  The least-action principle (LAP) method is used on four galaxy redshift
surveys to measure the density parameter Omega_m and the matter and
galaxy-galaxy power spectra. The datasets are PSCz, ORS, Mark III and SFI. The
LAP method is applied on the surveys simultaneously, resulting in an
overconstrained dynamical system that describes the cosmic overdensities and
velocity flows. The system is solved by relaxing the constraint that each
survey imposes upon the cosmic fields. A least-squares optimization of the
errors that arise in the process yields the cosmic fields and the value of
Omega_m that is the best fit to the ensemble of datasets. The analysis has been
carried out with a high-resolution Gaussian smoothing of 500 km/s and over a
spherical selected volume of radius 9,000 km/s. We have assigned a weight to
each survey, depending on their density of sampling, and this parameter
determines their relative influence in limiting the domain of the overall
solution. The influence of each survey on the final value of Omega_m, the
cosmographical features of the cosmic fields and the power spectra largely
depends on the distribution function of the errors in the relaxation of the
constraints. We find that PSCz and Mark III are closer to the final solution
than ORS and SFI. The likelihood analysis yields Omega_m= 0.37\pm 0.01 to
1sigma level. PSCz and SFI are the closest to this value, whereas ORS and Mark
III predict a somewhat lower Omega_m. The model of bias employed is a
scale-dependent one, and we retain up to 42 bias coefficients b_{rl} in the
spherical harmonics formalism. The predicted power spectra are estimated in the
range of wavenumbers 0.02-0.49h Mpc^{-1}, and we compare these results with
measurements recently reported in the literature.
