Fixed mistake in 'docs/calibration_guide.doc'.
Fixed mistake in 'docs/calibration_guide.doc'.

team-diana/swissranger_camera,team-diana/swissranger_camera,OpenPTrack/open_ptrack,OpenPTrack/open_ptrack,chanbrown007/open_ptrack,OpenPTrack/open_ptrack,chanbrown007/open_ptrack,chanbrown007/open_ptrack