National Geographic : 1914 Jun
MAP SHOWING THE NETWORK OE PRIMARY TRIANGULATION IN THE UNITED STATES, ABOUT 10,000 LINEAR MILES BY THE COAST AND GEODETIC SURVEY AND ABOUT 2,000 MILES BY THE LAKE SURVEY The Texas-California arc, indicated by shading in the lower left-hand portion of the illustration, and the one hundred and fourth meridian arc, similarly shown in the upper portion of the illustration, between the one hundredth and one hundred and tenth meridians, are the most recently completed of the larger arc. The former extends from central Texas to the Pacific coast, is 1,220 miles in length, covers an area of approximately 48,400 square miles, and determines the geographic positions of more than two hundred monumented stations and permanent objects. Connections were made with monuments of the international boundary between this country and Mexico and stations of detached triangulation by the United States Geological Survey. Primary triangulation is necessary as a framework for coordinating and placing on a single basis all maps and charts made by the Federal and State governments. Monuments of a number of State boundaries are already connected with the triangulation net, and should they and all other evidence of the boundaries be destroyed, it is possible to replace them within a very few feet. It is planned to extend this triangulation until no place in the country is more than one or two hundred miles from a station. Intermediate areas will be controlled by triangulation of a lower order. In addition to the primary, there are many thousands of miles of secondary and tertiary triangulation along the coasts and inland, which furnish the immediate control of charts and maps (see also pages 663-665).