Fusion of UAV and Terrestrial Photogrammetry with Laser Scanning for 3D Reconstruction of Historic Churches in Georgia

Thomas Luhmann,Maria Chizhova,Denys Gorkovchuk

doi:10.3390/drones4030053

Abstract

In September 2018, photogrammetric images and terrestrial laser scans were carried out as part of a measurement campaign for the three-dimensional recording of several historic churches in Tbilisi (Georgia). The aim was the complete spatial reconstruction with a spatial resolution and accuracy of approx. 1 cm under partly difficult external conditions, which required the use of different measurement techniques. The local measurement data were collected by two laser scanning campaigns (Leica BLK360 and Faro Focus 3D X330), several UAV flights and two terrestrial image sets. The photogrammetric point clouds were calculated with the image-based modelling programs AgiSoft and RealityCapture taking into account the control points from the laser scans. The mean residual errors from the registrations or photogrammetric evaluations are 4–16 mm, depending on the selected software, size and complexity of the monument and environmental conditions. The best completeness and quality of the resulting 3D model was achieved by using laser scan data and images simultaneously. The article presents recent results obtained with RealityCapture and gives a critical analysis of accuracy and modelling quality.

Highlights

Difficult external conditions required the combination of different measuring techniques
For the Agisoft workflow, the photogrammetric point cloud will be merged with laser scans afterwards, e.g., in CloudCompare (At the time of paper writing, a new version of Agisoft Metashape allows importing of TLS point clouds, but the option of TLS and photogrammetric data fusion are not yet apparent)
The terrestrial laser clouds with and terrestrial images.images. Both testBoth objects differ in size, accessibility terrestrial laserpoint point clouds with and terrestrial test objects differ in size, and complexity

Summary

Introduction

In September 2018 photogrammetric images and terrestrial laser scans were carried out as part of a measurement campaign for the three-dimensional recording of three historical churches in Georgia. Combination of UAV and terrestrial image acquisition with terrestrial laser scans Use of data for future semantic segmentation studies. In a one-week measuring campaign, three churches were recorded with different measuring systems: Terrestrial laser scanners Faro Focus 3D X330 and Leica BLK360. For the Agisoft workflow, the photogrammetric point cloud will be merged with laser scans afterwards, e.g., in CloudCompare (At the time of paper writing, a new version of Agisoft Metashape allows importing of TLS point clouds, but the option of TLS and photogrammetric data fusion are not yet apparent). In RC, photogrammetric images and laser scans are processed simultaneously, no extra data fusion step is required

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