shown in fig4 the rate gyro therefore provides an reading of the azimuth 67 of the well path 10 u2032 referenced to a fixed direction such as true north by combining the output of the gyro sensitive axes g y g x and the accelerometer outputs a x a y the well bore direction inclination and tool face highside can be determined depth is incorporated from the amount of wireline 10 deployed from the drum 12 to lower the probe 20 within the borehole 10 combining a series of survey stations downhole through a calculation method such as minimum curvature yields wellbore trajectory path 10 u2032 the continuous survey mode is based on measuring relative instrument rotations while the probe 20 is continuously traversing through the borehole 10 after taking a stationary reference heading measurement in the gyrocompassing mode new modeling procedures allow computation of probe azimuth and inclination changes da dt and di dt respectively about the highside hs and highside right hsr directions where the hsr direction is at right angles with respect to the hs direction this is accomplished by mathematically projecting da dt and di dt into the gyro sensitive axis plane gy gx as shown in fig5 in order to calculate the actual wellbore path the rate of rotation about hs and hsr are integrated over time yielding wellbore heading and inclination changes from the previously described reference procedure in conjunction with depth which is derived by continuously.