Some methods deriving the anomalies of geomagnetic components from observed values of the anomaly of total force are proposed by one (N.F.) of the writers [1]. Between the anomaly of total force and the geomagnetic potential at grid points in a plane the following equation holds.
2πs F
0/Z
0 ΔF(
i,
j)=∞Σμ=-∞∞Σν=-∞Φ(μ, ν)W(
i+μ,
j+ν),
where s is the spacing of grid points and Φ(μ, υ) is the weighting function given by (19). The anomalies of geomagnetic components are obtained from (7), (8) and (9). The following assumptions are involved in this method.1) W-surface considered as the group of small planes.2) W=O outside the area of grid points.3) The normal values Xo, Yo, Zo and Fo are approximately known and the approximation shown in (7) is adopted. In the actual procedure, the density of grid points is determined considering the pattern of ΔF observed. The surveying area is divided into blocks with suitable size and these blocks are overlapped to some extent. From the results (Figs 2.-4) of computation using the model combined two dipoles, it is clarified that the anomalies of geomagnetic components can be computed in almost the same accuracy of dF observed. In the southern part of Kanto district where the total force is only measured in the aeromagnetic survey (Fig. 5), the anomalies of geomagnetic components are obtained as shown in Fig. 6.
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