3D interpolation in a velocity field in sewers

In order to propose a new sewer inspection method, a velocity/turbidity profiler (Ubertone, UB Flow) has been tested in a laboratory. A 50 m glass flume has been adapted with several lateral connections (with a arnge of diameter, angle, intrusions, cracks), supplied by a 1 m3 tank. Placed just below the free surface on a rotating (to scan the wet section) and translating (along the main axe of the flume) structure, velocity profiles have been recorded and accurately positioned along the reach (with data from three laser distance meters and a 3 Mpix camera): a 3D cloud of raw velocities is created. After raw data pretreatment (deduction of translation velocity, Nyquist jumps correction, low quality data removal i.e. with low SNR threshold and vector projection corrections), five step-interpolation (adapted from [1]) methods have been implemented and tested: i) data filtering, ii) transformation to flume coordinates velocities, iii) isotropic gridding, iv) anisotropic gridding and v) continuity correction. These methods aim to produce contour lines and the quantification of different streamlines in the reach.