Graphical Terrane Correction for Gravity Gradient Page: 12

12 GRAPHICAL TERRANE CORRECTION FOR GRAVITY GRADIENT
reference. The rest of the calculation on the chart, as shown in
Figure 4, is carried on as if it were necessary to calculate the effect
2U
of only this one octant. The final result both for bzbe and for
b2U
62 eis the gradient due to that irregularity of topography. It
is an effect and not a correction. To obtain the terrane correction
it is necessary to change the sign of the effect and add or subtract it.
If this had been an actual station, the effect of the north, east, and
southeast octants would have been obtained in the same manner.
The effect within the 5-meter zone and in the south, southwest, west,
and northwest octants would be obtained by the ordinary Eetv)s or
Schweydar methods. The sum of all these effects is the effect that is
subtracted from the observed value of the gradient.
0