Method of determining the location of a navigational magnetic field sensor in a vehicle

Claim 1

Method permitting relatively unskilled installers to install in a vehicle, a navigational magnetic field sensor (11) in a location where saturation of said sensor and consequent erroneous navigation indications are avoided, in which the entire magnetic field to which the field sensor is subjected is composed of the geomagnetic field and, when present, a stray or disturbance field resulting from at least one of permanent magnetic characteristics of said vehicle and transient magnetic fields emanating from energized equipment in said vehicle, the magnetic field sensor is responsive to the entire magnetic field permeating the sensor, navigation of the vehicle is guided by reference to the geomagnetic field forming at least a component of the entire field, a vector diagram of a measured magnetic field vector with respect to axes (x, y) of said sensor, upon rotation together of said vehicle and sensor, traces out and defines a locus curve (O) which has a center point (M), and in which the disturbance field causes a shift of the center point (M) of the locus curve from a null position in an orthogonal vectorial system, which shift is determined by the disturbance field present at the location of the magnetic field sensor, said method comprising, in accordance with the invention, the steps of determining field strength values (Hx max , Hy max ) which represent saturation of said sensor along each of its respective axes (x,y) and, iteratively, (a) securing the field sensor (11) at a new location in the vehicle; (b) moving the vehicle through 360°; (c) continuously measuring, during movement of the vehicle, field strength values and determining, in an evaluation circuit (10, 13) coupled to the field sensor (11), which of said measured values represent the maximum and minimum value, along each axis, of the entire field vector (Hg x , Hg y ) encountered during said 360° movement; and (d) determining the magnitude, along each axis, of the disturbance field (Hs x , Hs y ) at said new location; at least until the field strength of the disturbance field (Hs) is not greater than half the saturation field strength (Hx max , Hy max ) of the magnetic field sensor (11).