The arrival direction distribution of cosmic ray particles observed on Earth is shaped by the cumulative effects of their galactic source locations and of trajectory bending in the turbulent interstellar magnetic field. Coherent magnetic structures are expected to disrupt particle trajectories and their observed distribution, as well. The heliosphere, the large magnetic bubble generated by the sweeping effect of solar wind on the local interstellar plasma, strongly affects the TeV cosmic ray particles detected on Earth. By unfolding the heliospheric influence on the observed anisotropy, it is possible to determine the pitch angle distribution of cosmic rays in the interstellar medium. This information makes it possible to study in detail the global diffusion properties of TeV cosmic rays in the Galaxy. However, observational blindness to key features of the cosmic ray arrival direction distribution may lead to biases in the determination of the heliospheric influence and of the interstellar CR distribution. Any inference of galactic TeV CR diffusion properties must carefully account for local propagation phenomena and observational limitations.