Error quantification of particle position estimation on colour images for Particle Tracking Velocimetry

Abstract

Particle Tracking Velocimetry relies on an accurate determination of particle image centroids in order to carry out reliable 3D photogrammetric reconstruction and trajectory linking. Centroid estimation on monochrome images is usually carried out with subpixel accuracy. When utilising differently coloured tracer particles to facilitate assignment procedures for PTV, colour cameras are required. They feature Bayer mosaic colour filters, which reduce the apparent pixel resolution of each colour channel. The present work is a first approach allowing to quantify centroid errors for different combinations of centroid estimators and demosaicing procedures using simulated colour particle images and varying parameter sets. The centroid of mass estimator turns out to be the most reliable method for most demosaicing techniques, with mean errors in subpixel range. A customised colour defiltering approach seems to be superior in certain defined ranges of wavelengths, but requires a colour classification of particles a priori.