one of the challenges in video surveillance system is the detection of unwanted intruders in secure zones . these zones may be in large facilities such as airports , train stations , port facilities or warehouses . because many of these locations are outdoors , the presence of shadows is detected on images . in order to effectively eliminate these shadows which will therefore result in a usable figure , these shadows must be eliminated . this is accomplished by forming a contour box around the image and then reducing the shadows based on preset parameters in the software .