Effect of angle increments and morphological complexity on the application of photogrammetry on the shells of Turbo crassus, Angaria delphinus, and Thais aculeata

CAREY LOUISE B. ARROYO, MICHELLE I. GERVERO, MARIA MILAGROSA A. NULLA, and ZENNIFER L. OBERIO
Philippine Science High School – Western Visayas Campus, Brgy.Bito-on, Jaro, Iloilo City 5000, Department of Science and Technology – Science Education Institute, Philippines

Abstract
Photogrammetry is the act of generating a three-dimensional model using photographs taken from various angles around an object. It can be applied in various fields such as designing in architecture and documentation in historical researches and calculating volume and irregularity in biological researches. This study aimed to determine the extent of agreement between photogrammetric measurements and the direct measurements. Specifically, effects of the morphological complexity of the specimens and the angle increments utilized in the acquisition of photographs were explored. To do so, three sea snail shells with varying morphological complexities were chosen as specimens. Photographs of the shells were taken with the following angle increments: 5°, 8°, and 12° and were run through Autodesk Recap Photo. Body length and width were measured directly and photogrammetrically. These were statistically analyzed using Bland-Altman Plots and Two One-sided Test (TOST) for Equivalence. It was found that the three-dimensional models produced are accurate representations of the objects. Furthermore, results showed that accuracy of the model increases as angle increment increases and that as complexity of the shell increases, so does the accuracy of body length measurements.

Keywords: angle increments, morphological complexity, photogrammetry