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

Abstract

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.

Multi-Variant TLS and SfM Photogrammetric Measurements Affected by Different Factors for Determining the Surface Shape of a Thin-Walled Dome

“…An important parameter is the required number of photos on which the same points are found. Photoscan relies on points found on a minimum pair of photos, whereas ContextCapture needs to find a point on at least three photos in order to be effectively used [ 26 ]. Thanks to the use of points with known coordinates which are identified on images, it is also possible to give the model a proper geo-reference and scale.…”

Unmanned Aerial Vehicles (UAVs) for Physical Progress Monitoring of Construction

“…The result of this algorithm is a low-quality, sparse point cloud, which is densified and enhanced by MVS [ 43 ], significantly increasing the number of points in the cloud, generating a deliverable with metric and visual information of the recorded surface [ 36 ]. A variety of software exists on the market today capable of applying the aforementioned algorithms sequentially and automatically with user-friendly interfaces [ 44 ].…”

The Impact of Photo Overlap, the Number of Control Points and the Method of Camera Calibration on the Accuracy of 3D Model Reconstruction

“…Photogrammetric 3D modeling based on the SfM algorithm may be, among others, used for the purpose of architectural visualization [3], archaeology [4,5], environmental and climate monitoring [6,7], geomorphology [8], medicine [9,10]. The SfM method is also the leading one in cultural heritage recording [11] because of several factors: contactless method of data acquisition, no need to carry bulky tools to remote and hard to reach regions, high degree of accuracy and the relatively low costs of this method [12][13][14]. Nowadays, photogrammetric methods based on SfM are also commonly used in augmented and virtual reality, something which becoming a pressing issue in cultural heritage studies [15] and its alternative representations on the Web [16].…”

“…A sparse point cloud and information about camera positions and calibration are the results of the first stage of the SfM algorithm implementation, afterwards a dense point cloud can be generated [22]. Furthermore, different approaches towards the implementation of the SfM algorithm may be found in various photogrammetric software [12,19]. The scope of this manuscript does not allow to fully explore the topic of the SfM algorithm.…”