References: Longley et al., 2nd edition, chapter 10; Creating,
Editing, and Managing Geodatabases for ArcGIS 9, ESRI Virtual
Campus
Buffer
Lecture 9: Geographic Databases (ArcGIS environment)
Yehuda Bock
SIO 110
February 4, 2009
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Geographic Database Systems: Features, Advantages, Disadvantages, Components - Prof. Yehud, Study notes of Geology
An overview of geographic database systems, discussing their features, advantages, disadvantages, and components. A geographic database is a relational database that stores geographic data, offering capabilities such as data modeling and loading, indexing, query/manipulation language support, and storage management for large volumes of geographic records. The document also covers the basic building blocks of a geodatabase, including feature classes, feature datasets, nonspatial tables, topology objects, geometric networks, and relationship classes.
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References: Longley et al., 2nd edition, chapter 10; Creating,Editing, and Managing Geodatabases for ArcGIS 9, ESRI VirtualCampus
Buffer
Lecture 9: Geographic Databases (ArcGIS environment)
Yehuda Bock
SIO 110
February 4, 2009
What is a database?
“A database is an integrated set of data on a particular subject.” DBMS: “A database management system is a softwareapplication designed to organize the efficient and effectivestorage and access of data.” RDBMS: “A relational DBMS comprises a set of tables, each a2-D array of records containing attributes about the objects understudy”
Object (feature) classes – an organized collection of data on a particular subject (theme)
Object classes are stored in database tables
Table rows contain objects
Table columns contain object attributes (properties)
Basic Rules:
Only one value is in each cell at the intersection of arow and column
All values in a column are about the same subject
Each row is unique (no duplicate records)
No significance to the sequence of rows or columns
Database tables can be joined together
Database tables
Cardinality
Relationship between features in two tables
Symbolizing
One-to-one
Many-to-one
ManyMany
toto
manymany
One-to-many
Joins
Relates
Origin table Primary key
Destination table Foreign key
Relationship Classes
SQL is the standard database query language
Command line interface
Compiled in programming language (C/C++, Java,Visual Basic)
Imbedded in graphical user interface (GUI)
Types of SQL Statements
Data definition language (DDL) statements create,alter, and delete relational database structures
Data manipulation language (DML) statementsretrieve and manipulate data
Data control language (DCL) statements handleauthorization access
SQL (Structured/Standard Query Language
What is a geodatabase?
A geodatabase is a relational database that stores geographic data. At its most basic level, the geodatabase is a container for storingspatial and attribute data and the relationships that exist amongthem. In a geodatabase, which is a vector data format, featuresand their associated attributes can be structured to work togetheras an integrated system using rules, relationships, and topologicalassociations.
Capabilities, cont.
Transaction services to hand short to long (typical of geographic) transactions
Security
Controlled update
Backup and recovery
DBA tools (setting up schema, creating indexes, maintenance)
Applications (designing database, user interfaces)
Application programming interfaces (API’s)
Geodatabase Components
The basic building blocks of ageodatabase are feature (object)classes, feature datasets, andnonspatial tables. Using these, youcan build more complex objects inyour geodatabase. You can createassociations among geodatabasecomponents based on spatialrelationships (topology) or attributes(relationship classes). If you want tomodel the flow of resources, such aswater or electricity, you can build ageometric network. Additionally,you can manage raster data using ageodatabase.
In addition to feature classes, feature datasets, andtables, a geodatabase can contain topology objects,geometric networks, and relationship classes. Rasterdata is stored outside the personal geodatabase.
Feature Classes
- A feature class is a collection ofgeographic features with the samegeometry type, attributes, and spatialreference. Feature classes can alsostore annotation (text or graphicsthat can be individually selected,positioned, and modified). • Feature classes may existindependently in a geodatabase asstandalone feature classes or theycan be grouped into feature datasets.
The South America geodatabase contains three standalone featureclasses: a point feature class of cities, a polygon feature class ofcountries, and an annotation feature class of country names.
Feature Datasets
- A feature dataset contains a group offeature classes that share the samespatial reference. That is, the featureclasses must have the same coordinatesystem and their features must fallwithin a common geographic extent. • Feature datasets are primarily used tostore feature classes that havetopological relationships, such asconnectivity, adjacency, or containment.For example, streams in a particularwatershed are connected to rivers;therefore, streams and rivers aretopologically related. • In order for a geodatabase to maintaintopological relationships among featureclasses, the feature classes must reside inthe same feature dataset.
The five feature classes in the Watershedfeature dataset have topologicalrelationships that should be maintainedwhen any of the feature classes are edited.
Topology
A geodatabase topology is aset of rules and properties thatdefines the spatialrelationships you want tomodel and preserve in yourdata. All feature classesparticipating in a geodatabasetopology must be in the samefeature dataset.
A geodatabase topology rule applies to a particulartype of spatial relationship. For example, Must NotHave Gaps is a rule that defines a spatial relationshipbetween polygon boundaries.
Geometric Networks
In a geodatabase, you can model real-world networks (e.g., streams joiningtogether to form larger streams, pipescarrying water to homes andbusinesses throughout a city, andpower lines carrying electricity) with ageometric network. Created from pointand line feature classes groupedtogether in a feature dataset, geometricnetworks enable you to define andanalyze the flow of resources toanswer questions such as: • Which streams will be affected by aproposed dam? • Which areas will be affected by awater main repair? • What is the quickest route betweentwo points in the network?
A water transmission network is modeled in thegeodatabase using a geometric network.