Research On Three Dimensional Cadastral Spatial Data Model And The Related Key Technology

Cadastre is a tool which is used to manage national land resources and assets.Traditional cadastre is two-dimensional one which takes parcel as basic management unit to administer land surface rights, and its theoretical basis is consistency of the right nationality of the same parcel in the vertical direction, namely the ownership rights of underground, surface and ground space belong to the identical obligee. In traditional cadastre, parcels may not overlap and gaps may not occur (forming a planar partition), which can ensure completeness and consistency. So far, two-dimensional cadastral concept has been serving land management domain more than centuries and playing vital roles in social managements and economic activities. However, real estates such as land and property in the real world are three-dimensional, this also suggested that cadastre should be three-dimensional.Due to the backwardness of the past economic development, land use mainly concentrated on the two-dimensional surface and it isn't necessary to extend land use into the third dimension. Therefore, traditional two-dimensional cadastre which takes surface right as core can satisfy social demands well. In recent decades, the rapid increase in population and intensified urbanization make the land use of urban areas, especially business centers under rising pressure. In order to provide more available space, the city development extends unceasingly to the third dimension.Many three-dimensional right entities such as buildings with distinctive styles, skyscrapers, multi-purpose buildings, underground parkings, air-defense projects, underground transport infrastructure, communication facilities and pipeline facilities etc. have been extended from surface into underground and ground space in urban areas. Three-dimensional land use makes the subject of property become pluralism in the vertical direction,namely underground, surface and ground space can be stratified development and are distributed to different obligees.Tendency of Three-dimensional land use brings forth challenges to traditional land management theories and methods.Traditional cadastre mainly records two-dimensional land surface information.As far as the exploiting situation in three-dimensional space is concerned, it usually projects three-dimensional right entities (such as buildings) onto the two-dimensional land surface and uses projected two-dimensional graph to represent its scope. In order to assist registeration, the third dimensional information is recorded into some attribute fields such as floor number,unit number, basement etc.This management scheme is suitable for land use pattern based on surface as well as buildings with relatively simple structure.However, if underground, surface and ground space of the same parcel separately belong to different obligees and land use situations are extremely complicated, when three-dimensional right entities are projected onto a plane,which would be bound to cause staggered overlapping of ownership borders and easily lead to legal disputes. Therefore, it is urgent to resort to three-dimensional cadastre to solve those issues.three-dimensional cadastre is a cadastre which registers and gives insight into rights and restrictions not (only) on parcels but on three-dimensional property units.Research on three-dimensional cadastre can greatly facilitate and perfect three-dimensional land-related management systems, institution and mechanisms, normalize land and property registration system,reduce real estate registration disputes, improve government efficiency and image of public service and have significant social significance. Three-dimensional cadastral study can be carried out at three levels:legislation, management scheme and technology.In this paper, we mainly study its technical aspect. Related research is as follows:(1) definition and representation of property volumeJust as two-dimensional cadastre taking parcel as basic unit and research object, three-dimensional cadastre also needs a kind of basic unit like parcel to expand relevant three-dimensional cadastral work.This kind of basic unit is called property volume in this paper.We will take right entities such as land and property as basis, use right space as reference, analyze the characteristics of land and property and give the definition and representation of property volume.(2) three-dimensional cadastral spatial data modelAfter given the definition and representation of property volume,the further work is to study how to abstract all types of property volume such as apartment unit, Skip-Floor apartment, semi-basement unit, underground garage as well as those very irregular property unit with curved surface in real world and use geometric solid such as point, line, face and body to model and represent them.However, owing to the diversity and complexity of property volume,the process that abstracts boundary mark, boundary line, wall and floor of various types, and other ownership units to geometric solid of geometric model is not a simple map relationship, but a complex constructing and modeling process. It not only needs to involve geometric model of the modeling object but also maintains topological relationship between geometric entities of various types.Therefore, we need to choose appropriate geometric and topological model to accurately simulate and represent three-dimensional cadastral entities in real world. In addition, three-dimensional cadastre is a multi-purpose cadastre which not only need to represent the spatial shape of property volume but also to support related spatial analysis and calculation.In view of these two aspects,we establish a hybrid model which integrates advantages of facial and volumetric model.The model which we have established not only fits the representation of geometric shape of property volume but also supports the needs of three-dimensional cadastral spatial analysis and calculation.(3) realized foundations and algorithm of three-dimensional cadastral spatial data modelThe three-dimensional cadastral spatial data model which we have established adopts boundary representation model to represent the shape of property volume and use irregular tetrahedral network (TEN) model to achieve three-dimensional cadastral spatial analysis and calculation.TEN is promotion of TIN in three-dimensional space and is three-dimensional homogeneous simplicial complex.In order to implement integration and transformation of these models,we have studied related theories of simplex and simplicial complex as well as generating algorithm of TEN and achieve mutual conversion of boundary representation model and TEN.(4) three-dimensional cadastral spatial analysis and calculation based on TENIn this paper,we adopts TEN as spatial analysis and calculation model.TEN is a collection of tetrahedron.In order to achieve the model, geometric parameters as well as three-dimensional analysis algorithms based on tetrahedron is explored.(5) three-dimensional cadastral experiment systemIn order to verify the feasibility and effectiveness of established model and related algorithms, we build a prototype system. In this system, we focus on the algorithms of three-dimensional data acquisition, three-dimensional object reconstruction technology, three-dimensional data generation and automatic re-build of regular property volume, division and merger of property volume, constrained Delaunay tetrahedral mesh generation of property volume and give test results.