fig5 and overlay it on the video display screen to quickly determine the true orientation of a particular section of the sidewall image shown on the video screen the center of the compass 102 acetate overlay is matched up with the dot 67 for the depth the north arrow 104 is aligned with the north gyroscope dot 66 on the display 14 now the directional bearings of the entire wall can readily be determined the two sections comprising the video tool the second housing having the electronic components and gyroscope and the camera first housing are coupled sections having interlocking pin 51 and hole 31 so that when they are connected together the gyroscope will always be in the same orientation as the camera is the cable head 3 which connects to the upper section of the tool also has an interlocking pin 5 with the upper section hole 29 so that all three parts can only be assembled or coupled in a preset configuration when a job is initially begun the gyroscope must be 34 zeroed 34 in to a fixed directional reference which is normally the true north this is accomplished by having as assistant standing several hundred feet away with a survey sight line pointing to the true north and by means of a tripod or transit the true north is accurately determined in turn the gyroscope 32 which is caged in the housing 30 is adjusted so that its reference point 66 is set to the true north the gyroscope in its uncaged position will always.