1. An interactive input system comprising: an input surface having at least two input areas; a plurality of imaging devices having at least partially overlapping fields of view encompassing at least one input regions within the input area; and a processing structure configured to process image data acquired by the imaging devices to track the position of at least two pointers within the input regions by: identifying consistent candidates in the processed image data to facilitate resolving ambiguities between the pointers, each of the consistent candidates comprising observations located in image frames captured by all of the plurality of imaging devices having a field of view encompassing a target's input region; determining the position of the consistent candidates by assigning a weight to the observations based on the clarity of the observations; wherein the observations are clear when the imaging devices have a clear view of the observations and the consistent candidates are merged when the imaging devices have a merged view of a plurality of the observations, and wherein a first weight is assigned to the clear observations, the first weight having predefined value, and a second weight is assigned to the merged observations, the second weight being less than the first weight.