Stadimetric Curve

a set of points corresponding to equal values of some linear element. Stadimetric curves are a special case of lines of position where linear measurements are used.

Some examples of possible linear elements and the corresponding stadimetric curves in the plane are as follows: the distance from a given point (concentric circles), the difference between the distances from two points (hyperbolas), the sum of the distances from two points (ellipses), and the ratio of the distances from two points (eccentric circles).

On a sphere or ellipsoid, stadimetric curves are more complicated; for example, they may be small circles, geodesic circles, or geodesic hyperbolas.

By measuring two linear elements, it is possible to construct two stadimetric curves whose intersection yields a desired point. In navigation, stadimetric curves are used to determine rapidly the position of a ship or aircraft from a map on which a network of stadimetric curves has been drawn. In geodesy, stadimetric curves are used to determine the approximate coordinates of points.