function [fi,la,h] = hirvonen(x,y,z,a,e2)
i=1;    
p=sqrt(x^2+y^2);
B1 =atan(z/(p*(1-e2)));
etykieta = 0;

while etykieta < 1
    if i ~= 1
        B1 = B2;
    end;
        
    N = a/(sqrt(1-e2*sin(B1)^2));
    H = (p/cos(B1))-N;
    B2 = atan((z/p)*(1-(e2*(N/(N+H))))^(-1));
    if abs(B2-B1)<(0.000005/206265) etykieta = 1;  end;
    i = i+1;
end;

N = a/(sqrt(1 - e2 * sin(B2) ^ 2));
fi = B2;
h = p/cos(B2) - N;
la = atan(y/x);

if la <0
    la = la + pi;
end;

h = roundn(h, -3);