Disjointed data

[Oli14]

Hello,

I have recently completed, and am currently writing up (with a mere 6 hours left until the deadline, of course) a Masters research dissertation using 6 OptiTrack V100 cameras to pick up 6 reflective marker dots, 3 on the lateral edge of the right foot, and 3 on the superior surface of the foot. the cameras were placed in a slightly curved row from the participants' 12 oclock to 5 oclock.

My problems are that the data for 2 of my 9 participants is severely disjointed and cannot be analysed (I don't want to fix this problem, I just need to explain it and am stumped!) as the markers coordinates flip from column of data to another numerous times per second. Why might this be, please? This happened for all 6 markers for all participants at one time or another, and regularly for the 2 mentioned.

My other problem is the lack of spatial resolution for the markers on the superior surface of the foot, which were slightly closer to each other, about 2 cm apart in a row of 3. the data files for these markers contained large and regular gaps, was disjointed as above, and often claimed that 2 markers were 1, centered between the 2 markers.

I would be immensely appreciative of any suggestions as to why this might be. Thanks in advance!

Oli

[Oli14]

i should clarify the superior surface markers - it was marker - 2cm - marker - 2cm - marker.

[Oli14]

oh and I exported the data to a .csv file so had x,y,z coordinates for each marker

[VincentG]

Were you using the Arena, or Tracking tools software?

Did you have the objects setup as a rigid body, within the application?

Generally, if the RB, is not setup in an asymetrical configuration, that is unique to each rigid body, the software is going to have a hard time keeping the object defined correctly within the application. i.e. if multiply RB objects are similiar in shape, and configuration, the onjects by invert, or switch between being labeled as RB1, and RB2