1 Topic by stegman.kelly

  • stegman.kelly
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Hi all,
So Im using the 'track path' to track a single object (purple dot).
I right click, start 'track path'. Then I advance the frames until the dot stops moving. Then I 'end path tracking'. 
Heres the issue:
1) When I export to spreadsheet I get x,y and time(with frame number).
2) When I simply look at the video again on Kinovea with the tracking line, and the displacement label showing, the displacement label shows a different displacement.

The only thing I can think of is that the exported data measures displacement points referenced from the initial frame (where the tracking started), and possibly, the displayed label measures displacement as an interframe displacement.

Heres an example:
looking at the displacement label at then end of the path (frame 27305): d=905.35 pix
looking at the displacement on the exported spread sheet(frame 27305) : d=881.4 pix

Whats going on?
Thanks!

2 Reply by joan

  • joan
  • joan
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In the spreadsheet it is the x,y coordinates of each point.
In recent versions, these coordinates are relative to the origin of the coordinate system, as set up from Image > Coordinate system (or set up from a perspective grid system if using 0.8.20).

When using the "Distance" measurement label from the path configuration dialog, the label shows the total distance covered by the path up to the current point.

So the two functions are not meant to display the same values. In a way the data exported in the spreadsheet is lower level. You could recompute the total distance from the coordinates if needed.
Similarly, speed is not exported in the spreadsheet, but could be recomputed from the x,y,t coordinates.

Hope that helps.