In theory, LBL requires a minimum of three ranges and knowledge of depth to calculate a unique position. However in the real-world, it is likely that one or more ranges will be slightly in error and so with only three ranges, it is impossible to detect and identify an erroneous range. By adding more ranges, typically five or more, it becomes easier to detect outliers and compute a high integrity position. This is known as redundancy.

When we include the extra position change information obtained from an LBL system aided with an inertial sensor, such as our SPRINT or SPRINT-Nav, we can reduce the number of ranges required as we now have a better understanding of the actual movement of the target and can use this information to identify and reject erroneous ranges. The amount of assistance this gives in detecting bad ranges depends on the geometry of the ranges and the trajectory of the target. So how sparse to make an array therefore depends on your vehicle path, array design and the integrity required for the positioning. If you have any questions about array optimisation, please email [email protected] for help and assistance.