Generally we think of geodesy as a science in which absolute measurements are made primarily for the purpose of determining the size and shape of the Earth. An engineering application is made through the extension of geodetic networks of horizontal and vertical control for the development and conservation of our natural resources through federal programs of mapping, reclamation, reforestation, water power, highway construction, and many other activities associated with the growth of our country. In all of ihese varied programs the scientist or engineer asks for coordinates or elevations of points which may be used as references in the further development of his own work. It is fundamental to him that these reference points remain fixed.