1. A method for detecting a fallen person, comprising: generating an initial range image corresponding to a field of view of a data acquisition system; identifying a reference plane disposed in the field of view of the data acquisition system; determining one or more regions in the initial range image indicative of one or more objects disposed above the reference plane in the field of view of the data acquisition system; regenerating a range image corresponding to the field of view of the data acquisition system after a determined time period; comparing the regenerated range image with the initial range image to determine if the regenerated range image comprises a new object disposed above the reference plane; and determining whether the new object disposed above the reference plane is the fallen person if a height of the new object is less than a determined height and at least one of a volume and a surface area of the new object is greater than a determined value.