  In this paper we discuss several methods of significance calculation and
point out the limits of their applicability. We then introduce a self
consistent scheme for source detection and discuss some of its properties. The
method allows incorporating background anisotropies by vetoing existing small
scale regions on the sky and compensating for known large scale anisotropies.
By giving an example using Milagro gamma ray observatory we demonstrate how the
method can be employed to relax the detector stability assumption. Two
practical implementations of the method are discussed. The method is universal
and can be used with any large field-of-view detector, where the object of
investigation, steady or transient, point or extended, traverses its field of
view.
