function ifix=findfixed(C3)% FINDFIXED  Finds index of fixed station or most tightly%   constrained station based on smallest variances in a%   3D covariance matrix. Stations with the small sum of%   coordinate variances is selected as fixed station.% Version: 8 Apr 03% Useage:  ifix=findfixed(C3)% Input:   C3   - 3D covariance matrix% Output:  ifix - index (sequence number) of fixed station% Externals: nrows (Utils toolbox)if (nargin~=1)  error('Incorrect number of input arguments');endn=nrows(C3)/3;vsum=sum(reshape(diag(C3),3,n));ifix=find(vsum==min(vsum));