4 Spaghetti Vector Data Model Each point, line, or polygon is stored as a record in a file that consists of that entity’s ID and a list of coordinates that define geometry.For Points:ID Coordinates3,45,521
5 Spaghetti Vector Data Model Each point, line, or polygon is stored as a record in a file that consists of that entity’s ID and a list of coordinates that define geometry.For Lines:ID Coordinates(0,1), (3,4), (5,6)(3,1), (5,2), (4,3)12
6 Spaghetti Vector Data Model Each point, line, or polygon is stored as a record in a file that consists of that entity’s ID and a list of coordinates that define geometry.For Polygons:ID Coordinates(2,4), (4,3), (3,6) , (2,4),(3,1), (5,2), (4,3), (3,2), (3,1)12
7 Spaghetti Vector Data Model Advantagessimpleefficient for display and plottingDisadvantagesinefficient for most types of spatial analysis
8 Vector Topologic Data Model Composed of points, lines, and polygonsNode: a point at the intersection of three or more linesIn addition to coordinate locations, the topologic relationships among geometric features are explicitly recorded
9 Vector Topologic Data Model BCa1a2a3a4n1n2Arc StartXY IntermediateXY EndXYa1 4,5 (4,8), (8,8), (8,1), (4,1) 4,3a2 4,5 (6,7), (6,3) 4,3a3 4,5 (1,3) 4,3a4 4,3 4,5Arc Coordinate DataArc Start End Left Righta1 n n Aa2 n n2 A Ba3 n n2 Ca4 n n1 C BArc TopologyNode Arcsn1 a4, a2, a1, a3n2 a2, a4, a3, a1Node TopologyID ArcsA a1, a2B a2, a4C a3, a4Polygon Topology
10 Vector Topologic Data Model Planar Enforcement:No two individual features can overlap.There are no ‘holes’ or ‘íslands’ that are not themselves features.Every feature is represented as a record in the attribute table.
11 Vector Topologic vs. Spaghetti Spaghetti: can encode as 2 or 3 polygons (and have 2 or 3 records in the attribute table)Topologic: must be encoded as 3 polygons (and have 3 records in the attribute table)
14 Hybrid vs. Integrated Approaches Hybrid Approach: stores spatial data and attribute data in different data models (typically relational data model for attribute data and proprietary data structure for spatial data).Integrated Approach: stores spatial and attribute data using the same data model (typically using the relational data model in a single RDBMS).
15 ESRI Shapefile Designed by ESRI for ArcView Implementation of the spaghetti vector modelAn individual layer stores a single type of geometry (i.e. point, line, polygon)No topology (but it can be calculated on the fly...)Draws relatively fast‘Open’ file format
16 ESRI ShapefileThree primary files in a shapefile: .shp, .shx, and .dbfAll files must share the same prefix for one shapefile,e.g. road.shp, road.shx, and road.dbf.shp : stores the feature geometry (binary).shx : index for .shp file.dbf : attribute data stored in dBASE format
18 ESRI Coverage Designed by ESRI for ArcInfo Implementation of the vector topologic data model‘Closed’ file formatEach coverage is a directory, with numerous files that store feature geometry, projection, registration, etc.Attribute data is stored in a separate INFO directory, which stores all attribute data for all coverages in its parent directory.
19 ESRI Geodatabase Designed by ESRI for ArcGIS Integrated approach implementing spaghetti vector data model in a relational DBMS (for vector)RDBMS is powered by Microsoft Jet (Access) or other DBMSTopology is generated on the flySupports versioning, multi-user edits, client-server architecture, other mainstream database functionality