Spatial Concepts: Data Models 2 2009/2010 CGI GIRS
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Data modeling in 4 steps 1. Geographical perception Continuous phenomenon Discrete phenomena Virtual boundaries Tangible boundaries altitude, EM radiation entities, units, objects municipality border fence nature reserve 2. Geographical description Geo Field Geo Object sampling boundaries, delineation 3. Data structure Raster based Vector based 4. Data sets relational Geometry (vector en raster) Thematic attributes 3/31
From real world to GIS Real World Geo data modelling Database & application by files and programmes Data structure geometric/thematic by a data model Spatial perception Spatial description by an information model 4/31
Example 1: CBS (Dutch Census Office) borders of residential areas, town districts and municipalities spatial perception spatial description geometric structure discrete and virtual phenomena object based vector structure (polygon features) 5/31
Example 2: LGN (Dutch Land Use Inventory) land use types spatial perception spatial description geometric structure discrete and tangible phenomena location based raster structure (raster cells) 6/31
Geometry Position and orientation 1. Coordinate system 2. Units (Kilometers) 3. Coordinates (X= 183.4990, Y=422.8125) Shape and size Rectangular, triangular Size: 200 m² Topology Inside, borders, ends, crosses 7/31
Vector structures Vector structure for point, lines and polygons Topology is a key aspect in the structure 8/31
Topology The description of how spatial features are related to each other. Conceptual (description) Geometrical data structure 9/31
Topology 2 Topologic relations in an object object based based description. Discussion of examples Area Area relation Neighbors Island Touches Line Line branches crosses Line Area inside ends on ends in crosses borders 10/31
Topology 3 relative location of spatial objects invariant for coordinate transformation Examples 1. object 3 is located on a line between objects 1 and 19 2. object 7 crosses object 9, 11 and 14 3. object 9 is located inside object 11 11/31
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Topology implemented by ESRI Coverage (predefined topology ArcInfo) (1981) Shapefile (no topology Arcview) (1993) Geo database (you define topology ArcGIS) (2001) 13/31
Example shapefile 14/31
Geodatabase topology rules 15/31
Raster structure 16/31
Raster datamodel Integer raster Nominal, Ordinal ( Categorical), Interval (Numerical) value attribute table Floating point raster Numerical (mainly Ratio) no value attribute table (too many records) 1 1 2 2 3 2 2 2 3 3 2 2 Value attribute list Value Description 1 Forest 2 Town 3 Meadow 17/31
Structures for attributes Tables Type of thematic attribute data (nominal, ordinal, interval and ratio) Relational model (normalization) Relation types: One to one, etc 18/31
Relational data model A collection of tables, which can be related to each other by attributes whose values can uniquely identify a record in a table. 19/31
Related data sets 1 Arable A A Private ownership 2 Non-arable B B State ownership 3 Forest A C Protected area 6 Forest C OTHER THEMATIC ATTRIBUTES 7 8 Forest Forest B A OTHER ENTITIES/OBJECTS 1 5,005 price index 1 1 1,003 3,000 tax index yield index MORE THEMATIC ATTRIBUTES 20/31
Related data sets (join) 1 Arable A A Private ownership 2 Non-arable B B State ownership 3 Forest A C Protected area JOIN 1: 1 / M: 1 21/31
Related data sets (linkage) JOIN ( 1: 1 AND M : 1 ) 1 Arable A A Private ownership RELATE 2 Non-arable B B State ownership (1:N) 3 Forest A C Protected area 1 1 1 5,005 1,003 3,000 price index tax index yield index 22/31
Related data sets (merge) JOIN RELATE 1 5,005 1 1,003 1 3,000 1 Arable 2 Non-arable 3 Forest 6 Forest 7 Forest 8 Forest price index tax index yield index A B A C B A A Private ownership B State ownership C Protected area MERGE! ADD 23/31
Study area : thematic data Ecologic research 24/31
Study area field work 25/31
Measurement scales Nominal grass, forest Ordinal good, well, bad / yes, no Interval noise in Decibel, temp degr. C Ratio speed in m/s, temp in degr. K Difference Order Distance Ratio 26/31
Measurement scales 2 Qualitative rank unit zero point Nominal Ordinal Quantitative Interval Ratio 27/31
Measurement scales example Table Provinces name size av. Income Euro 1 Utrecht small 30.000 2 Gelderland big 28.000 28/31
Study area data set 29/31
Summary spatial perception continuous and discrete phenomena ( geometrically and thematically defined) tangible and virtual features topology spatial description object based (delineated) and field based (sampled) descriptions geometric structure vector and raster structure features with and without topology database thematic measurement scales and geometric description in relational tables join, link and relate 30/31
Study material Theory Chang, 2006, 2008 Chapter 3.1, 3.2, 3.3, 3.4; Chapter 5.1, 5.3; Chapter 9 Practical: Exercise Module 1 Wageningen UR
Topology included in data structure (Coverage) Topology based vector data model (coverage in ArcGIS) Storage spatial and attribute data separately in (related) tables 3 basic topological relations: connectivity (arcs connect each other at nodes) area definition (an arc is defined by a series of connected arcs) contiguity (arcs have directions and left and right polygons) Note predefined topology! 32/31
No Topology included in data structure non topological vector datamodel (Shape in ArcGIS) storage spatial and attribute data separately in (related) tables point: X, Y coordinates; line: point series; polygon: line series NO files to describe spatial relationships between geometric objects advantage: display + interoperable (less software dependent) 33/31