  We present here a simple construction of a wavelet system for the
three-dimensional ball, which we label \emph{Radial 3D Needlets}. The
construction envisages a data collection environment where an observer located
at the centre of the ball is surrounded by concentric spheres with the same
pixelization at different radial distances, for any given resolution. The
system is then obtained by weighting the projector operator built on the
corresponding set of eigenfunctions, and performing a discretization step which
turns out to be computationally very convenient. The resulting wavelets can be
shown to have very good localization properties in the real and harmonic
domain; their implementation is computationally very convenient, and they allow
for exact reconstruction as they form a tight frame systems. Our theoretical
results are supported by an extensive numerical analysis.
