setting out; design coordinates must use the same datum and projection as the control.
- Setting out transfers design points to ground with offsets, total station or GNSS, then checks by independent measurement.
- Circular curve tangent length T = R tan(D/2); curve length L = R x D in radians.
- Earthwork volumes require cross-sections or a DEM and a consistent datum.
- As-built surveys compare constructed works with design and record deviations against tolerance.
Worked example
A circular curve has radius R = 200 m and deflection angle D = 40 degrees. Tangent length T = 200 tan(20 degrees) = 200 x 0.36397 = 72.79 m. Curve length L = 200 x 40 x pi/180 = 139.63 m. Set the tangent points at 72.79 m from the intersection point along each tangent. A common error is using the chord for the tangent length.
Traps
Setting out from uncontrolled points; ignoring projection scale factor; using the wrong prism constant; failing to check a backsight; reporting as-built coordinates without tolerance context.