An especially calibrated stereographic net is described and displayed which is the foundation for the computer assembly. A transparent overlay disc printed with suitable reference marks and a central fastener pin complete the computer. Input and temporary data storage are accomplished by using a sharpened grease pencil to plot data on the transparent disc.

Two apparent dips relative to the bore axis-normal produce a pole plot of the uncorrected dip. Tool orientation, inclination and drift corrections are made by following a simple three-step technique on the overlay. Readout of true dip and direction of dip corrected for magnetic declination is automatic. The operation from raw data to finished results requires less than one minute.

Dips up to 89°, with or without hole drift angles up to 89°, can be accurately handled. Overturned bedding relative to the bore is readily indicated.

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