1. A method for labeling feature clusters in frames of image data for optical navigation, said method comprising: identifying current feature clusters in a current frame of image data; correlating said current feature clusters in said current frame of image data with previous feature clusters in a previous frame of image data based on distances between said current and previous feature clusters; and labeling each of said current feature clusters with an identifier associated with one of said previous feature clusters that has been correlated with that current feature cluster.