  The present paper is part of a broader programme, exploring the possibility
of involving the Microsoft Kinect$^{\rm TM}$ sensor in the analysis of human
motion. In this study, the output obtained from the two available versions of
this sensor is critically examined. We demonstrate that the two outputs differ
in regard to the variation of the physical quantities involved in the modelling
of the human motion. As the original sensor has been found unsuitable for
applications requiring high precision, the observed differences in the output
of the two sensors call for the validation of the upgraded sensor on the basis
of a marker-based system.
