redshift surveys worth mentioning in the present context is that involving galaxy samples extracted from the [*IRAS*]{} survey such as the 1.9 Jy[@strauss1.9], the 1.2 Jy[@fisher1.2] and the  [@saunderspscz] redshift surveys. While sparsely sampling the galaxy distribution, these surveys provide a sky coverage unmatched by optical surveys. This all-sky coverage allows a more reliable determination of the gravity field induced by fluctuations of the galaxy density field which can be compared to the measured peculiar velocity field to estimate the parameter $\beta$.

From the above discussion, it is clear that by themselves redshift surveys are more useful for studying the properties of galaxies than as cosmological probes. However, combining them with redshift independent distances to map out the peculiar velocity field of galaxies and to predict the peculiar velocity field from galaxy density fluctuations provide powerful tools to probe the nature of the matter distribution and its relation with the galaxy distribution.

Mapping the Peculiar Velocity Field {#zv}
===================================

The radial component of the peculiar velocity is given by $$U = cz - d$$ where $d$ is an estimate of the galaxy distance derived from a secondary distance indicator. Most of the available samples rely on the TF and Fundamental 