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The anisotropic magnetoresistive (AMR) sensors provide an excellent means of measuring both linear and angular position and displacement in the earth's magnetic field. The electrical output of these sensors is proportional to the magnetic field strength along its sensitive axis. When such a sensor is spun around a horizontal plane starting from magnetic north, the output is a cosine function of the heading angle. Generally, a minimum of two sensors that are arranged mutually perpendicular would eliminate the ambiguity in electrical output with respect to heading direction. In this paper, based on cross effect estimation, the insensitive-axis cross-term of sensor A in HMC1002 is measured and a low power compass is designed. The results of experiment show that the accuracy of proposed compass is about 2° in horizontal position. The current consumption of proposed single sensitive-axis compass is about 20 mA, which is about 30% lower than that of formerly designed two sensitive-axis compass. It can be seen that proposed single sensitive-axis compass is effective.