Abstract: A static non-swinging device for determining the course on board a vehicle comprising a magnetometer having three axes for determining the components of the earth's magnetic field along three axes connected to the vehicle, a vertical gyroscope and a computer for calculating the direction with respect to the vehicle of the horizontal component of the earth's magnetic field, wherein said magnetometer comprises on each axis a single coil having a saturable core controlled in such manner as to furnish a d-c voltage which is proportional to the component of the magnetic field along said axis.