[N,X1,Y1,Z1]=textread('first.txt','%d%f%f%f');%读取一期观测值
[N,X2,Y2,Z2]=textread('second.txt','%d%f%f%f');%读取二期观测值
for (i=1:N-2)
    for (j=i+1:N-1)
        for (k=j+1:N)
        end
    end
end
X11=[X1(i),Y1(i),Z1(i);X1(j),Y1(j),Z1(j);X1(k),Y1(k),Z1(k)];%一期观测值3阶阵
X21=[X2(i),Y2(i),Z2(i);X2(j),Y2(j),Z2(j);X2(k),Y2(k),Z2(k)];%二期观测值3阶阵