Calibration method for trigonometric-based ranging systems in multiple media

A method of calibrating a trigonometric-based ranging system comprising a structured signal-emitting assembly comprising a device for emitting at least one structured signal mounted in a device housing, the device housing substantially defining an ideal device axis, the trigonometric-based ranging system also comprising a sensor assembly comprising a sensor having at least one field of view in which said at least one structured signal is detectable by the sensor, the sensor being mounted in a sensor housing, the sensor housing substantially defining an ideal sensor axis, the structured signal-emitting device and the sensor having a geometric relationship measured in a first medium, the method comprising:

• (a) transmitting said at least one structured signal from the device via the first medium toward at least one point on a target object;
• (b) determining a first sensor matrix associated with the first medium upon the sensor sensing said at least one structured signal at said at least one point through the first medium;
• (c) transmitting said at least one structured signal from the device via a second medium toward at least one location on the target object;
• (d) determining a second camera matrix associated with the second medium upon the sensor sensing said at least one structured signal at said at least one location through the second medium;
• (e) measuring rotation and translation of a sensor axis of the sensor relative to the ideal sensor axis by measuring the rotation and translation of a sensor co-ordinate system thereof in each of the first medium and the second medium, to provide a rotation/translation matrix for said at least one field of view to adjust for non-idealities in the sensor assembly;
• and
• (f) measuring rotation of a device axis of the device relative to the ideal device axis by measuring a relative change in an angle between a plane defined by said at least one structured signal, between said at least one structured signal in the first medium and said at least one structured signal in the second medium respectively, to generate a device rotation matrix to be applied to said at least one structured signal to adjust for non-idealities in the structured signal-emitting assembly.