  We use the Slovak and Czech video meteor observations, as well as video
meteoroid orbits collected in the CAMS, SonotaCo, EDMOND and DMS catalogues,
for an analysis of the distribution of meteoroid orbits within the stream of
the Geminids and of the dispersion of their radiants. We concentrate on the
influence of the measurement errors on the precision of the orbits obtained
from the video networks that are based on various meteor-detection software
packages and various meteor orbital element softwares. The observed orbital
dispersions in the Geminid stream described by the median absolute deviation
range from 0.029 to 0.042 1/AU for the video catalogues. The distribution of
the semi-major axes of video meteors in all the databases, except for the
Ondrejov (Czech) data, seem to be systematically biased in comparison with the
photographic and radio meteors. The determined velocities of the video data are
underestimated, probably as a consequence of the methods used for the
positional and velocity measurements. The largest shift is observed in the
EDMOND and SonotaCo catalogues. Except for the measurement errors which
influence the analyses and their interpretations, we also point out the problem
of the uncertainties of the numerical integration procedures that influence the
simulations' results. Several experimental integrations of the Geminids parent
asteroid, which we performed from the present to the past and then back to the
year 2015, showed that a complete reproduction, including also the mean
anomaly, is only possible for a time span of about 2700 years.
