A position-finding system is comprised of a terminal having a global positioning system (GPS) for finding a position thereof, and a server which calculates altitude data, based on terrain data in an area in which the terminal is. The terminal includes a controller which selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured, in accordance with the altitude data provided from the server.