Some warning && matrix R computation && residuals

[wendyhh]

1 When I run program, many times the following warnings appear:
[ WARN] [1381953346.986521136]: fuzzy tracking triggered: 0.783476 limit: 0.1
[ WARN] [1381953347.654354944]: Negative scale detected: -0.0697402. Correcting to 0.1

2 Also I didn't find the related paper which describes how to compute R matrices.

3 Compare viconpose_sensor.cpp in second tutorial with pose_sensor.cpp, I found some difference when construct residuals:
pose_sensor.cpp: r_old(6, 0) = -2 * (state_old.q_wv_.w() * state_old.q_wv_.z() + state_old.q_wv_.x() * state_old.q_wv_.y()) / (1 - 2 * (state_old.q_wv_.y() * state_old.q_wv_.y() + state_old.q_wv_.z() * state_old.q_wv_.z()));
viconpose_sensor.cpp: q_err = (state_old.q_wv_ * state_old.q_ * state_old.q_ci_).conjugate() * z_q_;
r_old(6, 0) = -2 * (q_err.w() * state_old.q_wv_.z() + state_old.q_wv_.x() * state_old.q_wv_.y()) / (1 - 2 * (state_old.q_wv_.y() * state_old.q_wv_.y() + state_old.q_wv_.z() * state_old.q_wv_.z()));

I am not sure which one is right because I don't know what's the meaning of last element in residuals vector( the first three is position && second three is attitude).

Thanks in advance.