  We focus on the problem of timing errors in navigation camera as a case study
in a broader problem of the effect of a timing error in cyber-physical systems.
These systems rely on the requirement that certain things happen at the same
time or certain things happen periodically at some period $T$. However, as
these systems get more complex, timing errors can occur between the components
thereby violating the assumption about events being simultaneous (or periodic).
  We consider the problem of a surgical navigation system where optical markers
detected in the 2D pictures taken by two cameras are used to localize the
markers in 3D space. A predefined array of such markers, known as a reference
element, is used to navigate the corresponding CAD model of a surgical
instrument on patient's images. The cameras rely on the assumption that the
pictures from both cameras are taken exactly at the same time. If a timing
error occurs then the instrument may have moved between the pictures. We find
that, depending upon the location of the instrument, this can lead to a
substantial error in the localization of the instrument. Specifically, we find
that if the actual movement is $\delta$ then the observed movement may be as
high as $5\delta$ in the operating range of the camera. Furthermore, we also
identify potential issues that could affect the error in case there are changes
to the camera system or to the operating range.
