Curvature and refraction corrections in levelling
Why long sights read too high, the 0.0785 d² and 0.0112 d² corrections, and the distance to the visible horizon.
Subject
Surveying
Levelling, traversing, curves and total station work.
Levelling: height of instrument vs rise and fall, with the checks
How to reduce a level book both ways, the arithmetic checks examiners love, and when each method is better.
Simple circular curves: elements and setting out by Rankine's method
Tangent length, curve length, external distance and long chord, and how deflection angles set out the curve with a theodolite.
Tacheometry: measuring distance with stadia hairs
How a theodolite with stadia hairs gives horizontal distance and elevation from a single staff reading, including inclined sights.
Closed traverse: latitudes, departures and Bowditch's rule
How to compute a traverse, find the closing error, and adjust it with the compass (Bowditch) rule.