72 U. S. COAST AND GEODETIC SURVEY. 



bisecting this line. For the parallel great circle take 

 QT=^~', FTlocates ^ and FZ7 parallel to OQ locates TJ, 

 the center of the required great circle projection. 



CONFORMAL POLYCONIC PROJECTIONS. 



Since we are to have a conformal projection, it is best 

 to treat the case for a sphere and then to take into account 

 the ellipsoidal shape in the same way that we did in treat- 

 ing the stereographic projections. 



In the treatment of the rectangular polyconic projec- 

 tions, we found that 



sm Q\ 



If the projection is to be conformal, it must be rectangular, 

 and, in addition, the scale at any given point must be the 

 same along the meridian that it is along the parallel, or 



If —le 



A-xn — A-p. 



Hence 



(ds . dp\ p rOO . ^ 

 ( J- cos d — ^f- )=—^ — TTTTT sm d, 

 \d<p dip/ cos <^ r(X) ^ 



p sm d \d(p dip/ 



*See p. 15. 



or 



