surveying iii (topographic and geodetic surveys) - Modern Prepper

The correction to be applied to the relative deflection of the vertical at the initial pointis determined by the mean of the differences between the absolute gravimetric andrelative astro-geodetic deflection components (Figure 1-20).Figure 1-20. Gravimetric Datum Orientation Due to this correction at the origin, the relative deflections of the vertical componentsat the other Laplace stations are corrected. The relation between the corrections at theinitial point and those of the other Laplace stations can then be computed. Readjusting the triangulation stations of the net, by holding fixed the correctedLaplace stations, provides the correct position of the net.(b) Before such a gravimetric adjustment is possible, a general study of the earth's gravityfield is required. A detailed study of the gravity field is required in the area of the points where thegravimetric deflection of the vertical is to be computed.1-31 EN0593