The development of new image-based techniques is allowing a radical change in theenvironmental monitoring field. The fundamental characteristics of these methods are related tothe possibility of obtaining non-intrusive measurements even in adverse circumstances, such ashigh flow conditions, which may seriously threaten the operators’ safety conditions in traditionalapproaches.Optical techniques, based on the acquisition, analysis and elaboration of sequences of imagesacquired by digital cameras, are aimed at a complete characterization of the river instantaneoussurface velocity field, through the analysis of a floating tracer, which may be naturally present orartificially introduced. The growing availability of a new generation of both low-cost optical sensorsand high-performing free software programs for image processing, is a key aspect explaining therapid development of such techniques in recent years. The best known optical techniques are thelarge scale particle velocimetry (LSPIV) and the large scale particle tracking velocimetry (LSPTV).This work is aimed to analyze and compare the performance of the two most common freesoftware packages based on LSPIV (i.e. the PIVlab and the FUDAA-LSPIV), which use different crosscorrelationalgorithms. The test is carried out by analyzing several sequences of both syntheticimages and real frames acquired on natural rivers under different environmental conditions (withtracers artificially introduced). An image sequences generator has been implemented ad-hoc withthe aim to create, under fixed configurations, synthetic sequences of images, simulating uniformlydistributed tracers moving under controlled conditions. The various configurations arecharacterized by different parameterization in terms of: (i) flow velocity (S=slow or F=fast flowconditions, according to a logarithmic transverse flow profile); (ii) tracer particles size (CON= disksof constant diameter; VAR=disks of variable size with given mean diameter); (iii) seeding densityper frame (density: low -LD, medium -MD, high -HD).The synthetic sequences are processed by the two software packages together with the realsequences, analyzing the errors in terms of mean value of the surface velocity field and velocityalong a transverse transect, with respect to a benchmark velocity (i.e. that imposed in the imagesequence generator for the synthetic sequences and that deriving from the use of traditionalsensors, i.e. ADCP, for the real sequences).
|Numero di pagine||1|
|Rivista||GEOPHYSICAL RESEARCH ABSTRACTS|
|Stato di pubblicazione||Published - 2020|