echo on%--------------------------------------------------% PltNetEl%   Plots network error ellipses at each point.%   Note: Use a square aspect ratio for plot;%   i.e., use axis('square') command.%   M-files: plterrel.m% 7 Jul 96%--------------------------------------------------clearclear plterrel%----- Define 2d network coordinatesn=10;rand('normal');rand('seed',123456);x=rand(n,1)*100;  % northy=rand(n,1)*100;  % east%----- Define network covariance matrixr1=0.02;r2=0.01;az=45*pi/180;R=[cos(az) -sin(az); sin(az) cos(az)];Ci=R*diag([r1^2,r2^2])*R';C=zeros(n*2,n*2);for i=1:n  ind=(i-1)*2+(1:2);  C(ind,ind)=Ci;ends=1000;  % Scale factor for error ellipses%----- Plot network points & ellipses (plterrel)clg;axis('square');plot(y,x,'o');hold on;t=clock;for i=1:n  ind=(i-1)*2+(1:2);  plterrel(x(i),y(i),C(ind,ind),s);  hold on;endetime(clock,t)  % elapsed timegrid;title(['Network Error Ellipses (',num2str(s),'x scale)']);xlabel('East');ylabel('North');hold off;axis('normal');