has been experimentally found to be effective to merge these overlapping isolated regions also some relatively small regions caused by environmental noise are eliminated in a region level post processing step followed by object and feature extraction stages in other embodiments morphological processes other than or additional to dilation and erosion are effected one output 115 of the post processing circuitry 114 provides the object segmenting mask that is used to segment desired objects from the current image the other output 117 is processed by the feedback circuitry 118 and passed back to the background modelling circuitry to update the background model the decision circuitry 110 operates on a pixel by pixel basis and classifies those pixels that are sufficiently different from the statistical model by more than the threshold as being representative of a target object and those that are not as being other objects due to camera noise and illumination variations a certain number of pixels are likely to be classified as a target object even if they do not belong to it a high value of the threshold allows maintaining a low number of false detections on the other hand objects presenting a low contrast with respect to the target risk to be eliminated if the threshold is excessively high accordingly in some embodiments a statistical model is used to modify the thresholds in threshold selection process stage turning to fig2 reflectivity processing circuitry 104 processes the input image data 103 also using sensor spectral response data 121 of the camera to calculate the weights of parkkinen basis functions.