Measurements made by a near-bit magnetic sensor on a bottomhole assembly are used to determine the azimuth of the BHA. The sensor may be uncalibrated. The measurement may include a cross-axial component of the magnetic field. The method may include estimating the axial component of the near-bit magnetic field using the measurement. The method may include using the estimated azimuth of the BHA for controlling a direction of drilling. The method may include estimating the component Hxy. The method may include correcting the estimated axial component using an offset between a gravitational toolface and a magnetic toolface.