Operator's guide
The two-stage algorithm rotates the N/S and E/W components of
the sensor being tested in small steps.
It measures first the amplitude similarity, and then the
coherence between this new N/S component and the reference
N/S component, for a number of rotation angles.
The error in the final calculation is around 2.5 °.
The peak of the coherence curve (upper graph) therefore
corresponds to the angle of rotation which best matched the
reference component. This angle is shown in the title bar,
together with an estimated error.
You should see a coherence curve which is smooth and
symmetrical. If the curve is distorted, either the surface data is
too noisy or the data selection is too short.
The lower graph shows the overall amplitude similarity of the
rotated signal. This provides an idea of the sign of the coherence
(since signals in perfect antiphase have a high coherence as well
as those in phase). If there are two peaks in the coherence graph,
the correct one is where the amplitude similarity is most
positive.
The sample plots show that the borehole instrument is installed
with its N/S axis at a bearing of –90 ° from true North.
13.The second window shows the result of applying the rotation to
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