Comparative Analysis of Structure-From-Motion Software’s –An Example of Letychiv (Ukraine) Castle and Convent Buildings

Letychiv (pl. Latyczów) is a town located in central Ukraine in the Khmelnytskyi Oblast. It has a unique and complicated history. Second World War left it in ruin, destroying buildings, infrastructure and decimating its once large population. Perhaps the most prominent part of the town currently is the building Dominican convent with adjoin Letychiv Assumption Church. This object is surrounded by what is left of the previously impressive Letychiv Castle, founded by Jan Potocki in 1598. Past 30 years have been dedicated by this small Catholic parish towards rebuilding monastery-castle-church complex. Since this is an ongoing project, it was decided to perform a photographic inventory of the current state of the construction and to create a 3D digital model of the castle, facade of the church and monastery, and the altar. This task have proven to be difficult due to complicated structure of the object. Facades and inner parts of the church are almost white with limited number of distinctive elements, painted in pail gold. Elements other than white are almost identical to each other. It leads to various errors in the processing of Structure-from-motion. This article describes how various versions of SfM algorithm work thru mention difficulties, compares results in terms of accuracy, level of detail and overall look. It also describes how SfM can help to document various stages of restoration of important historical objects.