1. A method for positioning on a digital map, comprising steps of: (a) transferring an image signal to an I/O module by a camera device, comprising a remote-control camera having parameters of panning, tilting and zooming, to be transformed into image data; (b) storing said image data in an image data base module and transferring said image data to be displayed by a display unit; (c) setting a monitored position in said image data, and transferring image coordinates of said monitored position to a transformation module; (d) transforming said image coordinates of said monitored position into object coordinates through said transformation module; and (e) inputting said object coordinates into a digital map module and displaying said monitored position and a digital map on said display unit, wherein said transformation module in step (d) processes transformations between said image coordinates of said monitored position of said remote-control camera and said object coordinates of said digital map of said digital map module according to a transformation function between said image coordinates and said object coordinates, wherein said transformation function is obtained through steps of: (k) obtaining a parameter model of panning, tilting and zooming of said remote-control camera through a bundle adjustment; (l) obtaining a plurality of control points of said remote-control camera separately corresponding to a plurality of control points of said digital map to obtain orientation parameters of said remote-control camera and calibration parameters of panning, tilting and zooming of said remote-control camera through a bundle adjustment; (m) substituting said orientation parameters of said remote-control camera and said calibration parameters of panning, tilting and zooming of said remote-control camera obtained in step (l) into said parameter model obtained in step (k) to obtain said transformation function between said image coordinates of said monitored position of said remote-control camera and said object coordinates of said digital map of said digital map module.