Geodatabase Kyung Hee University Geography Jinmu Choi 1

2 Basic Concepts in a Geodatabase Topics What is a geodatabase (3) Geodatabase Types (2) GDB Physical Structure (5) Complex Objects in GDB (5) Raster in GDB (4) GDB Design (6) Summary and Next…

3 GeoDB vs. DB Spatial component Vector: discrete objects Raster: continuous phenomena TIN: surfaces Locators and address: references to places A framework for coordinate system Topologically integrated sets of features Networks and subdivisions Relationships btw. objects and features Natural behavior with rules

4 What is a geodatabase A relational database that stores geographic data Spatial and attribute data Relationships between them Rules and topological associations

5 Advantage of Geodatabase More accurate representation of the real world Built-in functions Centralized GIS data management Continuous sets of features Advanced feature geometry Flexible, rule-based topology More accurate data editing Feature-linked annotation Custom features Geometric networks UML & CASEtool support XML data exchange Versioning

6 Types of Geodatabase Personal GDB MS Access database with MS Jet engine File geodatabase or SQL server express All functionality except versioning Storage: 2 G, 4G, Unlimited Multiuser GDB Workgroup or enterprise geodatabase ArcGIS-ArcSDE-Relational DB Oracle, SQL server, Informix, DB2, Sybass Many user to view and edit the same data Multiuser working ENV: long transaction and versioning

7 Personal vs. Multiuser GDB DBMS Client/Server Long Transactions Disconnected Editing Editors Raster Data Size IBM DB2, Informix, Microsoft SQL server, Oracle Yes 1 or more at the same time Stored Unlimited Multiuser Microsoft Access SQL server express File structure No 1 at a time Referenced Up to 2GB, 4GB, Unlimited Personal

8 Physical Structure of GDB Geodatabase Feature datasets Object classes, subtypes Features classes, subtypes Relationship classes Geometric networks Planar topologies Domains Validation rules Raster datasets Rasters TIN datasets nodes, edges, faces Locators Addresses, X.Y location ZIP Codes, Place names Spatial Reference

9 Basic Geodatabase Structure Three primary components Feature classes A collection of features that share the same geometry type and spatial reference Feature datasets A collection of feature classes Must have the same spatial ref. Objects Nonspatial attribute tables that can be associated with feature classes

10 Feature Classes A collection of geographic features The same geometry type, attributes, and spatial reference Ex: telephone poles in London Streets, Lon districts Standalone feature class Grouped into a dataset Ex. Point: Cities Polygon: Country Annotation: country name

11 Feature Datasets A group of feature classes Feature classes have the same coordinate system Features must fall within a common geographic extent Primarily to store feature classes that have topological relationships Ex. Streams in a particular watershed To maintain topological relationship between classes, they should be in the same datasets

12 Nonspatial Tables Two types of tables Feature class tables and nonspatial tables (Objects) Tables are managed in ArcCatalog and edited in ArcMap Traditional row-column format Feature class tables have geometry column Nonspatial tables are standalone and can be related to feature class tables

13 More Complex Objects Building more complex objects in a geodatabase Topology To create spatial associations among GDB components Geometric networks To model flow of resources, such as water or electricity Relationship classes To model relationship among features and objects in GDB Raster catalog or dataset Personal geodatabase: Link by path with outside raster data Multiuser geodatabase: Stored inside database with own raster format

14 Topology Topology defines spatial relationships among features Creating topology is related to your analysis For modeling a watershed network, all features must be connected Otherwise, the result of any analysis will be flawed Three types of topology Geodatabase topology Map topology Topology for geometric network

15 Topology Types Geodatabase topology A set of rules and properties for spatial relationships More than 20 built in rules All features classes with a geodatabase topology rules should be in the same feature dataset Map topology Temporary topological relationships among features only during editing session ArcMap topology editing tool Topology for geometric network Maintained automatically in a geometric network

16 Geometric Networks Network created from point and line feature classes grouped together in a feature dataset Streams joining together to form larger streams Pipes carrying water to homes and businesses throughout a city Power lines carrying electricity To define GN, analyze a flow Which streams will be affected by a proposed dam? Which areas will be affected by a water main repair? What is the quickest route between two points in the network?

17 Relationship classes To help a geodatabase more accurately reflect the real world and facilitate data maintenance Building are always located on parcels Changes on the ownership Under relationship, if a feature changes, related features are updated automatically Properties of the relationships To control related features Rules for valid relationships To control limitations

18 Raster Data Depends on whether a personal or a multiuser geodatabase In a personal geodatabase, raster data is referenced rather than physically stored In a multiuser geodatabase, raster data is physically stored just like vector data. With both personal and multiuser geodatabases, View and manage raster data much as vector data Two types of raster objects Raster dataset and Raster catalog

19 Raster Dataset A raster dataset created from one or more individual raster From multiple raster, the data is mosaicked, or aggregated, into a single, seamless raster dataset Areas of overlap removed The input raster must be contiguous (adjacent) Having the same properties, including the same coordinate system, cell size, and data format For each raster dataset, *.img (ERDAS IMAGINE file) created Raster dataset are always managed by the geodatabase. The.img files are stored in a separate folder with the same name as the geodatabase In ArcCatalog, if the geodatabase is moved to another location, the folder containing the.img files moves with it

20 Raster Catalogs A collection of raster Noncontiguous Stored in different formats Having other different properties To view all the raster in the catalog, they must have the same coordinate system and a common geographic extent A raster catalog is defined as a table in the geodatabase Each raster in the catalog is represented by a row in the table GDB does not manage raster in the catalog The locations of the raster are recorded in the raster catalog table, but if the geodatabase moved, the raster data not move with it

21 Raster Dataset vs. Catalog Raster DatasetRaster Catalog Single dataset built from one or more raster Collection of raster Homogeneous source data: same resolution, format, coordinate system Heterogeneous source data: different resolutions, formats, data types, file sizes Faster displaySlower display. The more raster, the slower the display Loss of overlapping pixels when mosaicked Overlapping pixels are preserved One metadata fileMetadata files for the catalog and for each raster

22 Geodatabase Design Geodatabase is an instance of a relational database The bridges between the real world features and digital objects in a relational database Data model captures the user’s view of data: Logical model Database model implements the logical data model: Physical model Within the framework of relational database

23 Logical Data Model The set of objects of interest and to identify the relationships between them Validating data model against the organization’s practices and procedures Iterative modeling process to answer ‘Yes’ Does it represent all data without duplication? Does it support an organization’s business rules? Does it accommodate different views of data for distinct groups of users?

24 Physical Database Model To define the database schema and create new databases for data entry Classes in logical model may be splitted or joined when implemented in tables Logical model and database elements An object = an entity stored as a row Attributes = qualities of objects as a column Set of objects = A class as a table

25 Guidelines for Building GDB

26 UML Diagrams Classes and objects Abstract class No instance Specifications Creative class Create instances Instantiable class A property of another class Relationships Association btw. classes Multiplicity: 1, 0..1, M..N, * or 0..*, 1..* Type Inheritance Specialized classes To share properties and methods

27 Relationships in UML Instantiation One object’s method creates an object from another class Aggregation Asymmetric association A Whole and Parts Composition Stronger form of aggregation Whole controls lifetime of parts

28 Summary What is a geodatabase Advantages of a geodatabase Geodatabase types Basic geodatabase structure Methods for accessing geographic data Design geodatabase model Reading UML model

29 Next… Lab 1. Exploring the structure of a GDB Lecture Maps and layers Visualization with a geodatabase Read: Modeling Our World, Ch 2. Lab 2.