Research On Three-dimensional Data Model In Underground Environment Based On Nurbs

Three-dimensional data model is one of the important content of the3D(three-dimensional) geographic information system. The3D formation model represented by patches is the important respects of geological environment3D geographical information system. As polynomial surface and other surface manifestations of mathematical analysis cannot represent the complicated geologic situation accurately, and fitting surfaces may cause high fitting numbers hard to calculate, meanwhile the interpolation fitting surface will not reduce accuracy by pre-specified control points. The formation in film based on multi-TIN or multi-DEM not only has a great improvement on the model accuracy, but it brings vast amounts of data, resulted in a great restriction on data storage and analysis. With the considerations of the above issues, the dissertation proposes to use Nurbs(non-uniform rational b-spline surface) as the unified representation form of the ground surface model to bring into the formation three-dimensional data model, accordingly the good properties of Nurbs also introduced in.In this dissertation, main work includes the followings:(1) Based on the borehole data, the strata is stratified, and the stratifying methods and processes are presented.Tentative method has been proposed to use Nurbs surface model to represent underground environment three-dimensional data model as the unified representation form, Nurbs parameter surface is used to represent the spatial objects;(2) Several data interpolation encryption methods have been analyzed, and according to the interpolation results, it is proved that self-reflection fractal interpolation to borehole data has good results both in the horizontal and vertical direction, which is suitable for self-reflection fractal of strata itself, especially under the situation of the small data amount, and that the fractal interpolation can maintain the strata self-reflection fractal structure different from other, and the interpolation speed is also faster than others;(3) The formation three-dimensional surface model has been build, based on Nurbs (non-uniform rational b-spline surface), and by the way of building and testing the unified Nurbs model of spatial points, polyline and polygon, the dissertation proposed to use three parameter Nurbs entity model to represent entities, enabling Nurbs surface model to represent the object's internal according the Nurbs unified representation form, except representing the object boundary;(4) The Nurbs surface model is built, and the storage structure, along with the topology of various spatial object models are given;(5) The main calculating method of Nurbs formation model are given, focused on the Nurbs calculating process and method of surface length, area and volume, and experiments are carried out to check the calculating results;(6) The Nurbs modeling method of several special geological objects is given, and the modeling process and method of surface fractal texture, which can well represent the strata roughness and have excellent effects to represent strata surface, based on the analysis on the strata surface texture of the surface model;The dissertation has built the underground environment three-dimensional data model, which is based on Nurbs and its overall structure, modeling process and calculating are also given. Through the experiments it is proved that this model, compared with other models, reveals characters of simplicity, low storage and efficient operation.