  (Abridged) Weak gravitational lensing induces distortions on the images of
background galaxies, and thus provides a direct measure of mass fluctuations in
the universe. Since the distortions induced by lensing on the images of
background galaxies are only of a few percent, a reliable measurement demands
very accurate galaxy shape estimation and a careful treatment of systematic
effects. Here, we present a study of a shear measurement method using detailed
simulations of artificial images. The images are produced using realisations of
a galaxy ensemble drawn from the HST Groth strip. We consider realistic
observational effects including atmospheric seeing, PSF anisotropy and
pixelisation, incorporated in a manner to reproduce actual observations with
the William Herschel Telescope. By applying an artificial shear to the
simulated images, we test the shear measurement method proposed by Kaiser,
Squires & Broadhurst (1995, KSB). Overall, we find the KSB method to be
reliable with several provisos. To guide future weak lensing surveys, we study
how seeing size, exposure time and pixelisation affect the sensitivity to
shear. In addition, we study the impact of overlapping isophotes of neighboring
galaxies, and find that this effect can produce spurious lensing signals on
small scales. We discuss the prospects of using the KSB method for future, more
sensitive, surveys. Numerical simulations of this kind are a required component
of present and future analyses of weak lensing surveys.
