High resolution transmission electron microscopy experiments were performed to investigate nanoplatelets induced by ion implantation into a germanium wafer. Atomistic models were used for image simulation in order to get quantitative information from the experimental images. The geometrical phase shift analysis technique was also employed to measure the strain field induced by such defects. We discuss the limits and artefacts imposed by each approach and show how these approaches can be combined to study the atomic structure of such defects and the strain field they induce.