# Detecting Underground Geospatial Features for Protection of Rights in 3D Space: Korean Cases
## 1 Introduction  
Land use is gradually becoming complex and diversified owing to rapid urbanization and overpopulation. This has resulted in increasing interest in underground space development as part of sustainable national land development and the creation of a pleasant environment [1; 2; 3; 4; 5; 6; 7]. In general, underground space refers to the space beneath the surface of the ground where essential infrastructure, necessary for our daily life, is normally located. This includes subways, walkways, roadways, shopping centers, water and sewage facilities, as well as electricity, gas, and communication facilities [8; 9].  
However, a more realistic and concrete definition is required, as the former abstract definition makes it virtually impossible for humans to use the underground space located under the surface indefinitely [10]. Accordingly, the American Underground Space Association (AUSA) defines it as a spatial resource of a certain scale that is naturally or artificially created under the surface of the earth within the range that can be used for a purpose [11]. With reference to this definition, it is defined as a spatial resource of a certain scale that is naturally created or artificially created under the surface of the earth within the range of economic use, and when facilities for a certain purpose are added to this space, it is defined as an 'underground facility' or 'underground facility space' [12; 13]. The underground space covered in this study is an underground shopping center for the passage of citizens and commercial activities, which belongs to the 'underground facility space' of artificially built spaces.  
An underground space refers to a space that is symmetrical, with the ground space centering around the surface of the earth. In the cadastral field that involves the registrationof land, the concept of the 3D cadaster was introduced to efficiently manage and utilize the national territorial space [14; 15; 16]. A '3D cadastral system' is defined as a system that still registers rights and limited rights on 2D parcels but also gives more insight on the juridical and factual situation above and under the surface in case this is relevant with respect to legal security [17].  
In this study, a technique to register an underground shopping center space and individual store spaces in relation to the above-ground parcels is proposed. Previous studies and the current management and operation system of the underground shopping center are considered. Existing studies have mostly generated underground spatial information via surveys or field investigations. However, in terms of establishing the rights relationship, only the concept of underground spaces and the general directions for establishing rights relationship were investigated.  
In this study, in addition to conduction of a survey, existing public data are used to generate individual object-level underground spatial information. This study is different from previous studies in that the data used to generate the physical status and rights status information of the ground parcels, as registration information, are also used to establish property rights in the underground space. The attribute information required for the registration is also obtained.  
The rest of this paper is organized as follows. Section 2 introduces the research methods, equipment, and data used to generate the underground spatial information. The generation of the 3D underground spatial information is presented in Section 3, whereas Section 4 describes how to register the underground information. Lastly, a summary of the main conclusions of this study is presented in Section 5.