Estimating transient detection efficiency in electromagnetic follow up searches

During the most recent LIGO-Virgo science run (Dec 17 2009 to Jan 8 2010 and Sep 2 to Oct 20 2010) multi-messenger searches were performed using several partner telescopes. This resulted in large data sets with images covering several square degrees of the sky. Analysis of these images is currently underway using a variety of different tools. We present an overview of these efforts, in particular the development of new tools which enable us to establish the efficiency for transient images in the fields. This is critical in establishing the sensitivity of gravitational wave and electromagnetic multi-messenger searches to the astrophysical signals we expect to be associated with gravitational waves.