36 



TJ. S. COAST AND GEODETIC SURVEY. 



parallels become, respectively, the distances of the centers 

 and the radii of the meridians. In the table p^ and pp 

 denote, respectively, the radii of the meridians and of the 

 parallels ; /3m and ap, the distances of the centers ; 5m and 

 5p, the distances of the intersections of the meridians with 

 the Equator and of the parallels with the central meridian. 

 The table, of course, apphes to the sphere and not to the 

 ellipsoid. The values are given in terms of the earth's 

 radius, or they are the values for a sphere of imit radius. 



TABLE FOR THE STEREOGRAPHIC MERIDIAN PROJECTION. 



[In units of the earth's radius.] 



STEREOGRAPHIC HORIZON PROJECTION. 



In a stereographic projection the center of the map may 

 lie at any point upon the earth's surface. We have just 

 treated the case in which the center lay upon the equator. 

 If the center is to be in latitude a, we start with the same 

 equation in terms of the arc distance from the center and 

 the azimuth reckoned from the great circle perpendicular 

 to the meridian through the center. 



a sin jp cos cu 

 " 1 + cos f 



a sin ]) sin co 



y= 



1 + cos 2? 



