**Navigation: Imperative to provide the robot-boat platform with sufficient situational awareness to facilitate intelligent movement!!**

**1. Triangulation ranging**

Triangulation is based on the premise of plane trigonometry: if we are given the the length of a side and two angles of a triangle it is possible to deduce the length of the other sides and remaining angle using Law of Sines

So triangulation ranging can give us length of B to target point P3 by measuring angles at P1 and P2. In the following figure we can see how this would work using an active ranging system (in this case a laser at P1 and detection sensor at P2). The laser at P1 emits energy which is reflected by the target at P3 – this is then received by the sensor at P2. Thus giving us the unknown angle and permitting us to determine the range from platform to P3 using Law of Sines (i.e. completing the triangle)

Limiting factors include:

- Reduced accuracy at increased range
- Missing parts/shadowing problem – this problem occurs when particular parts of the scene can only be observed by one viewing location (either P1 or P2; both not both)
- Possible errorĀ if an angle is close to 90 degrees

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