2018 Volume 24 Pages 19-24
Photogrammetry of shallow water bottoms by UAV and SfM-MVS technology is attracting attention for its low cost and efficiency. One of the problems of this technique is the underestimation of water depth due to the refraction of light at the water surface. The issue is usually addressed by multiplying the apparent depth of water by a constant called refraction correction factor. Conventionally, 1.34 (relative refractive index of air and water) is used as the factor, but it is geometrically too small. In this study, we investigated the optimum refraction correction factor through 20 simulations by using a popular MVS software and 7 field experiments. The optimum values obtained in the field experiments was highly variable, although our simulation indicated that a single value is generally applicable.
