1. A target tracking system comprising: a plurality of N-dimensional (N is 1 or 2) angle sensors configured to observe targets to N-dimensional angle observed values; angle tracking apparatuses provided in association with the plurality of N-dimensional angle sensors and configured to calculate N-dimensional tracks for the respective targets by angle tracking using the N-dimensional angle observed values for the respective targets obtained by the corresponding sensors; (N+1)-dimensional track processing means for receiving N-dimensional angle observed values for the respective targets observed by the corresponding plurality of N-dimensional angle sensors and N-dimensional tracks for the respective targets calculated from the corresponding N-dimensional angle observed values for the corresponding targets to calculate distance information from the input information, adding the distance information to the input information, and generating and maintaining (N+1)-dimensional tracks for the respective targets; predicted value calculation means for calculating N-dimensional predicted values from the respective maintained (N+1)-dimensional tracks for the corresponding targets; and correlation determination means for determining whether or not the N-dimensional predicted value for each of the targets obtained by the predicted value calculation means is correlated with the N-dimensional angle observed value for the target, wherein if the correlation determination means determines that the N-dimensional predicted value is not correlated with the N-dimensional angle observed value, the (N+1)-dimensional track processing means generates a new (N+1)-dimensional track for the target based on the N-dimensional track corresponding to the N-dimensional angle observed value determined not to correlate with the N-dimensional predicted value, if the correlation determination means determines that the N-dimensional predicted value is correlated with the N-dimensional angle observed value, the (N+1)-dimensional track processing means updates and maintains the (N+1)-dimensional track maintained in association with the N-dimensional predicted value using the N-dimensional angle observed value determined to correlate with the N-dimensional predicted value.