Gating is a technique used for eliminating unlikely observation-to-track pairings. A gate is formed about the predicted measurement and all observations that sat-isfy the gating relationship (falling within the gate) are considered for track updates. The manner in which the observations are actually chosen to update the track de-pends on the method of data association. For example the nearest neighbour method, global nearest neighbour, probabilistic data association method or multiple hypothe-ses method. These association methods are discussed in Chapter 6.
The possible gating techniques are: