Towards a 3D network model for indoor navigation

Indoor navigation is a fast developing area, but researchers are facing various challenges. One of them is the 3D model that could support the navigation. After reviewing current development of models for indoor navigation, in this paper we generalize essential emergency phases of buildings and clarify requirements for indoor navigation models. Then typical indoor navigation models are compared and their pros and cons are given. Based on these work, we propose a 3D network called “Indoor Visibility Structure”, which makes use of 3D geometry & semantics of buildings and allow for automatic generation of navigation network. The proposed approach is designed to resolve navigation in complex buildings. Ultimately, by relying on the IVS, its updating mechanism, and corresponding routing strategy considering indoor real-time changes, the ‘door-to-door’ navigation within buildings could be achieved. etc.) in the environment due to smoke, water, or other types of damages are represented only on the network for navigation. Thus, the link with the geometry of the building is disturbed and may lead to a loss of important information. For example, windows on the first and second floors, which are not normally included in the network for navigation, might be omitted as options for escape. This paper presents a new concept to navigation modeling, which makes use of 3D geometry & semantics of a building and allows for automatic generation of navigation network. Depending on the damages on the building different networks can be derived, i.e. taking into account different construction elements. The proposed approach aims at resolving navigation in complex buildings, by relaying on an Indoor Visibility Structure and a ‘door-to-door’ navigation within buildings. Following this introduction, section 2 summarizes the essential emergency phases of buildings, navigation requirements and evaluation criteria of indoor navigation models. Section 3 introduces several typical indoor navigation models and assesses these models. Section 4 provides a possible better solution for indoor navigation models, including navigation model design and routing strategy. Section 5 presents the conclusion of this paper. 2 REQUIREMENTS FOR INDOOR NAVIGATION MODELS While good for an emergency situation (e.g. fire, air pollution) a model and the corresponding system for navigation might be inappropriate for others (e.g. earthquake & flood). In case of flood usually the first floors are mostly damaged (i.e. escape to the upper floors is recommended), while in case of fire the upper floors might be more dangerous. It is never known which parts of the building are more secure, but estimates can be made on which construction elements (i.e. the semantics that is needed) might play a role in the navigation within buildings. 2.1 Buildings status in emergency situations Accurate information about the status of the building is one of the most critical aspects in successful navigation and evacuation. The conditions in the building change during an incident: stairs might be not accessible due to rubble or fire, exits might be unavailable due to high water level, rooms and corridors might be not recommendable due to smoke or gas leakage. Therefore, to make sure navigation models could be applied in all kinds of cases, it is necessary to classify the status of buildings in an emergency. We propose following classification: − Status 0. Normal state, no change within indoor environments (this is the everyday status). In this stage, elevators could be used, yet emergency exits of buildings cannot be open. Pedestrians can walk freely within the buildings. − Status 1. Some accidents occurs in buildings (e.g. on fire or gas leak), yet it causes no damage of main structure in this status. In this phase, normal and emergency exits may be opened, but elevators may not be used, etc. Evacuees could escape from the incident building according to evacuation instructions, following sound and light instructions. − Status 2. A certain detriment of indoor environments is obvious. Because the structure of buildings would be deformed or not accessible (e.g. smoke, water, etc.), some parts of the buildings will be shut-down. − Status 3. If it is the case, the disaster building is seriously damaged (might be collapsed floors). That means it is difficult to find an escape way for people in some isolated indoor areas. It is also barely possible for rescuers to enter the building. A scenario could be used to describe these Statuses: fire hazard happens in the 12th floor of a building with 30 stories. At first, the fire spread endangers several rooms in the 12th floor yet the staircases still can be used. Smoke from the fire has not disseminated too far. This scene could be considered as Status 1. In this case, elevators would be stopped while emergency exits would open. People can utilize passageways and safe exits for evacuation according to predefined evacuation plan.