Patent ID: 9612332
Date: 2017-04-04
CPC Classifications: G01B,G01S

Claim:
1. A method of calibrating a trigonometric-based ranging system in air and water, the trigonometric-based ranging system comprising a structured signal-emitting device for emitting a structured signal and a sensor having a field of view for sensing signals emitted by the structured signal-emitting device, the structured signal-emitting device and the sensor having a geometric relationship measured in air, the method comprising: (a) in each of air and water, determining a sensor matrix for the sensor therein respectively; (b) measuring rotation and translation of a sensor optical axis of the sensor relative to an ideal sensor optical axis substantially defined by a sensor housing in which the sensor is mounted, by determining the rotation and translation of a sensor co-ordinate system of the sensor in each of air and water concurrently, to provide a rotation/translation matrix for the field of view in each of air and water respectively; (c) measuring rotation of a device optical axis of the device relative to an ideal device optical axis substantially defined by a device housing in which the device is mounted, by determining a relative change in an angle of the structured signal, between the structured signal in air and the structured signal in water respectively, to generate a device rotation matrix to be applied to the structured signal; (d) applying the rotation/translation matrix to the structured signal; (e) applying the device rotation matrix to the structured signal, to determine an apparent geometric relationship of the structured signal-emitting device and the sensor in water; (f) measuring rotation and translation of a new sensor optical axis of a new sensor relative to an ideal new sensor optical axis substantially defined by a new sensor housing in which the new sensor is mounted, by determining the rotation and translation of a new sensor co-ordinate system of the new sensor in each of air and water concurrently, to provide a new rotation/translation matrix for the new sensor in each of air and water respectively; (g) determining at least one difference between the rotation/translation matrix and the new rotation/translation matrix; and (h) rotating and translating the rotation/translation matrix by said at least one difference, to adjust the rotation/translation matrix for at least one discrepancy between non-idealities associated with the sensor and the sensor housing, and new non-idealities associated with the new sensor and the new sensor housing, to provide a new rotation/translation matrix for the new sensor's field of view in air and water respectively.