Apparatus and method for determining boring direction when boring underground

摘要

A guidance module for an underground horizontal boring assembly. The module determines the pitch angle of the boring tool independent of roll using a single accelerometer sensor. The accelerometer sensor has a single sensitive axis which is aligned parallel to, and preferably coaxial with, the longitudinal axis of the boring tool. The accelerometer sensor is calibrated to obtain a temperature offset and a gain compensating gain factor. Data samples are read from the accelerometer sensor while the boring tool is rotating. The temperature is read from the temperature sensor. The data samples from the accelerometer sensor and the temperature from the temperature sensor are transmitted to a processor. The processor applies simple average filtering to the accelerometer data samples to get an average result, and adjusts the average result for gain. The average result is adjusted for the temperature offset and for the gain compensating gain factor. The average result then can be adjusted for an optional roll angle offset. The pitch angle is determined either from a lookup table or from the arcsin value of the quantity of the average result minus the temperature offset divided by the gain compensating gain factor. <IMAGE>