Manual Feature Engineering with 3D Motion Capture Data

Second Experiment: Calibration Testing

Task Description

At least two steps on each side are recorded using the Xsens MVN system for motion data and a digital camera for a visual analysis of single steps. The goal was to test the calibration of the Xsens MVN system.

Materials and Methods

The setup was quite similar to the first experiment, but only one bar was used.

Results

The data from the following tables could be found in the file experiment2-walking.ods.

Declarations

Step Number
starting point, both feed side by side.
Side
left or right foot earlier
Time
time of reading
Time [s]
relative time of reading
Position Straw (Front)
Position of straw (front of straw) on the measuring leash
Position relative
The measuring leash was fixed on the floor with ascending numbers in the walking direction.
Step Length (right/left)
See step length definition considering both left and right foot
Step Length (side)
See side specific step length definition
Accuracy on Photo
Quality of image regarding the accuracy of the measurement point.

The step lengths of all walks have been read from image files taken by a second person.

Walk12

Video of Walk12 showing a person taking walking several steps along a bar.

Visualised Movement Data

Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Positions of RightFoot and LeftFoot in comparison with all other positions.
Positions of RightFoot and LeftFoot in comparison with all other positions.
Euclidian distance between the segments RightFoot and LeftFoot.
Euclidian distance between the segments RightFoot and LeftFoot.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Absolute velocity values of the segments RightFoot and LeftFoot.
Absolute velocity values of the segments RightFoot and LeftFoot.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Absolute acceleration values of the segments RightFoot and LeftFoot.
Absolute acceleration values of the segments RightFoot and LeftFoot.
Comparison between the absolute velocity values and the euclidian distances of the segments RightFoot and LeftFoot.
Comparison between the absolute velocity values and the euclidian distances of the segments RightFoot and LeftFoot.

Original call: ./calcStepLength --inputfile="../experiments/experiment2/walk12.mvnx" --outputdir="online/images/diagrams/walk12/" --segments="LeftFoot, RightFoot" --format="png" --title="walk12" --colors="blue, red, green, cyan, orange, darkblue, darkred" --min="500" --max="10000"

Measured Step Lengths

Step Number Side Time[s] Time Position Straw (Front) Position relative Step Length (right/left) Step Length (side) Accuracy on Photo
0 left 00:00:00 15:30:47 -3.8 0 good
0 right 00:00:00 15:30:47 -1.1 2.7 2.7 good
1 left 00:00:02 15:30:49 54.8 58.6 55.9 58.6 good
2 right 00:00:05 15:30:52 108.5 112.3 53.7 109.6 bad
3 left 00:00:07 15:30:54 158 161.8 49.5 103.2 good
4 right 00:00:10 15:30:57 199 202.8 41 90.5 good
Experimental data for Walk12.

Computed Step Lengths

Step Number Segment Begin[ms] End[ms] Step Length (side)
0 RightFoot 1175 1407 0
1 LeftFoot 4756 5052 0
2 RightFoot 6886 7363 107.48
3 LeftFoot 9247 9702 97.92
Computed data for Walk12.
The calculated step lengths of LeftFoot.
The calculated step lengths of LeftFoot.
The calculated step lengths of RightFoot.
The calculated step lengths of RightFoot.
Comparison of absolute velocity and distance between RightFoot and LeftFoot.
Comparison of absolute velocity and distance between RightFoot and LeftFoot.
Comparison of absolute velocity and Z position between RightFoot.
Comparison of absolute velocity and Z position between RightFoot.
Comparison of absolute velocity and Z position between LeftFoot.
Comparison of absolute velocity and Z position between LeftFoot.
3D positions of RightFoot and LeftFoot together with calculated points of steps.
3D positions of RightFoot and LeftFoot together with calculated points of steps.
Calculated step lengths for LeftFoot and RightFoot.
Calculated step lengths for LeftFoot and RightFoot.

Original call: ./calcStepLength --inputfile="../experiments/experiment2/walk12.mvnx" --outputdir="online/images/diagrams/walk12/" --format="png" --title="walk12" --colors="blue, red, green, cyan, orange, darkblue, darkred" --min="500" --max="10000"

Comparison of Measured and Computed Step Lengths

Step Number Exp Step Number Comp Side Step Length Exp[cm] Step Length Comp[cm] Difference[cm] Accuracy on Photo
2 2 right 109.6 107.48 2.12 bad
3 3 left 103.2 97.92 5.28 good
Compared steplengths from Walk12.
Comparison of measured and computed step lengths as csv table.
Comparison of measured and computed step lengths as csv table.
Comparison of measured and computed step lengths as barplot.
Comparison of measured and computed step lengths as barplot.
Comparison of measured and computed step lengths as scatterplot.
Comparison of measured and computed step lengths as scatterplot.

Original call: ./compareStepLength --inputcomp="online/images/diagrams/walk12/steplengths.csv" --inputexp="online/tables/experiment2/experiment2-walking-walk12.csv" --outputdir="online/images/diagrams/walk12/" --format="png" --title="walk12" --stepscomp="2-3" --stepsexp="2-3" --colors="blue, red, green, cyan, orange, darkblue, darkred"

Walk13

Video of Walk13 showing a person taking walking several steps along a bar.

Visualised Movement Data

Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Positions of RightFoot and LeftFoot in comparison with all other positions.
Positions of RightFoot and LeftFoot in comparison with all other positions.
Euclidian distance between the segments RightFoot and LeftFoot.
Euclidian distance between the segments RightFoot and LeftFoot.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Absolute velocity values of the segments RightFoot and LeftFoot.
Absolute velocity values of the segments RightFoot and LeftFoot.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Absolute acceleration values of the segments RightFoot and LeftFoot.
Absolute acceleration values of the segments RightFoot and LeftFoot.
Comparison between the absolute velocity values and the euclidian distances of the segments RightFoot and LeftFoot.
Comparison between the absolute velocity values and the euclidian distances of the segments RightFoot and LeftFoot.

Original call: ./calcStepLength --inputfile="../experiments/experiment2/walk13.mvnx" --outputdir="online/images/diagrams/walk13/" --segments="LeftFoot, RightFoot" --format="png" --title="walk13" --colors="blue, red, green, cyan, orange, darkblue, darkred" --min="500" --max="7800"

Measured Step Lengths

Step Number Side Time[s] Time Position Straw (Front) Position relative Step Length (right/left) Step Length (side) Accuracy on Photo
0 left 00:00:00 14:31:37 -3.8 0 good
0 right 00:00:00 14:31:37 -1.1 2.7 2.7 good
1 left 00:00:01 14:31:38 50.5 54.3 51.6 54.3 good
2 right 00:00:03 14:31:40 99.5 103.3 49 100.6 good
3 left 00:00:05 14:31:42 148.5 152.3 49 98 good
4 right 00:00:07 14:31:44 196.5 200.3 48 97 good
09:28:23
Experimental data for Walk13.

Computed Step Lengths

Step Number Segment Begin[ms] End[ms] Step Length (side)
0 RightFoot 1042 1257 0
1 LeftFoot 3222 3511 0
2 RightFoot 5018 5348 100.09
3 LeftFoot 7091 7404 95.39
Computed data for Walk13.
The calculated step lengths of LeftFoot.
The calculated step lengths of LeftFoot.
The calculated step lengths of RightFoot.
The calculated step lengths of RightFoot.
Comparison of absolute velocity and distance between RightFoot and LeftFoot.
Comparison of absolute velocity and distance between RightFoot and LeftFoot.
Comparison of absolute velocity and Z position between RightFoot.
Comparison of absolute velocity and Z position between RightFoot.
Comparison of absolute velocity and Z position between LeftFoot.
Comparison of absolute velocity and Z position between LeftFoot.
3D positions of RightFoot and LeftFoot together with calculated points of steps.
3D positions of RightFoot and LeftFoot together with calculated points of steps.
Calculated step lengths for LeftFoot and RightFoot.
Calculated step lengths for LeftFoot and RightFoot.

Original call: ./calcStepLength --inputfile="../experiments/experiment2/walk13.mvnx" --outputdir="online/images/diagrams/walk13/" --format="png" --title="walk13" --colors="blue, red, green, cyan, orange, darkblue, darkred" --min="500" --max="7800"

Comparison of Measured and Computed Step Lengths

Step Number Exp Step Number Comp Side Step Length Exp[cm] Step Length Comp[cm] Difference[cm] Accuracy on Photo
2 2 right 100.6 100.09 0.51 good
3 3 left 98 95.39 2.61 good
Compared steplengths from Walk13.
Comparison of measured and computed step lengths as csv table.
Comparison of measured and computed step lengths as csv table.
Comparison of measured and computed step lengths as barplot.
Comparison of measured and computed step lengths as barplot.
Comparison of measured and computed step lengths as scatterplot.
Comparison of measured and computed step lengths as scatterplot.

Original call: ./compareStepLength --inputcomp="online/images/diagrams/walk13/steplengths.csv" --inputexp="online/tables/experiment2/experiment2-walking-walk13.csv" --outputdir="online/images/diagrams/walk13/" --format="png" --title="walk13" --stepscomp="2-3" --stepsexp="2-3" --colors="blue, red, green, cyan, orange, darkblue, darkred"

Free Walk

Video of Walk14 showing a person walking without further disturbance.

Visualised Movement Data

Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Positions of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Positions of RightFoot and LeftFoot in comparison with all other positions.
Positions of RightFoot and LeftFoot in comparison with all other positions.
Euclidian distance between the segments RightFoot and LeftFoot.
Euclidian distance between the segments RightFoot and LeftFoot.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Velocities of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Absolute velocity values of the segments RightFoot and LeftFoot.
Absolute velocity values of the segments RightFoot and LeftFoot.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are the same.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Accelerations of RightFoot and LeftFoot in x, y and z direction. Note that the scales are different.
Absolute acceleration values of the segments RightFoot and LeftFoot.
Absolute acceleration values of the segments RightFoot and LeftFoot.
Comparison between the absolute velocity values and the euclidian distances of the segments RightFoot and LeftFoot.
Comparison between the absolute velocity values and the euclidian distances of the segments RightFoot and LeftFoot.

Original call: ./calcStepLength --inputfile="../experiments/experiment2/walk14.mvnx" --outputdir="online/images/diagrams/walk14/" --segments="LeftFoot, RightFoot" --format="png" --title="walk14" --colors="blue, red, green, cyan, orange, darkblue, darkred" --min="800" --max="4500"

Computed Step Lengths

Step Number Segment Begin[ms] End[ms] Step Length (side)
0 RightFoot 1158 1405 0
1 LeftFoot 1759 2236 0
2 RightFoot 2434 2871 115.2
3 LeftFoot 3119 3532 110.17
4 RightFoot 3928 4143 92.73
Computed data for first steps of Walk14.
The calculated step lengths of LeftFoot.
The calculated step lengths of LeftFoot.
The calculated step lengths of RightFoot.
The calculated step lengths of RightFoot.
Comparison of absolute velocity and distance between RightFoot and LeftFoot.
Comparison of absolute velocity and distance between RightFoot and LeftFoot.
Comparison of absolute velocity and Z position between RightFoot.
Comparison of absolute velocity and Z position between RightFoot.
Comparison of absolute velocity and Z position between LeftFoot.
Comparison of absolute velocity and Z position between LeftFoot.
3D positions of RightFoot and LeftFoot together with calculated points of steps.
3D positions of RightFoot and LeftFoot together with calculated points of steps.
Calculated step lengths for LeftFoot and RightFoot.
Calculated step lengths for LeftFoot and RightFoot.

Original call: ./calcStepLength --inputfile="../experiments/experiment2/walk14.mvnx" --outputdir="online/images/diagrams/walk14/" --format="png" --title="walk14" --colors="blue, red, green, cyan, orange, darkblue, darkred" --min="800" --max="4500" --distepsilon="0.5"

Discussion

As shown in Walk13 the calibration was quite accurate, but had some difficulties with the shoes of the person wearing the Xsens MVN system, which likely caused the problems in Walk12. As the feet of the person wearing the Xsens MVN system are quite smaller than the shoes, the contact detection on the ground was not working properly. Reprocessing the data of Walk12 with manual adjustments was found to be time consuming and insufficient.

Conclusion

To record data with high accuracy not only the calibration process, but also the clothes and shoes need to be considered. Accordingly to improve measurement using the Xsens MVN system it is recommended to wear tight fitting shoes. Also the KiC Engine Mode of the Xsens MVN system as described in the MVN User Manual in section 8.2 (page 32) and 18.4 (pages 85-86, MV0391P, Revision B, from May 26th 2010) might improve the quality of measurements on the lower limbs.