  In recent years a plethora of future surveys have been suggested to constrain
the nature of dark energy. In this paper we adapt a binning approach to the
equation of state factor ``w'' and discuss how future weak lensing, galaxy
cluster counts, Supernovae and baryon acoustic oscillation surveys constrain
the equation of state at different redshifts. We analyse a few representative
future surveys, namely DES, PS1, WFMOS, PS4, EUCLID, SNAP and SKA, and perform
a principal component analysis for the ``w'' bins. We also employ a prior from
Planck cosmic microwave background measurements on the remaining cosmological
parameters. We study at which redshifts a particular survey constrains the
equation of state best and how many principal components are significantly
determined. We then point out which surveys would be sufficiently
complementary. We find that weak lensing surveys, like EUCLID, would constrain
the equation of state best and would be able to constrain of the order of three
significant modes. Baryon acoustic oscillation surveys on the other hand
provide a unique opportunity to probe the equation of state at relatively high
redshifts.
