Abstract
This paper discusses the issue of automation of orthoimage generation based on Terrestrial Laser Scanning (TLS) data and digital images. The following two problems are discussed: automatic generation of projection planes based on TLS data, and automatic orientation of digital images in relation to TLS data. The majority of popular software applications use manual definitions of projection planes. However, the authors propose an original software tool to address the first issue, which defines important planes based on a TLS point cloud utilizing different algorithms (RANdom SAmple Consensus–RANSAC, Hough transform, “region growing”). To address the second task, the authors present a series of algorithms for automated digital image orientation in relation to a point cloud. This is important in cases where scans and images are acquired from different places and at different times. The algorithms utilize Scale Invariant Feature Transform(SIFT) operators in order to find points that correspond in reflectance intensity between coloure images (Red Green Blue—RGB) and orthoimages, based on TLS data. The paper also presents a verification method using SIFT and Speeded-Up Robust Features (SURF) operators. The research results in an original tool and applied Computer Vision(CV) algorithms that improve the process of orthoimage generation.
Highlights
Developing geometric documentation is one of the most basic tasks in the fields of conservation policy and management of cultural heritage objects. 3D documentation is a prerequisite of conservation or restoration work on historical objects and sites
Such a1n696a8pproach, which is based on an assumed fixed scanning interval, explicitly defines the interpolation method that is applied for generation of the digital surface model (DSM) in the GRID form
Such an approach, which is based on an assumed fixed scanning interval, eRxempoliteciStelnys.d2e01fi5n, 7espatghee–pinagteerpolation method that is applied for generation of the digital surface model (DSM) in the GRID form
Summary
Developing geometric documentation is one of the most basic tasks in the fields of conservation policy and management of cultural heritage objects. 3D documentation is a prerequisite of conservation or restoration work on historical objects and sites. The TLS technique has a lot of limitations; for example,it is not possible to acquire sharp edges, poor quality or reflective surfaces, etc. Another issue is caused by areas with obstacles or hidden points. In many cases scanning data on cultural heritage objects exist already; it is only necessary to acquire high-resolution orthoimages with the use of additional, “free-hand” images. Development of metric documentation of complicated historical objects requires implementation of an automated technological process. Based on this experience the orthoimage generation process has been automated with the use of terrestrial laser-scanning data and “arbitrary” high-resolution images
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