1. Introduction to Geoinformatics L-2. Geographic Data Modeling
Dr. György SZABÓ associate professor
Budapest University of Technology and Economy
Department of Photogrammetry and Geoinformatics

2. Contents
OVERVIEW
Describes the process of data modeling and the various data models that have been used in GIS.
LEARNING OBJECTIVES
Define what geographic data models are and discuss their importance in GIS;
Understand how to undertake GIS data modeling;
Outline the main geographic models used in GIS today and their strengths and weaknesses;
Understand key topology concepts and why topology is useful for data
validation, analysis, and editing;
Read data model notation;
Describe how to model the world and create a useful geographic database.
Longley, Goodchild, Maguire, Rhind (2011) : Geographical Information Systems and Science
CH – 8. pp

3. The role of a data model in GIS

4. Levels of GIS data model abstraction

6. Different representational models of the same area in Colorado, USAB
aerial photograph
(B) vector objects, some digitized from the photograph

7. A photographic image used as a building object attribute in an electric facility system

8. Raster data of the Olympic Peninsula, Washington State, with associated value attribute table. Bands 4,3,2 from Landsat 5 satellite with land cover classification overlaid
(Screenshot courtesy ERDAS Inc.; data courtesy USGS)

9. Shaded digital elevation model of North America used for comparison of image compression techniques
Original image is 8,726 by 10,618 pixels, 8 bits per pixel. The inset shows part of the image at a zoom factor of 1,000 for the San Francisco Bay area

10. Representation of point, line, and polygon objects using the vector data model

11. A topologically structured polygon data layer
The polygons are made up of the polylines shown in the area polyline list. The lines are made up of the coordinates shown in the line coordinate list.
(Source: after ESRI 1997)

12. The contiguity of a topologically structured polygon data layer
For each polyline the left and right polygons are stored with the geometry data
(Source: after ESRI 1997)

13. An example of a georelational polygon dataset
Each of the polygons is linked to a row in an RDBMS table. The table has multiple attributes, one in each column.
(Source: after ESRI 1997)

14. An example of a street network

15. TIN surface of Death Valley, California
“wireframe” showing all triangles
(B) shaded by elevation
(C) draped with satellite image

16. The topology of a TIN
(Source: after Zeiler 1999)

17. Examples of applications that use the TIN data model
Landslide risk map for Pisa, Italy (Courtesy of Earth Science Department, University of Siena, Italy)
(B) Yangtse River, China
(Courtesy of Human Settlements Research
Center, Tsinghua University, China)

18. Example of split and merge rules for parcel objects
(B) merge
(Source: after MacDonald 1999)

19. Water distribution system water-facility object types and geographic relationships

20. Water distribution system network

21. A water-facility object model

22. An example of a CASE tool (Microsoft Visio) The UML model is for a utility water system

23. The modeling process The Modeling procedure:
Concept and procedures to translate real world observations into data that are meaningful in GIS
The Modeling procedure:
Phenomenon:
-          properties
-          connections
Entity:
-          type
-          attributes
-          relationship
Object:
-          geometry
-          quality
Symbol:
-          Graphic
-          Maps
-          Reports
-          Text
Physical reality
Real world model
Data model
Database
Presentation

24. Specification of the system data model
1. Object hierarchy, object catalog specification
-         Object groups- sub groups- objects
-         Object type, object name, object definition
2. Geometry, attributes, graphic specification

25. Entity hierarchy Object Super Class Object Sub Class-1
Hidrology
Boundary
Trafic
Vegetation
Object Super Class
Object Sub Class-1
Object Sub Class-n
Object Set
6000
7000
8000
9000
Aerial
Terestrial
Vater
7210
7220
7230
Highway
Mani road
7200
Secondary r.
Unpaved road
7240
Gov.
Municipal
Private
7221
7222
7223

26. Object properties Obj. Attributes Geometry vector raster Metr. Top.
Doc.
Fact

27. Object Catalog Table Object Name -Feature Class Object Hierarchy
Geometry
Legend
Attributes
Req. Geom. accuracy
Main_line
W_net L
ID, material, diameter, pressure, build_date, soil, …
Sec_line
ID, material, diameter, pressure, user_name
Fireplug P
ID, diamater1, diameter2, pressure
Parcel
User A
ID, parc_id, owner, adress, consumption
Block
ID, Block_name, unit_price
Public_area
Municipal
ID, Street_name
Error
Event
ID, Name, Err_type, date, Damage_cost

28. Vector Representation
Vector elements:
Ideal representation of precise, abstract phenomenas
Sharp idenfication of objects
Vector primitives:
Point
Line
Area

29. Coding vector data Numerical coding/ inner attributes
Thematic coding/ layers
Object oriented storage / complex objects

30. Raster representation
Raster model: ideal representation for area features
Pixel value – attribute
Pixel size – geometrical resolution
Pixel bite size – thematic resolution
Pixel position – geometrical accuracy

31. Raster attribute coding
Single layer – one attribute/cell Multi layer – several attributes 4/4

32. Conversion between Vector and Raster Models
R>V: ???
V>R: OK

33. Comparison of Vector and Raster models

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