Indoor Navigation Graph of the Historical Covered Bazaar of Tabriz Based on IndoorGML Standard

Many users around the world use the services of pedestrian/vehicle navigation systems. Due to the design and construction of large and complex structures, wayfinding in buildings is also very important. Indoor spaces elements (such as rooms, corridors, walls, doors, elevators, etc.) are different from the outdoor spaces elements, so the first step of indoor navigating is extracting the navigation graph of these spaces. The graph obtained from the interior spaces has various criteria because of the variety of factors affecting the pathfinding of individuals. Therefore, the collection and assignment of these criteria to the navigation graph are necessary which based on the characteristics and interests of each user. The aim of this study is to extract the navigation graph of the historical covered bazaar of Tabriz city and routing in it. The UNESCO recognizes Tabriz Bazaar as world heritage site in 2010. This bazaar has 20 rastes, 35 saras, 25 timches, 11 dalans, 9 religion schools, 8000 shops, and 40 types of jobs. Some places such as mosque and hoseyniyes are special places for Iranian bazaars, which are places for traditional and religious ceremonies. This Bazaar was located in the central part of the Tabriz city and has linear structure. In other words, the present study addresses two important issues in the field of indoor navigation. The first issue is the production of indoor navigation graphs for one of the most complex indoor space in the world, the historical covered bazaar of Tabriz city, based on IndoorGML standard principles. The second issue is the collection of criteria for this graph in order to navigate disabled people and routing them. IndoorGML is an OGC standard for an open data model and XML schema for indoor spatial information. It aims to provide a common framework of representation and exchange of indoor spatial information. The goal of this standard is therefore to define a framework of indoor spatial information to locate stationary or mobile features in indoor space and to provide spatial information services referring their positions in indoor space, instead of representing building architectural components. IndoorGML is intended to provide the following functions; 1) Representing the properties of indoor space, and 2) Providing spatial reference of features in indoor space. Connecting indoor and outdoor spaces is an important requirement of indoor spatial information. IndoorGML provides the concept of anchor node to connect indoor and outdoor spaces. Every indoor space contains at least one entrance, and it can be used to connect indoor and outdoor spaces. In IndoorGML, entrance is represented as a special node of topological graph in indoor space. We call it anchor node, which differs from other node in topological graph, since it may include additional information for converting indoor CRS (Coordinate Reference Systems) to outdoor absolute CRS. The dual graph from the Tabriz bazaar’s plan was drawn then the obtained edges summarized and connectivity graph created. For Tabriz bazaar’s graph, 360 main edges with a length of 9226.77 meters and 312 nodes were extracted. Five criteria including length, width, slope, obstacle, and stair were collected for each edge thought field observations and were stored in the attribute table. Finally, wayfinding was assessed and was compared for ordinary users and wheelchair users. The results indicate that 43% of the edges are unsuitable and 7% of main segments of the bazaar are Inaccessible for wheelchairs.