# Urban Geological 3D Modeling Based on Papery Borehole Log
## 1 Introduction  
The borehole log is a kind of comprehensive geological diagram, which can be used for the description of the stratum name, stratum thickness, lithology characteristic, geological structure and contact relationship, groundwater sampling and testing, borehole structure and drilling situation of strata. The borehole log is a basis for analyzing engineering-geological conditions and drawing geological maps. As an important reference for visualization of underground exploration information, the borehole log plays an important role in the analysis and decision-making of various underground projects.  
The three-dimensional model of urban geology, built based on borehole data and other survey data, can intuitively show the geometry, physical properties, and interrelationships of objects in the underground space, so it can be used as an integrated carrier of geological resources and environmental big data. Comprehensive analysis based on 3D geological model objects and their associatedattributed information has great advantages in the monitoring of urban geological environment and the development and utilization of underground space.  
Papery borehole data is the basis for constructing a three-dimensional urban geological model, and it is also the basic reference for constructing geological resources and environmental monitoring and pre-warning systems and formulating a comprehensive urban geological survey plan. In the past practice, manual data collection from paper documents was required to complete the extraction of borehole information. Due to the diversity of borehole sources and different standards for stratigraphic divisions, before borehole data can be used for 3D geological modeling, a standard stratum comparison table must be developed in advance according to the geological conditions in the local area. Even if the borehole data is standardized according to the table, and the boundary points of the stratum exposed by the borehole are interpolated, the resulting geological model often conflicts with geological knowledge and needs to be continuously revised in the later stage. This traditional 3D modeling method of urban geology based on papery borehole log has disadvantages such as high error rate and low efficiency.  
To improve the utilization efficiency of papery borehole logs and make the results of 3D geological modeling more reasonable, this paper proposes a method for quickly and intelligently recognizing and processing papery borehole log information and optimizing the modeling process after repeated analysis and practice. On the one hand, this method can quickly extract information from the papery borehole log, and fill and replace the data with lower confidence rates in it to improve the efficiency. On the other hand, it can integrate geological knowledge into the modeling process, pinch-out and faults caused by data errors are reduced, and the rationality of the 3D geological model is improved. The feasibility and effectiveness of the method were verified by applying this method to the practical link of 3D modeling of urban geology in Xinyang.  
In Section 2, this paper describes the related research work of papery borehole data extraction and geological knowledge fusion modeling process. The construction flow of 3D urban geological model is introduced in Section 3. In Section 4, this paper introduces the process of automatically extracting information from a papery borehole log, standardizing it into a database, and processing it into geological spatial data that can be used directly. In Section 5, this paper describes the integration of geological knowledge to optimize the 3D geological modeling process based on the existing geological maps, to obtain a reasonably usable 3D geological model. In Section 6, this paper shows the experimental results in the 3D modeling of urban geology in Xinyang by using the method proposed in this paper. In Section 7, conclusions and suggestions are put forward for future improvement.