| CPC G01C 25/005 (2013.01) [E21B 47/024 (2013.01)] | 9 Claims |
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1. A method comprising:
calibrating sensors within a sensor section of a drilling tool,
whereby the drilling tool follows a drilling trajectory along a Z-axis,
whereby the calibration of the sensor section occurs downhole and in-situ within the drilling tool,
whereby the sensor section includes sensors sensitive to rotation along the Z-axis including one or multiple angular rate sensors, one or multiple magnetometers sensitive to magnetic fields perpendicular to the Z-axis, and, optionally, one or multiple accelerometers,
wherein the calibration includes calibrating an offset error of one angular rate sensor, comprising:
rotating the sensor section along ts Z-axis at two pre-determined angular rates and directions in two phases, independently of the rotation rate of the drilling tool, wherein the two pre-determined angular rates are rotation rates with identical absolute values and the two pre-determined directions are opposite rotation directions,
recording an actual waveform signal of the magnetometers during each of the two phases,
calculating an actual angular rate and an actual direction for each of the two phases using the actual waveform signal of the magnetometers, and
comparing the actual angular rate to the pre-determined angular rate in each of the two phases.
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