Abstract
Smartphones recently expanded the potential for low-cost close-range photogrammetry for 3D modeling. They enable the simultaneous collection of large amounts of data for a variety of requirements. It is possible to calculate image orientation elements and triangular coordinates in phases as in Relative and Absolute image orientation. This study demonstrates the photogrammetric 3D reconstruction approach that performs on tablets and smartphones as well. Images are taken with smartphone cameras of iPhone 6 and then calibrated automatically using normal calibration model for photogrammetry and computer vision on a PC, depend on Agisoft Lens add-on that imbedded in Agisoft program, and MATLAB camera calibration Toolbox, and by using an oriented bunch of images of chessboard pattern for large point cloud-based picture using matching. The camera calibration results indicate that the calibration processing routines pass without any error, and the accuracy of estimated IOPs was convenient compared with non-metric digital cameras and are more accurate in Agisoft Lens in terms of standard error. For the 3D model, 435 cameras were used, 428 cameras located from 435 are aligned in two photogrammetric software, Agisoft PhotoScan, and LPS. The number of tie points that are used in LPS is 10 tie points, and 4 control points which used to estimate the EOPs, and the number of tie points that are regenerated in Agisoft PhotoScan were 135.605 points, the number of Dense cloud 3,716,912 points are generated, for 3D model a number of 316,253 faces are generated, after processing the tiled model generated (6 levels, 1.25 cm/pix), the generated DEM having (2136×1774/pix), the dimensions of the generated high-resolution orthomosaic are (5520×4494, 4.47 cm/pix). For accuracy assessment, the Xerr. = 0.292 m, Yerr. = 0.38577 m, Zerr.= 0.2889 m, and the total RMS = 0.563 m in the estimated locations of the exterior orientation parameters.
Highlights
Image orientation has great importance because it precedes the process of reproducing threedimensional coordinates from two-dimensional images such as DTM, DSM, Orthophotos, and access to GIS [1]
Camera calibration is a key point in the accuracy of photogrammetry
The accuracy of every photogrammetric project is based on the accuracy of internal orientation parameters (IOP) and External orientation parameters (EOP)
Summary
Image orientation has great importance because it precedes the process of reproducing threedimensional coordinates from two-dimensional images such as DTM, DSM, Orthophotos, and access to GIS [1]. Orientation is a process in which the location and behavior of a camera, a photo, a model, or any such unit is determined in space, based on reference coordinates [2]. Internal orientation parameters (IOP) receive the incoming light cone into the camera lens to form the original display. The internal orientation parameters are focal length, principal point, and distortion elements [3]. External orientation parameters (EOP) are three-dimensional coordinates and three orientation angles. The orientation is the reconfigure relative perspective mode between a pair of images, while the absolute orientation comes after the relative orientation where the relationship between the model and the coordinate system is ground [4]. The main image modeling (using a digital camera) requires a mathematical formula to convert the two-dimensional image into a three-dimensional image [5]
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