Assessment of Submillimeter Precision via Structure from Motion Technique in Close-Range Capture Environments

Abstract

Creating 3D models through the Structure from Motion technique is a recognized, efficient, cost-effective structural monitoring strategy. This technique is applied in several engineering fields, particularly for creating models of large structures from photographs taken a few tens of meters away. However, discussions about its usability and the procedures for conducting laboratory analysis, such as structural tests, are rarely addressed. This study investigates the potential of the SfM method to create submillimeter-quality models for structural tests, with short-distance captures. A series of experiments was carried out, with photographic captures at a 1-meter distance, using different quality settings: camera calibration model, Scale Bars dispersion, overlapping rates, and the use of vertical and oblique images. Employing a calibration model with images taken over a test board and a set of Scale Bars (SB) appropriately distributed over the test area, an overlap rate of 80 percent, and the integration of vertical and oblique images, RMSE values of approximately 0.1 mm were obtained. This result indicates the potential application of the technique for 3D modeling with submillimeter positional quality, as required for structural tests in laboratory environments.

Figures (15)

• Figure 1: Distribution of the SBs along the edges of the sectors within the region of interest, while CBs were positioned across the area of the analyzed object
• Figure 2: Processing conducted representing the point cloud (in the background) and the positioning of the cameras at the time of capture (blue squares), in this processing, all images (vertical and oblique) are displayed.
• Figure 3: a) The represented capture set used vertical and oblique images, with rotation of ± 15° in Yaw, followed by captures with ± 15° in Pitch; (b) Representation of possible rotation movements of the camera.
• Figure 4: Representation of the mean lengths and Standard Deviation of the measurements of each positional element, obtained through a series of 5 measurements.
• Figure 5: RMSE values obtained for 3D modeling with three different camera calibration models, using sets of images of the test piece with 80% overlap and employing the maximum number of SBs and CBs, showing a significant advantage for the product that utilized the pre-calibrated PSC model.