  Poloidal and toroidal velocities of fully-ionised carbon are measured by
means of charge exchange recombination spectroscopy (CXRS) in the TJ-II
stellarator. We present a detailed treatment of the 3D geometry and show that
flow measurements, performed at different locations of the same flux surface,
are compatible with flow incompressibility for the low density plasmas under
study (line averaged electron densities $\bar{n}_e\,\le\,10^{19}$ m$^{-3}$).
Furthermore, comparison with neoclassical calculations shows quantitative
agreement with the measured radial electric field and ion bootstrap parallel
flow in the absence of an external momentum input.
