Potential of smartphone-based photogrammetry for measuring particle size and shape in field surveys

Abstract

In geological field surveys, the importance of particle size and shape is paramount, as these characteristics are essential for accurately interpreting subsurface conditions and earth surface processes. Traditional techniques for identifying particle morphology, like 3D laser scanners, are often costly or require complex operation, limiting their use in engineering. To address these limitations, this study introduces an Image Background Suppression (IBS) method based on smartphone photogrammetry, detailing its application in image collection and 3D particle model reconstruction. The study compares its results to those of 3D laser scanners, analyzing how camera quality, particle shape, shooting angle, and rotation angle impact the precision of the IBS method's reconstructions. The findings indicate that particle shape is the most significant factor affecting the accuracy of the 3D model, and that standard smartphones can capture high-quality photos for particle measurement. Additionally, the research identifies the optimal shooting angle to be between 45° and 60°, with a rotation angle of 15°. By utilizing these image collection parameters, the particle model generated by the IBS method exhibits an error rate of less than 1% in size and less than 5% in shape. Field tests of the IBS method further confirm its practicality and feasibility, highlighting its simplicity, versatility, low cost, and effectiveness. It is anticipated that the IBS method will become a widely adopted technology for measuring the size and shape of coarse aggregates due to these advantages.