Research On 3D Modeling Of Farmland Shelterbelt,Road And Ditch With Parametric Methods

With the development of computer technology from aided cartography to aided design,the concept of parametric design has been deeply rooted in people's hearts,and related technologies have been widely applied in the fields of architecture design and urban planning.In the paper,the theory and method of parametric design were introduced to land consolidation planning and design.According to the features of objects in agricultural and forestry scenes,a parametric modeling method suitable for agricultural and forestry engineering objects was proposed.Roads,irrigation canals and shelterbelts in land consolidation planning are closely connected with the surrounding environment.It is difficult to design the whole scene comprehensively based on separately designed individual projects.With the help of 3D GIS technology,designers can not only integrate real data from various sources to quickly design optimized planning scheme,but also make full use of the analysis function of GIS for data analysis.The modelling of field roads,irrigation canals,farmland shelterbelt were mainly studied in this paper.(1)To solve the problem of inefficiency in the progress of formulating land partitioning plans,an approach for automating land reallocation based on binary search and Delaunay triangulation was proposed.Firstly,the Minimum Bounding Geometry(MBG)of a block was generated and triangulated by Delaunay triangulation.Secondly,the area of the triangles was added one by one until the accumulated area was close to the contract area(with an error less than±5%).Then change to the BS method to further decline the area error.Finally,iterate the progress to the rest part of the block then to other blocks until all blocks were partitioned and the land pre-distribution plan was generated.The feasibility of the algorithm was validated by taking the land consolidation project in the study area as an example.Three criteria(efficiency,area error and parcel shape index)were used to evaluate the results.Compared with the BS method,the time consumption of the BS-DT method decreased by 29.3%,while area accuracy improved by 28.2%and shape regularity improved by 18.2%.And each sub block had good accessibility to road or ditch due to the algorithm's control of the divide direction.Case study showed that the proposed BS-DT method could meet the demand of automatically developing and dynamically adjusting a land allocation plan.(2)According to the characteristic of crisscrossed field road network,a parametric modeling method based on GIS data was proposed.With vector road centerline as plane linear data and field road design norms and standards as knowledge rules,the automatic modeling of field road network was realized.Firstly,curved field roads were fitted by curves.Secondly,the intersection points were extracted from the road central line,intersection model was generated by the center line translation method according to road structure and road parameters.Finally,by seamless integration of road network model and terrain based on terrain editing,a unified model was formed.Case study showed that the parametric modeling method has the advantages of flexibility and high efficiency.By using this method,a three-dimensional field road network which in accordance with engineering specifications could be quickly established.(3)According to the feature that irrigation canal network involves various section type,a 3D modeling method based on parameterization was proposed.Firstly,based on canal centerline and cross-sectional parameters,single canal model was generated by cross-sectional lofting method,and canal intersection was generated by center line translation method.Secondly,upper and lower canals were combined together by model operation.Finally,canal models ware seamlessly integrated with surrounding terrain based on terrain editing.The goal of designing and displaying of 3D canal model network with various cross-section type in real coordinates were realized,and the problems of canal intersection,branch and separation from terrain were solved.Case study showed that the parametric modeling method can build 3D scene based on real geographic data,which improves the efficiency and accuracy of modeling.(4)In view of the difficulty in automatic modeling and 3D display of farmland shelterbelts in the process of planning and design of farmland shelterbelt,a method of automatic configuration of farmland shelterbelts based on model base was put forward.Constraints formed by the layout of roads,canals and parcels were imported into a rule base,and the automatic configuration algorithm of belt or block shelterbelts according to the rules was designed.By building a vegetation model base,random configuration or configuration according to certain rules of farmland shelterbelts was realized.Case study showed that shelterbelts modelling based on model base and rule base is beneficial to improve the standardization and efficiency of the configuration of farmland shelterbelt.