Iteratively loop for computing (WHILE)

I have this function and I have to make it compute my data iteratively. The new values obtained at final (Xa, Ya, Za, Ta) must be used as new values for iteration until (X(1)(dx),X(2)(dy), X(3)(dz)) < eps..I have trouble in putting the "while" command in the right place. I know this is very simple, and I may be a moron for not being able to figure this myself..but at this point I can't find the right solution..I would appreciate if anyone would help me with a hint.

function [P,DP] = compute_position(poz_apr,CoordSV,PR)

%Speed of light m/s
c = 0.299792458e9;

%Aproximate position
Xo=poz_apr(1);
Yo=poz_apr(2);
Zo=poz_apr(3);
To=poz_apr(4);

%Satellite coordinates
SVx=CoordSV(1,:)';
SVy=CoordSV(2,:)';
SVz=CoordSV(3,:)';
SVt=CoordSV(4,:)';

%Corrected pseudodistance
PR=PR+(SVt.*c);

%Geometric distance
p=sqrt((SVx-Xo).^2+(SVy-Yo).^2+(SVz-Zo).^2);

% Free terms vector
L=PR-p;

%Partial derivatives
DX= -(SVx-Xo)./p;
DY= -(SVy-Yo)./p;
DZ= -(SVz-Zo)./p;
DT = ones(length(PR),1).*(-c*1e-9);

%Coeff matrix
A=[DX DY DZ DT];

%Unknown terms (dx dy dz dt) matrix
X = inv(A'*A) * A' * L;

%Corrected position
Xa=Xo + X(1); % dx= X(1)
Ya=Yo + X(2); % dy= X(2)
Za=Zo + X(3); % dz= X(3)
Ta=To + X(4); % dt= X(4)

P=[Xa Ya Za Ta];
DP=[X(1); X(2); X(3); X(4)];

Answer 1

[Geoff Hayes]

Since Xo, Yo, Zo, and To represent the approximate position and the code refines/corrects the position to Xa, Ya, Za, and Ta then it seems that you should put the while loop in the code where you first use Xo, Yo, Zo, and To i.e. at the calculation of the geometric distance ,replacing the o variables with the a ones.

[Sebastian Ciuban]

Thank you for your advise!