The point clouds obtained from Structure from Motion (SfM) photogrammetry need a scale factor correction if are used for quantitative evaluations as well as surface variations, volume estimates, and so on. The scale factor is required also for multitemporal models comparison. It can be achieved using homologous points, that is, points from artificial or natural elements detectable in the point clouds and just measured with independent and external measurements. In this work two different and independent approaches for the recognition, measurement and comparison of homologous points aimed at calculating the corresponding scale factors are shown. The first approach is based on the measurement of positions of artificial targets by means of realtime kinematic satellite navigation (RTK GNSS); the second one is based on the extraction of homologous points from TLSbased morphological maps. The results, influenced by the errors of the performed measurements, show a 0.04% discrepancy between the scale factors. Although this study concerns a specific case and therefore is not representative or exportable to general situations, it highlights the need to carefully evaluate the corrections applied to the scale factor in order to avoid errors of interpretation and, therefore, allow meaningful comparisons between multitemporal models aimed at extracting information on surface variations.