# Geotechnical Property Modeling and Construction Safety Zoning Based on GIS and BIM Integration
## 2 Research Methods
### 3D Visualization, Management, and Soil Volume Calculation Using BIM  
This part integrates the digital geotechnical maps developed in the GIS platform with BIM to enhance the visualization of contextual GIS information and enrich each layer with semantic information. The geotechnical model in the BIM platform not only  
Figure 2: The explanation of kriging analysis employed in ArcGIS for spatial interpolation of geotechnical information. contains detailed geometry information about the underground soil but also non-geometric information. The non-geometric information such as soil type, angle of internal friction, alterberg limits, etc., with the 3D geotechnical soil model, increases its functionality and enables better control. Furthermore, the volume calculation of each type of soil available in the ground is determined, which is very significant for earthwork projects since it is involved in every construction project. GIS has been employed to develop a surface representation of the geotechnical information, which is georeferenced with the actual geographic coordinates integrating terrain and below surface information. The georeferencing of the BIM model is necessary before the incorporation of GIS information in BIM for the successful integration. The standard for the BIM model is industry foundation class (IFC), and it is possible to georeferenced IFC file [30]. The use of the IfcSite entity can be selected, which represents the location of the construction area. The coordinates of the real world can be stored in the RefLongitude, RefLatitude, and RefElevation attributes. The attribute longitude and latitude are integer values for degrees, minutes, and seconds, and, optionally, a millionth of seconds with reference to the world geodetic system WGS 84, while the elevation is measured with respect to the sea level. Furthermore, it has two more attributes that allow increasing the accuracy of the real-world coordinate to be assigned. The LandTitleNumber assigns a designation to the site within a regional system, and the SiteAddress assigns an address for postal purposes to the site. The model stores the geotechnical property model in the IFC structure. However, the IFC structure is very generic and contains a lot of information when exported. Therefore, model view definition (MVD), which is a subtype of IFC data containing limited information that can be used for a specific purpose. Based on the latest version of IFC (IFC 4x3), the paper uses IfcGeotechnicalAssembly, which is the subtype of IfcGeotechnicalElement; the abstract concept for the representation of the geotechnical or geological properties. As the paper presents the geotechnical information in the form of a borehole, which is the linear profile of soil information, surfaces that present the geotechnical information along the whole area based on the interpolation of borehole point information, and solid representation containing the volume of the geotechnical model based on the surface-to-surface volume calculation. The IfcGeotechnicalAssembly has three subtypes; including, IfcBorehole, IfcGeomodel, and IfcGeoslice. The linear feature of the borehole can be represented with the use of the IfcBorehole. Furthermore, the IfcGeomodel and IfcGeoslice are utilized for the surfaces, sections, and solid (volumetric) representation. The hierarchical representation of the entities that have been used in this for the representation of the geotechnical information is illustrated in Figure 3.  
The BIM tools such as Autodesk Civil 3D supports the georeferencing information required in the IFC file to set the world coordinate system (WCS). The GIS surface information can be integrated with the help of such tools to visualize the geotechnical surfaces in the BIM environment. The BIM model provides accurate and more detailed information about soil geotechnical information in three-dimensional. It is also possible to calculate the volume of each type of soil in the BIM using the surface-to-surface method.