Abstract
Medium-cost devices equipped with sensors are being developed to get 3D measurements. Some allow for generating geometric models and point clouds. Nevertheless, the accuracy of these measurements should be evaluated, taking into account the requirements of the Building Information Model (BIM). This paper analyzes the uncertainty in outdoor/indoor three-dimensional coordinate measures and point clouds (using Spherical Accuracy Standard (SAS) methods) for Eyes Map, a medium-cost tablet manufactured by e-Capture Research & Development Company, Mérida, Spain. To achieve it, in outdoor tests, by means of this device, the coordinates of targets were measured from 1 to 6 m and cloud points were obtained. Subsequently, these were compared to the coordinates of the same targets measured by a Total Station. The Euclidean average distance error was 0.005–0.027 m for measurements by Photogrammetry and 0.013–0.021 m for the point clouds. All of them satisfy the tolerance for point cloud acquisition (0.051 m) according to the BIM Guide for 3D Imaging (General Services Administration); similar results are obtained in the indoor tests, with values of 0.022 m. In this paper, we establish the optimal distances for the observations in both, Photogrammetry and 3D Photomodeling modes (outdoor) and point out some working conditions to avoid in indoor environments. Finally, the authors discuss some recommendations for improving the performance and working methods of the device.
Highlights
The three-dimensional modeling of an object begins with the required data acquisition process for the reconstruction of its geometry and ends with the formation of a virtual 3D model that can be viewed interactively on a computer [1]
The precision indicated by the photogrammetry techniques, which reconstruct a scene in real time
The Root Mean Square Error (RMSE) is calculated to assess the quality of the points captured by EM and measured by means of photogrammetry and 3D Photomodeling
Summary
The three-dimensional modeling of an object begins with the required data acquisition process for the reconstruction of its geometry and ends with the formation of a virtual 3D model that can be viewed interactively on a computer [1]. There are passive measurement techniques, with modeling based on images (image-based modeling), which use optical or optical-electronic capture systems for extracting geometric information in the construction of 3D models [19] The former uses different types of laser scanners, while the latter employs photogrammetric or simple conventional cameras. Many studies have carried out such analysis for active measurement techniques [21,22,23] as in the case of passive measurement techniques [4,24,25] These are deduced in the first case for objects of medium format, with the use of handheld laser scanners, where an accuracy up to 0.1 mm can be achieved [26]; in the second case, using techniques of automated digital photogrammetry, precision is of the order of about 5 mm [27], but with the advantage of a smaller economic cost. To investigate the feasibility of coordinates, measurements and point cloud acquisition from a BIM perspective, further evaluation was performed in reference to the guidelines of the GSA for BIM Guide for 3D Imaging [32]
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