This tool provides accurate, continuous measurements of borehole inclination and heading (Azimuth). These are output directly as log traces or may be processed further to produce a three-dimensional plot of borehole position, borehole drift and true vertical depth. The tool includes a tri-axial magnetometer to deduce the probe bearing relative to magnetic North and three accelerometers to measure inclination. The outputs from the transducers are processed by a downhole microprocessor to give final borehole inclination and azimuth data in real time. The operation of the probe is limited in steel casing or in the presence of magnetic minerals which affect the magnetometer. Under such conditions, only borehole inclination (without directional information) can be logged.
