PROBLEM TO BE SOLVED: To provide a land formation plan design supporting system capable of efficiently obtaining the present surveying terrain data with high accuracy and preparing plan, bird's-eye view or the like reflecting the data within a short time. SOLUTION: The land formation plan design supporting system produces contour data (F32, F7 and F8) from three-dimensional coordinate data (F31) simply measured at a random spot by GPS device (F1), total station (F2) or the like within a short time and three-dimensional mesh data (F9), and since plan and bird's-eye view data are prepared on the basis of these data (F9), measured data is faithfully reflected on plan/sectioned drawing and bird's-eye view without committing any input error, and the present situation can be easily and surely confirmed. In this system, since a view simulation picture corresponding to the bird's-eye data is indicated, the present three-dimensional inspection can be further and surely confirmed. By making a comparison between new an old three-dimensional mesh data, the volume of soil can be calculated.
