On the Uncertainty of the Image Velocimetry Method Parameters

• Published in: Hydrology Vol. 7; no. 3; p. 65
• Main Authors: Rozos, Evangelos, Dimitriadis, Panayiotis, Mazi, Katerina, Lykoudis, Spyridon, Koussis, Antonis
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01-09-2020
• Subjects: Algorithms; Cameras; Computer simulation; Confidence intervals; Equipment costs; Flow velocity; Hydrology; image velocimetry; Interrogation; LSPIV; Methods; Monte Carlo; Monte Carlo simulation; Parameter uncertainty; Parameters; Probability distribution; Probability theory; Random numbers; Remote sensing; Statistical analysis; Statistical methods; Statistics; stream discharge; Subjectivity; Surface flow; Surface velocity; Uncertainty; Unmanned aerial vehicles; Velocimetry; Velocity
• ISSN: 2306-5338; 2306-5338
• DOI: 10.3390/hydrology7030065

Image velocimetry is a popular remote sensing method mainly because of the very modest cost of the necessary equipment. However, image velocimetry methods employ parameters that require high expertise to select appropriate values in order to obtain accurate surface flow velocity estimations. This introduces considerations regarding the subjectivity introduced in the definition of the parameter values and its impact on the estimated surface velocity. Alternatively, a statistical approach can be employed instead of directly selecting a value for each image velocimetry parameter. First, probability distribution should be defined for each model parameter, and then Monte Carlo simulations should be employed. In this paper, we demonstrate how this statistical approach can be used to simultaneously produce the confidence intervals of the estimated surface velocity, reduce the uncertainty of some parameters (more specifically, the size of the interrogation area), and reduce the subjectivity. Since image velocimetry algorithms are CPU-intensive, an alternative random number generator that allows obtaining the confidence intervals with a limited number of iterations is suggested. The case study indicated that if the statistical approach is applied diligently, one can achieve the previously mentioned threefold objective.