Flow mapping is what most fluid engineers are interested in. Especially, for comparison with results of flow visualisation or numerical computations, it has been a constant demand to provide information about the flow field in this form.
At the same time, the flow map is considered to be used for validating the fluid dynamical computer codes. The code generates a result in the form of vector flow field and this should be directly compared with experiment. Conventionally, any other physical quantities were computed from the resulted flow field and compared with the experiment. This, as including any integral operation, is an implicit validation, and insufficient.