Arbaeen is a movement of love and faith; it is a combination of intellect and emotion, blending these two elements seamlessly (
1). Arbaeen has several important aspects, including the culture of resistance, walking and health, politics, unity, solidarity, sympathy, and many other hidden and unknown layers, which highlight its multidimensional nature. This event can be categorized as a mass religious gathering, a term used to describe events where large numbers of people come together for a shared religious purpose. Such gatherings, like Arbaeen, are not only spiritual in nature but also have significant social, political, and logistical implications.
Each year, despite the restrictions on pilgrimage during the final days, there is a relative increase in the number of participants from around the world. This growth presents significant challenges for providing services to the pilgrims, particularly given resource limitations. One of the primary challenges is the limited geographic space available to accommodate the massive influx of people, creating logistical difficulties in managing such a large-scale gathering effectively. Therefore, the most important objective of this research is to assess the feasibility of using a photo-map or spatial photo map along the Arbaeen walking route to identify unused lands for the development of geographical space in future planning.
Arbaeen walks have many positive effects, fostering social solidarity, strengthening the sense of belonging and collective identity at different levels of the family, street, and neighborhood, and attracting the participation of social and religious groups, among others (
2).
Taleb Elm et al. analyzed the spatial quality of the Arbaeen Hosseini walking route based on the needs of pilgrims on the Najaf-Karbala route. They concluded that the Arbaeen walking route is safe enough and provides a suitable platform for social interactions, albeit with some limitations (
3).
Hadi and Abed researched multifunctionality as a tool to accommodate the needs of "Ziyarte Al-Arbaeen" visitors. Their results showed that multifunctional spaces can enhance the efficiency of urban areas during events with high densities (
4).
There are four land borders for entering the territory of Iraq, and the map of Iran's borders for Hosseini's Arbaeen, along with their distance to Karbala, is shown in
Figure 1 (
5).
One of the important and practical methods for investigating the extent of population surveillance is the use of field of view maps. The field of view refers to a geographical area that can be monitored and controlled from a specific location (such as an observation tower) and is also widely used in surveillance and military contexts. Therefore, understanding the areas under observation and surveillance control is of significant importance and necessity for this research. Bayn al-Harameen has been chosen as the study area or target community for this part of the research due to its strategically important location within the city, as well as its designation as the maximum population density line during Arbaeen. Thus, the importance of this research lies in achieving thorough monitoring during peak pilgrim population conditions. This issue has been addressed in this paper by providing a site selection map and conducting visibility analysis. In general, research conducted in the field of visibility analysis has utilized geographic information system (GIS) and related software. Jafarzadeh and Valizadeh Kamran combined GIS, remote sensing, and multi-criteria decision-making to locate military barracks in Ardabil city. They concluded that GIS is effective for identifying suitable locations for military barracks (
6). Ahmadi and Karimi Moshaver employed visual field analysis to evaluate the visibility of high-rise buildings. They concluded that visibility analysis is an effective tool for modeling visibility in the design of high-rise buildings prior to their construction (
7). Oroji et al. used visibility analysis in ArcGIS to evaluate the tourist field of view for geomorphosites in Qeshm Island Geopark. They found that the geomorphosites of the Valley of Statues, Chah Kouh Gorge, and Bam Qeshm had the best conditions for tourist visibility (
8). Ruzickova et al. proposed a new method for preparing field of view maps in GIS software by considering permeable obstacles and their effects. Their method facilitates the creation of field of view maps in various fields, including military, architecture, archaeology, and radio communication (
9). From the review of prior research, it is evident that visibility analysis is widely utilized in security and military contexts, as well as in other scientific fields such as architecture, geography, urban planning, and urban development.
1.1. Definitions and Concepts
The field of view, or viewshed, is the geographical area that can be seen from a specific location. This includes all surrounding points that are within the line of sight of that location, while excluding points that are beyond the horizon or obstructed by terrain and other features, such as buildings and trees. Conversely, it can also refer to an area from which an object can be seen (
10). A view is not necessarily limited to the visible spectrum for humans; it may include the invisible spectrum, such as radio and television waves.
These maps are widely used in military science, urban planning, and archaeology. With the help of a digital elevation model (DEM), the field of view or viewshed can be determined. This approach can be useful for locating telecommunications masts, observation posts, and similar structures. For example, if we examine Tehran's watershed from the top of Damavand Peak, the visible areas would appear as shown in
Figure 2 (
11).
Determining the field of view is one of the important applications of the digital height model (11)
In the above figure, the blue dots indicate the positions of the observers, and the colored areas represent the field of view for each observer. Scientists utilize field of view maps for various purposes, including military applications, telecommunication planning, and other scenarios where the field of view is critical (
12). For instance, in the United States, the following field of view map was used to determine the location of a proposed tower (
Figure 3) (
13). In this figure, the dark and shadowed areas indicate locations where the proposed tower would be hidden or not visible.
The shaded areas on the map show the areas outside the view of a proposed tower. The tower will not be visible in these shaded areas (13)
Viewshed or determining the field of view is created using one of two elevation models: Digital elevation model or vector (TIN) raster. This map is prepared by using one of these layers and specifying the point for which the field of view is to be calculated. In this analysis, a point is determined on the region's surface, and based on that, the visible regions are identified. Therefore, in addition to the elevation raster layer, a point layer is also required (
14).
Field of view maps are generally represented in two modes: (1) Visible areas, typically shown in green or as the number one {1} in raster space, and (2) invisible areas, usually shown in red or as zero in raster space. The colors are conventional; for example, non-visible areas may be left colorless, and only visible areas are shown in green, as in the field of view map discussed in this article.
Geographic information systems work with data related to geographic locations. In other words, GIS collects, produces, maintains, retrieves, and analyzes data that occupies space in the real world (
15). It is a computer-based system for managing and analyzing geographic information, capable of collecting, storing, analyzing, and displaying geographic data (National Geoscience Database of Iran).
Geographic information system is a location-based system that answers the key question of "where." For instance, where should an observation tower be built to maximize visibility, or which areas in a city are most suitable for constructing educational, military, or other facilities? Both active and passive defense strategies should be considered to fulfill its inherent duties. Consequently, optimal management is a key consideration within this system.
A raster consists of a set of points or cells that represent the features of the Earth's surface in a regular grid (
16,
17), addressed by their row and column numbers. The smallest unit in a raster is called a pixel or cell (
15). A digital elevation model is a type of raster that contains important elevation data. This data is essential for extracting field of view maps in GIS programs.
The earth's surface phenomena are perceived in three-dimensional (3D), making the simulation of landscapes a crucial goal of 3D models. The digital elevation model provides digital data used for preparing the topographic model of the earth's surface (
15).
Digital elevation models have specific applications in observational analysis, such as determining the visibility of features from a particular point and angle or identifying which effects will be visible in a specific direction (
15).