One of the most important services in mobile environments is Location Based and orientation aware services. Mobile Geo Information System (MGIS) users by using of various ways can interact with physical objects. One of this ways is pointing. In this study, by similar manner we want to use mobile devices as a pointer for obtaining information from buildings. It has recently been studied by researchers for specific purposes, but in most of their researches making true target is not investigate or they use heavy process to do this. Elements of ambiguity in selecting true target, is one of the most important problems that ought to be monitored. To deal with mentioned problem, first we classified the ambiguity into two categories. The first type occurs when selected buildings in pointing line are more than one. In this regards, we consider some kind of contextual information. These contexts consist of: user interest land use, proximity of current user position to position of buildings, point in polygon concept. Besides, we develop a method so called space digitizing based on drawing simple geometry shape of buildings. The other kind of ambiguity occurs when the intersect position of pointing line and building’s edge, is on the boundary of those buildings. We proposed probabilistic method to overcome this kind of ambiguity.In order to implementing above objectives, an application for mobile devices with Android operating system has been developed. By implementing this in K.N.Toosi University of Technology faculty of Civil and Survey Engineering, the correctness of application functionalities has been confirmed.