and more recently the Unbiased Minimal Variance estimator (UMV)[@umv] are examples of methods developed to reconstruct the three-dimensional velocity and density fields from the observed radial component of the peculiar velocity. All methods assume that on the scales of interest the perturbations are small and non-linear effects can be neglected. The various methods have also been extensively tested using mock catalogs drawn from simulations that mimic the nearby universe.

Recently, the UMV method has been applied to the SEcat catalog of peculiar velocities and to the redshift survey data. Figure \[fig:mass\] shows the map of the PSCz galaxy density field (left panel) and the mass density field (right panel) along the Supergalactic plane, the latter obtained from the SEcat data using a Gaussian smoothing radius of 1200 . The main features of our local universe are easily identified in these maps, including the Great Attractor (GA) on the left and the Perseus-Pisces supercluster (PP) in the lower right. There is also a hint of the Coma cluster, which lies just outside the volume probed by SEcat, in the upper part on the map. The similarity between the mass and galaxy density fields is striking, especially considering the limitations to the 