# A Modified Methodology for Generating Indoor Navigation Models
## 2 Research Objective and Methods  
The aim of this study was to propose a new method for the automatic generation of indoor navigation networks based on the floor plan. The proposed method is easy to use, and it involves simple transformations of geometric data from floor plans. It should be noted that the proposed method was initially tested on cadastral data. The axis of a road lane was mapped based on road parcels [38]. During successive attempts, the corridor segmentation method was evaluated based on various sets of base points [37]. The method proposed in this study relies on a new approach to the segmentation of structures. The applied segmentation method minimizes the irregularity of segments by dividing space across corridors. According to [PERSON] and [PERSON] [39], the segmentation process should rely on points marking the vertices of partition walls. The method proposed in this study has been expanded to include new elements that minimize route zigzagging. The analyzed object was one floor of a building (Figure 1a). The network models generated with the use of classical methods, the NRS model (corridor-entrance), and the NMSE model (corridor-entrance-room) are presented in Figure 1b,c. The network models generated with the use of the NRS and NMSE methods are not suitable for navigation. Network edges intersect building walls at locations where traffic cannot exit the building (Figure 2b). The fragments of the network in corridor space have to be modified because they do not reflect traffic routes. In an attempt to propose a new method for generating navigation network models, the authors focused on solutions that generate routes in corridors and integrate these routes with the neighboring objects. A route was generated in corridor space based on a geometric relationship that is used to manually edit the axes of elongated objects (Figure 2a) in Geographic Information System (GIS). The middle line, such as a route, is plotted based on the midpoints [P\({}_{\text{Mid}}\)] of a zigzag line. A zigzag line should be based on the points located along the edges (corridor) of structure S, with at least two turning points on the boundary of structure S. Midpoints [P\({}_{\text{Mid}}\)] should be mapped based on sections (edges) of the zigzag  
Figure 1: The analyzed object (**a**) and topological models of indoor navigation networks based on Node-Relation Structure (NRS) (corridor–room) (**b**) and Node-Relation Structure and Entrance (NMSE) (corridor–entrance–room) (**c**). line located inside structure S (Figure 2a). To construct an axis in the NRS model, structure S should be segmented in such a manner as to ensure that segmentation [SS] intersects the building and that the midpoints of the zigzag lines [P\({}_{\text{Mid}}\)] are located within the segments [SS] (Figure 2b). Midpoints [P\({}_{\text{Mid}}\)] are the segment [SS] nodes. After data transformation, the object's axis can be generated automatically based on segments [SS] with the use of the NRS [4] method. This approach can be referred to as the Middle-Point Relation Structure Segment (MPRSS). The methodology for generating indoor navigation models [39] was modified. The Node-Relation Structure Segment (NRSS) method of generating a topological network based on nodes that are centroid segments was described in [39]. In the presented modification, midpoints [P\({}_{\text{Mid}}\)] are adopted as segment nodes. This minor change considerably influences the shape of the network. The MPRSS method of developing a network is described below. The MPRSS methodology makes a reference to the NRSS method, which is presented in [39].