code: function phi1z(eccent, qs) {
          var sinphi, cosphi, con, com, dphi;
          var phi = asinz(0.5 * qs);
          if (eccent < EPSLN) {
              return phi;
          }
  
          var eccnts = eccent * eccent;
          for (var i = 1; i <= 25; i++) {
              sinphi = Math.sin(phi);
              cosphi = Math.cos(phi);
              con = eccent * sinphi;
              com = 1 - con * con;
              dphi = 0.5 * com * com / cosphi * (qs / (1 - eccnts) - sinphi / com + 0.5 / eccent * Math.log((1 - con) / (1 + con)));
              phi = phi + dphi;
              if (Math.abs(dphi) <= 1e-7) {
                  return phi;
              }
          }
          return null;
      }
docs: /* Function to compute phi1, the latitude for the inverse of the
  Albers Conical Equal-Area projection.
  -------------------------------------------