Gravity high side: At a certain depth position on the borehole curve, when the plumb line crosses the well axis, the side where the plumb line enters is called the gravity high side of the wellbore.
Inclination angle: The inclination angle is the angle between the axis of the drilling tool and the plumb line. It reflects the inclination of the drilling tool and the vertical direction to the center of the earth. At a depth position on the wellbore curve, the angle between the tangential direction of the well axis and the direction of the plumb line is called the wellbore dip at that depth, also known as the well deviation angle (or simply well deviation).
Azimuth angle: The azimuth angle is the angle between the calibration direction and the horizontal projection direction of the drill tool axis, which reflects the direction of the drill tool movement in the horizontal plane. When the calibration direction is the geographic meridian, it is called the true borehole azimuth; when the calibration direction is the magnetic north direction, it is the borehole magnetic azimuth.
Tool facing angle: The tool facing angle refers to the plane perpendicular to the axis of the drilling tool (hole plane). The angle between the plane formed by the elbow joint and the plumb line is called the high-side tool face orientation or high-side Tool face angle. Take the gravity high side as 0° and clockwise as positive to calculate the high side tool face angle. The angle between the horizontal projection of the plane formed by the elbow joint and the geomagnetic meridian is called the magnetic tool face orientation or the magnetic tool face angle. Calculate the magnetic tool face angle with the tool face pointing to the magnetic north pole as 0° and clockwise as the positive.
If you want to get more details about FOG Continuous Gyro Tool ,pls visit https://www.ericcointernational.com/drilling-and-logging-system/north-seeking-gyro/er-fiw03-continuous-fog-north-seeking-gyro.html