Tools usually do not move up the well bore with a fixed velocity. Excess movements due to friction, sticking, rig-heave and cable movement all influence a tool’s actual speed within a well. As most dipmeter and borehole data are acquired in time rather than by depth we need to know this tool movement to place the data at a correct depth point. Using cable speed and doubly integrated acceleration data, all in conjunction with suitable filters, it is possible to determine a tools velocity and its position at any given time. This allows the derivation of a shift required to place the data at their correct positions.
See also accelerometer, speed button and stick and pull.