“…The loosely-coupled approach treats the inertial and vision units as two separate filters running at different rates and exchanging information, while the tightlycoupled approach combines them into a single, statistical filter. Among the loosely-coupled approaches are the works of [8], [9], [10], [11], [12], [13], [14], [15], [16], while among the tightly-coupled ones are those of [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27].…”