  While structure refinement is routinely achieved for simple bulk materials,
the accurate structural determination still poses challenges for thin films due
on the one hand to the small amount of material deposited on the thicker
substrate and, on the other hand, to the intricate epitaxial relationships that
substantially complicate standard X-ray diffraction analysis. Using a combined
approach, we analyze the crystal structure of epitaxial LaVO$_3$ thin films
grown on (100)-oriented SrTiO$_3$. Transmission electron microscopy study
reveals that the thin films are epitaxially grown on SrTiO$_3$ and points to
the presence of 90$^{\circ}$ oriented domains. The mapping of the reciprocal
space obtained by high resolution X-ray diffraction permits refinement of the
lattice parameters. We finally deduce that strain accommodation imposes a
monoclinic structure onto the LaVO$_3$ film. The reciprocal space maps are
numerically processed and the extracted data computed to refine the atomic
positions, which are compared to those obtained using precession electron
diffraction tomography. We discuss the obtained results and our methodological
approach as a promising thin film structure determination for complex systems.
