1. A system comprising: a tag capable of emitting ranging signals, placed at at least two area of interest (AOI) feature points which can characterize an area of interest in a space; a positioning device in said space, configured to obtain location parameters of said AOI feature points based on the ranging signals from the tag; and a server, configured to characterize said area of interest based on the location parameters of said AOI feature points, wherein the server determines location parameters of the positioning device based on the obtained location parameters of said AOI feature points, and wherein when said area of interest is of an irregular shape, said positioning device is further configured to obtain location parameters of at least three AOI feature points on a boundary of the area of interest by means of the tag, so as to constitute a feature point sequence; said server is further configured to fit said feature point sequence so as to characterize the area of interest.