In last years, Simultaneous Localization And Mapping techniques monopolize research in mobile robot self-localization, especially in the civilian, Service Robotics domain. In this paper we argue that techniques derived from the industrial scenario, in particular beacon-based triangulation systems, should be taken into considerations even for civilian applications whenever we deem important to provide accurate, a priori specifications about the system behavior in a generic, yet untested environment. The paper provides an analytical expression of sensitivity to errors for triangulation depending on the system geometry.