;
;  fsnspp: north stereographic polar projection
;
FUNCTION fsxspp, plam, pphi
;
rpi = double( 2.*asin( 1. ))
rad = double( rpi/180.)
;
z = double( 2. * cos( rad*plam ) * tan( rpi/4. - rad*pphi/2. ))
;
return, z
END