  We study the estimators of various second-order weak lensing statistics such
as the shear correlation functions xi_\pm and the aperture mass dispersion
<M_ap^2> which can directly be constructed from weak lensing shear maps. We
compare the efficiency with which these estimators can be used to constrain
cosmological parameters. To this end we introduce the Karhunen-Loeve (KL)
eigenmode analysis techniques for weak lensing surveys. These tools are shown
to be very effective as a diagnostics for optimising survey strategies. The
usefulness of these tools to study the effect of angular binning, the depth and
width of the survey and noise contributions due to intrinsic ellipticities and
number density of source galaxies on the estimation of cosmological parameters
is demonstrated. Results from independent analysis of various parameters and
joint estimations are compared. We also study how degeneracies among various
cosmological and survey parameters affect the eigenmodes associated with these
parameters.
