Explain the meaning of the term ‘grid convergence'. Show how this factor has to be taken into account when running long survey lines by theodolite. From a point A in latitude 53?N, longitude 2?W, a line is run at right angles to the initial meridian for a distance of 31 680 m in a westernly direction to point B. Calculate the true bearing of the line at B, and the longitude of that point. Calculate also the bearing and distance from B of a point on the meridian of B at the same latitude as the starting point A. The radius of the Earth may be taken as 6273 km