Constraint criteria for adjustment of potential field surveys

In airorne gravity surveys, as well as in airborne magnetics and shipboard gravity and magnetics surveys, discrepancies between measurements on different tracks may exist at the intersections of those tracks. Advances in navigational systems, such as the implementation of the Global Positioning System, reduce discrepancies due to mislocation; but discrepancies from other sources remain. These misties should be removed before procedures such as contouring the data set or performing two-dimensional (2-D) analyses are performed. Various approaches have been used to remove misties, but the most reasonable is to estimate the most likely error and subsequently adjust the data. The procedure is to hypothesize the “shape” of the error along the tracks and then to find errors that minimize ∑Intersection[(observed1+error1)−(observed2+error2)]2 Error minimization has been carried out for various types of surveys with different error models (e.g., Zurflueh, 1968; Yarger et al., 1978, Sander and Mrazek, 1982). The general method is applicable to airborne gravity surveys but requires some changes from applications to other types of surveys. Based on techniques we have used for airborne gravity surveys, we propose modifications which should also be useful in applying the method to a wider class of adjustment problems.