Last decades wave correlation methods have been developed to analyse structural vibration field measurements. The high spatial resolution that can be obtained nowadays by scanning laser vibrometry offers very dense measurement grids allowing the characterization of vibrating structures over a very wide frequency range. The principle of wave correlation approaches is to calculate the correlation between the vibration field measured at a given frequency and a vibrational field computed by means of an analytical model, parametrized by variables such as a (potentially complex) wavenumber vector. The mapping of this correlation allows inferring the type and parameters of the waves contributing to the vibration field. The post processing of such results can provide interesting properties such as dispersion laws, that are fundamental to understand the dynamic behavior of the material(s) constituting the structure. Up to now, the processing is well established for 1D vibration fields (the velocity of the structure along one direction only, the transverse direction most of the time), using either plane or cylindrical analytical waves. The study reported in the present work concerns the application of wave correlation techniques to 3D velocity fields (i.e. the 3D velocity vector measured on a 2D grid). The measurement of the tangential components of the velocity of the structure gives access to waves associated to in-plane motion, involving membrane and shearing deformation. A specific processing is required to correctly interpret such data, in order to properly separate the different wave types and to extract their specific dispersion laws. An experimental illustration of the technique is given, relying on 3D velocity fields measurements of a flat multilayer panel consisting of a honeycomb core stacked between two aluminum plates. Results are presented over a wide frequency range up to 50kHz, and resulting dispersion laws are compared to an analytical homogenized model of the structure.