Figure F4. Hole 1203A magnetic logs from the orientated Göttingen Borehole Magnetometer (GBM) and Schlumberger's General Purpose Inclinometry Tool (GPIT). (A) Intensity (F) and (B) inclination (Inc) by GBM (blue) and FMS-sonic GPIT (red). Note the good match at the meter scale between these logs. C. Comparison between the direct GBM declination (Dec) (blue) and deduced declination (dec) using the proposed algorithm (4-m-wide cosine filter, light green) from GBM raw magnetic logs (Fx, Fy, and Fz). Due to the filtering operating, high-frequency fluctuations (<10°) in the declination are smoothed without affecting the indirect computation of the GBM rotation from its raw magnetic parameters. D. Comparison of the declination records deduced from the GPIT raw magnetic logs using our algorithm (4-m-wide cosine filter, dark green) and the Schlumberger algorithm (2.4-m-wide Hamming filter, orange).

Figure F4. Hole 1203A magnetic logs from the orientated Göttingen Borehole Magnetometer (GBM) and Schlumberger's General Purpose Inclinometry Tool (GPIT). (A) Intensity (F) and (B) inclination (Inc) by GBM (blue) and FMS-sonic GPIT (red). Note the good match at the meter scale between these logs. C. Comparison between the direct GBM declination (Dec) (blue) and deduced declination (dec) using the proposed algorithm (4-m-wide cosine filter, light green) from GBM raw magnetic logs (Fx, Fy, and Fz). Due to the filtering operating, high-frequency fluctuations (<10°) in the declination are smoothed without affecting the indirect computation of the GBM rotation from its raw magnetic parameters. D. Comparison of the declination records deduced from the GPIT raw magnetic logs using our algorithm (4-m-wide cosine filter, dark green) and the Schlumberger algorithm (2.4-m-wide Hamming filter, orange).