1. A system for drawing a stream and road centerline based on a Geographic Information System (GIS), the system comprising: a system main module configured to drive the system for drawing the stream and road centerline necessary for accurate GIS-based linear map production; a spatial database in which a graphic database for storing a plurality of pieces of graphic data, in which positional information of points of a stream and road contour line is stored in the form of a digital map, is established; a centerline vertex position automatic detecting and storing module included in the system main module and configured to perform a preprocessing process of retrieving data of a region where centerline drawing is necessary, to automatically detect the positions of points, through which the centerline passes, and potential vertexes which will be included in the centerline in the future, and to extract and store the positional information of the points in the form of a digital map; a centerline drawing, editing and storing module included in the system main module and configured to draw and edit the centerline using the positional information of the vertexes processed by the centerline vertex position automatic detecting and storing module and to store the centerline as a linear map; and a display unit configured to display the result of drawing the centerline using the system on a screen, wherein the centerline vertex position automatic detecting and storing module performs the preprocessing procedure of retrieving a stream or road map stored in the spatial database and transforming the stream or road map into data available in the module, includes an algorithm for detecting a maximum inscribed circle of the points which are the positions of the potential vertexes of the centerline, and a center point of the maximum inscribed circle, transforms the extracted positional information of the potential vertexes into a digital map, and stores the digital map, wherein the centerline vertex position automatic detecting and storing module extracts all vertexes present on a contour line of the stream and road based on the GIS in order to accurately detect the positions of the potential vertexes of the centerline, generates a line bisecting an interior angle at a certain vertex point of the target section based on the vertexes of the contour line, defines a point intersecting an opposite contour line, sets a point bisecting the distance between the two vertexes to an initial center point of a maximum inscribed circle, sets the length of a segment connecting two vertexes to the diameter of an initial circle for calculating the maximum inscribed circle having the center point on the line bisecting the interior angle of a certain vertex, calculates a Minimum Enclosing Rectangle (MER) of the circle having the initial center point and the diameter of the initial circle, repeats the calculation with respect to all the vertexes of the target section, calculates an MER of a segment connecting each vertex and a subsequent vertex, and calculates a shortest distance between the segment connecting each vertex and the subsequent vertex and the initial center point if the two MERs overlap, wherein, as the calculated shortest distance less than the radius of the initial circle indicates that the contour line of the circle passes through the outside of the contour line of the target section, the centerline vertex position automatic detecting and storing module stores a set of the calculated shortest distance, two vertexes forming the segment which is currently being used to calculate the shortest distance and a vertex having a shortest distance from the initial center point on the segment, which is currently being used to calculate the shortest distance, in an analysis target set as an analysis target for calculating the maximum inscribed circle, generates the maximum inscribed circle, which touches the inside of the stream and road, from the analysis target set generated by performing the process with respect to all stream contour lines, and regards the position of a center point of the maximum inscribed circle as the position of a potential vertex included in the centerline so as to store positional information of all the vertexes, and wherein the centerline drawing, editing and storing module retrieves the vertexes extracted and stored by the centerline vertex position automatic detecting and storing module, performs snapping configuration for detecting the accurate positions of the vertexes based on the GIS and configuration for generating a new linear graphic, confirms and selects the positions of the vertexes extracted in a GIS-based environment, linearly connects and edits the vertexes, and stores the final result of connecting the centerlines as a linear digital map file.