question: public static double mercY ( double lat ) { if ( lat > 89.5 ) { lat = 89.5 ; } if ( lat < - 89.5 ) { lat = - 89.5 ; } double temp = R_MINOR / R_MAJOR ; double es = 1.0 - ( temp * temp ) ; double eccent = Math . sqrt ( es ) ; double phi = Math . toRadians ( lat ) ; double sinphi = Math . sin ( phi ) ; double con = eccent * sinphi ; double com = 0.5 * eccent ; con = Math . pow ( ( ( 1.0 - con ) / ( 1.0 + con ) ) , com ) ; double ts = Math . tan ( 0.5 * ( ( Math . PI * 0.5 ) - phi ) ) / con ; double y = 0 - R_MAJOR * Math . log ( ts ) ; return y ; }
target:  Compute Y value of mercator projection.