  The most commonly used techniques for estimating the background contribution
in IACT data analysis are the ring background model and the reflected region
methods. However, these two techniques are poorly suited for analyses of
sources with extensions comparable to the detector's field of view (greater
than $\sim$1$^{\circ}$). Nearby pulsar wind nebulae, supernova remnants
interacting with molecular clouds, and dark matter signatures from galaxy
clusters are just a few potentially highly extended source classes. A three
dimensional maximum likelihood analysis is in development that seeks to resolve
this issue for data from the VERITAS telescopes. The technique incorporates
relevant instrument response functions to model the distribution of detected
gamma-ray like events in two spatial dimensions. Additionally, we incorporate a
third dimension based on a gamma-hadron discriminating parameter. The inclusion
of this third dimension significantly improves the sensitivity of the technique
to highly extended sources. We present this promising technique as well as
systematic studies demonstrating its potential for revealing sources of large
extent in VERITAS data.
