MEASUREMENT OF CLADODES OF Opuntia spp. IN THREE-DIMENSIONAL PHOTOGRAPHS

Abstract

The species of the genus Opuntia (prickly pear) are edible cacti, native to America; its leaves, transformed into spines, make its handling difficult. In this research, we measured the area of Opuntia cladodes using 3D photographs in order to avoid the handling of the spinous plant. The proposed in situ method is “non-destructive”, it generates immediate results, it is low cost, employs cutting edge technology, and solves the problems that occur with the leaf area measuring methods cited in the references when applied to this spinous plant. Unlike 2D images, 3D images consider the inclination and curvature of the sample to determine its area. By applying multiple linear regression, we can calculate the inclination from a sample to the center of the image. The measurement of cladodes allows us to evaluate the yield of a crop, decide the time for harvest, or survey and characterize wildlife specimens. To evaluate this strategy, we determined the area of 12 cladodes with the proposed method and five other strategies for comparison. The algorithm showed a 95% accuracy, as the best destructive strategies, but without damaging the plant; it also showed the best performance in terms of the time required for a result. The database with the generated 3D images, as well as the source code, can be downloaded for free from http://www.serconmur. com/area-foliar-3d.html.