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23. Ad nc d
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23.1 Varying curvature method
Although Minimum Curvature is now considered the indisputable industry standard for survey calculation, another method was developed in the early 1990s known as Varying Curvature. It turns out that the VC method produces very similar results to Minimum Curvature but has the advantage that it can be used to perform QC on whole surveys to check for poor consistency in the data.
Consider again the effect of a small increase in MD along a particular inclination and direction.
Figure 106: Measured depth error and the effect on North, East and TVD.
If we were to produce a set of graphs where the x axis is measured depth and the y axes were respectively cos(I), sin(I)cos(A) and sin(I)sin(A) then we can use the fact that the integrals of each would be the accumulated sums of TVD, Northing and Easting.
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