Research On 3D Visualization System Of Outdoor Pressure Pipeline Based On RTK Positioning

Outdoor pressure pipelines are essential parts in the development of modern urban infrastructure.But most systems don't have an unified database of pipeline geographic information owing to the coexistence of multiple pipeline inspection methods.The existing 3D pipe-network visualization system is mostly secondary development by model library plug-in unit or GIS system,and users need to load third-party plug-in units during usage,resulting in poor coupling of pipe-network models and low connectivity.Furthermore,the system is not cross-platform.Currently,outdoor pressure pipeline management in Huzhou City still adopts the traditional manual drawing management.And the realization of 3D visualization system management can make a significant contribution to pipeline engineering application management.Therefore,the study takes some pipelines in Huzhou City as an example,and use RTK system to collect outdoor pressure pipeline data.Subsequently,the data is stored in the library for unification to construct the pipeline network topology.And 3D pipeline model is constructed by mathematical method with high articulation accuracy,realizing the automatic modeling.3D visualization system of outdoor pressure pipeline is designed and implemented based on 3D visualization technology with plug-in free and cross-platform,realizing 3D management of outdoor pressure pipelines.Main working contents are shown below:(1)The RTK system is used to acquire 3D data of outdoor pressure pipelines.Plane rectangular coordinate is converted from latitude and longitude coordinate by Gaussian projection principle,and then is converted to true plane coordinate by four parameters,which combines with the elevation data to obtain 3D data of outdoor pressure pipelines,providing data support for system.(2)The pipeline is simplified and the system only consists of pipeline sections and pipeline points.The modeling methods are proposed for straight pipeline sections and different pipeline points as follows.Including: The modeling of the straight pipeline section is completed by solving the coordinates of the starting and ending points of the fitting circle;the modeling of the bend is achieved by finding the centerline of the bend,then combining the centerline fitting points to construct the section circle,and connecting the section circles to the corresponding points in turn;It is realized by using circular table articulation at the reducer point;the ellipse generated by the orthogonal formation of straight pipeline segments is used to divide the four-pass point into four pipeline segments to find out the coordinate values of the two orthogonal ellipses,and to complete the drawing of the pipeline sections with reference to the direction of the circular cross section,so as to complete the modeling of the four-pass point and the three-pass point.(3)The 3D visualization system of outdoor pressure pipeline is realized.With 3D visualization technology of Web GL and Three.js,JSON data format of 3D pipe-network model is parsed through the browser side,and the user can load 3D pipeline model,operate the pipeline rotation,translation,scaling and 3D pipeline data extraction in the browser side to meet the user interaction requirements.Meanwhile,3D pipe-network management is realized,which manages the basic data,pipeline attributes,and affiliated units,pipeline log information as well as system users,forming a 3D pipe-network management model.In summary,3D pipeline model based on 3D data of outdoor pressure pipelines collected by RTK positioning,combined with the mathematical method,can solve the problem of unsmooth model articulation.Meanwhile,3D visualization system of outdoor pressure pipelines,realized based on the B/S architecture,provides convenience for pipeline management users,which can analyze outdoor pressure pipelines in an accurate and efficient way.