effect for this device, howeve,r some interesting symmetric
error exists on the two spheres.
Spehre #1 rectus - tiem. Bghero 32 sexduals - tc
TURNS
i
(a) (b)
Figure 10. Fitting residuals of the spheres.
The residuals (Figure 11) show comparable results to the plane
fitting test. It is nearly linear and about 0.1 to 0.5% of the
measurement distance. Based on this test, we may conclude that
Kinect has really good accuracy in from 0.7 to 2 m, and over
that range the standard deviations are noisier and seem to be
stochastic. The fitted point number per sphere is in range 45K
to 1.4K
Mean of residuals
Éphenedt i
9 Sebere 2 i
SEE Seti]
Figure 11. Fitting residuals.
In the case of feature detection and adjustment, the relative
accuracy has a large impact (Calignano et al., 2010). The
location variation of sphere centers describes this feature
detection accuracy reasonably well. Figure 12 shows that the
points’ standard deviation in the repeatability test is mostly
under 1 cm.
STO of center points
ss
STE Fam]
Figure 12. STD of center point location variation.
4. HUMAN MORPHOLOGIC MEASUREMENTS
Typical measurement range of human morphologic is exactly
the same as that of the Kinect. In addition, mostly only certain
parts of the human body are examined, i.e., the face. This
means the range up to 2 m is acceptable. Facial reconstruction
is a fast-growing business and requires accurate human
morphologic measurements. In addition, it is very essential to
have a prior face model in case of plastic surgery, for example,
after an accident. For this purpose, the Kinect gives a very good
solution since it’s widely available and inexpensive. The
opportunity of high speed data acquisition (30fps) is also a
benefit of this device, as it helps avoid errors on fast changing
(mimics) and moving human body. The accuracy is the only
limitation of this device, though it can be increased by camera
calibration (including special scaling factor) and using of
multiple devices. The post processing and model generation
should be done in a special way (Figure 13); some points can be
dropped and key points should be used with higher weight
(Varga et al., 2008).
Figure 13. Key points (red) locations on a human face (Varga
et al., 2008).
5. CONCLUSION
In our experiences, the Kinect sensor has shown good and
consistent performance. The tests confirmed that rather good
quality 3D imagery can be acquired in close range by this
absolutely inexpensive sensor. The availability of several open
source tools and the existence of an active user community
make the integration of the Kinect sensor fairly simple,
including basic data processing tasks too. While the Kinect is
not a typical mapping sensor, its performance level makes it
feasible to several applications, like human morphologic
measurements.
6. ACKNOWLEDGEMENTS
The research work is funded by Hungarian Scientific Research
Fund (OTKA no. 73251)
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