Faculty of Civil Engineering Institute of Construction Informatics, Prof. Dr.-Ing. Scherer Institute of Construction Informatics, Prof. Dr.-Ing. Scherer Technische Universität Dresden GIS 1 Geo Information Systems Part 2 Data Model Prof. Dr.-Ing. Raimar J. Scherer Institute of Construction Informatics Dresden,

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 2 Data Model: Geo Object In GIS all information which is managed is related to space-based objects. Each object is a concrete physical, geometrical or rational semantically constraint entity of the nature. It owns a very individual identity, namely his location. This gives each object his uniqueness. All similar objects, i.e. owning the same attributes, but each with a different location can be subsumed to an object class. A Geo Object is defined by 1. object class and 2. location (projection) on the earth surface remaining problem: TIME dependency Time dependency is modeled either on ● attribute level := attribute → record ● object level, i.e. Geo Object is defined by 3. time stamp Standardized data model GML Geography Markup Language standardized by OGC Open GIS Consortium Inc,

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 3 Data Model Object class Object Geometry Metric Vector or Raster Themes (Attributes) Graphical Representation Theme 1 Theme 2 … Theme n Topology ID

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 4 Data Model: Geometry Geometry (2D): only x,y = planimetric (2D + 1D): x,y + z (only digital terrain is 3D, all other elements are not) (2,5D): x,y + z being stored as an attribute for each object (1) (3D): x,y,z sufficient dense -edge model or wire model (e.g. isoline model) -surface model -body model (volume model) Classification of GIS regarding to types of geometrical representation: (4D): x,y,z,t (1) this may be sufficient for densily populated areas, where a lot of sufficiently small objects are stored in order to derive the digital terrain or

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden D D+1D D 525 3D Edge Model 3D Surface Model 3D Body Model Data Model: Geometry

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 6 Data Model: Topology Topology 0 cell point (node) 1 cell edge (model) 2 cell surface (model) 3 cell volume/body (model) or A A A A B B B C C D D E F G H

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 7 Data Model: Themes Themes 0 D : no theme 1 D : number of themes... n D 2 D Themes can be: real estate register age of people dears per square km sunshine hours per day (mean in July between ) CO 2 rate at days with: temperature above 20 degree and cloudy and.....

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 8 Data Model: Geometrical Model :Vector Data Basic element: Vertex Vertex-Line-Area-Volume logical data structure unique object ID vertex-oriented acquisition -> intensive acquisition time small amount of data needed for each object topological Information transparent representation possible -> presentation of several topics possible MIMI a2 a1 a3 V3 V2 V1 V4 L1

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 9 Data Model: Geometrical Model : Raster Data Basic element: Pixel only plane representation possible structuring only according to x,y location no object with a meaning no separate object ID (ID = location) no transparence simple data acquisition:scanning (=cheap) huge amount of data (=expensive to manage)  usually used as background (information) representation GIS is optimized to manage combination of raster and geometrical objects)

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 10 Data Model: Geometrical Modelling Methodes: analytical approximative: e.g. splines, poligons Information: metric topological Models: Edge model (wire model) E=E(V) Surface modelS=S(E,V) Body model (volume model)B=B(S,E,V) V=Vertex

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 11 Data Model: Requirements Universe of discourse =  Objects (scope of definition) Scope of values completeness = min needed attributes uniqueness = only one internal representation (but several external repr.) efficiency = depends on complexity of used algorithms (computing time, memory requirements)  efficiency can only be achieved through specialized application

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 12 Data Model: Geometrical Model Types parametric representation enumeration methods (voxel) -> for intersection with raster data cell decomposition (cell = simple blocks with meaning/content) boundary representation constructive solid geometry

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 13 Data Model: Parametric representation The parametric representation characterizes each element of the object family by a fixed number of parameters such as length l, width w, hight h, depth d, radius r, angle a M II MIMI a h c b The combination of these param. objects can be done by using the set theory. The parametric object has a meaning such as roof, wall, column, slab, … This data model is used in AEC (Architecture, Enginering and Construction) and named IFC (Industry Foundation Classes) standardized by the IAI (Internat. Alliance of Interoperability),

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 14 Data Model: Aggregation Method M II M I1 Example: Decomposition of the house In the IFC, the parametric object are more granular, like wall, beam, window. The can be subsumed e.g. to a story and the story can be represented by a bounding box, which result in the above presentation, for instance. A standardized interoperable interface between GIS data IFC is still missing. Propietary interface are offered e.g. by AutoDesk and Grahpisoft

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 15 Data Model: Boundary Method M II MIMI a2 a1 a3 t1 Description of the decomposed elements of the house by the geometrical method of boundery representation

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 16 Data Model: Enumeration methods The enumeration method (spatial occupancy enumeration) defines a 3D object by using a set of uniform space cells. If a box is decomposed to 2 3k element cubes, the resulting octogon tree is a possible representation. In plane the pendant of the octogon tree is the quad tree which is often used in geo-information systems for data organisation ffffffff R W W ff f f eeee f=full, e=empty R=roof body, B=base body B W W

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 17 Quadtree decomposition Position code of 32: 3,2

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 18 Quadtree decomposition Vertexfree Pixeloccupied Pixel Example Showing the link to pixel representation

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 19 Data Model: Queries geometric query space = f(representation type) 1-D query: related to z – coordinate 2-D query: pos-bounded, inventory x,y 2-D + 1D: combination of 2-D and 1-D 3D: related to space x,y,z 4D: x,y,z,t

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 20 Examples of geometrical queries The natural surface is given in boundary representation, while buildings are available in parametric representation. The following queries are possible: 1)Which parcel border points are located in the intervall between 200m and 250m above sea level (NN) ? 2)Which parts of the houses (garages) are part of border lines? 3)Identify all double garages, i.e. parts of houses with a>2.5m 4)Show all parcels, whose width b<25.00m 5)What is the volume in m³ of house No. 25? 6)Compute the Site occupancy index of parcel )Is the ridging of house No. 25 below or above m NN. 8)Identify all houses whose eaves is higher than c=3.0 m

Institute of Construction Informatics, Prof. Dr.-Ing. Scherer GIS Technische Universität Dresden 21 Data Model: Topological Model Topology = Theory of geometry of the location (of objects) shows the arrangement and the relationship = geometry without metric Topology is usually represented as graph Example Real estate plan A1 A3 A6 A2 A5 A7 A11 A9 A4 A8 A10 A12 R11R12 R22 R21