Building geodatabase • Building a geodatabase
Create a new geodatabase
• Designing the geodatabase •
(Think before your create)
• Creating a new geodatabase •
Defining GDB structure
(Name and location only)
• Defining the geodatabase structure •
(Schema and data)
• Entering spatial data •
Design geodatabase
(Loading or automation)
Geodatabase
Entering spatial data
• Define additional properties •
(Validation, relationships, networks)
Define additional properties
Geographic database design • The creation of conceptual, logical, &
physical models in the six practical steps:
10 steps designing geodatabases Identify the key thematic layers based on information requirements
3
Specify the scale range and spatial representation for each thematic layer
4
Group representation into datasets
5
Define the tabular database structure and behaviour for descriptive attributes
6
Define the spatial properties of datasets
7
Propose a geodatabase design
8
Implement, prototype, review, and refine design
9
Design work flows for building and maintaining each layer
10
Document design using appropriate methods
Conceptual design
2
Physical design
Identify the information products that will produced with GIS
Logical design
1
Geodatabase design steps • Start with thematic layers
Thematic layers of forest
Develop by the Industry Forestry Working Group
Creating a new geodatabase • Create a new
geodatabase using ArcCatalog • Create new • Rename default name
Three methods of creating geodatabases
Three methods of creating geodatabases • Create from scratch manually • Use tools in ArcCatalog to create schema • Importing existing data/database schema • Can convert by importing schema from existing datasets • Use CASE tools and UML to automate database creation. • Can use CASE tools to create new custom objects and/or generate a geodatabase schema from UML • CASE (Computer Aided Software Engineering) • UML (Unified Modeling Language)
Create data/database schema from scratch manually • Define structure using ArcCatalog • • • •
Feature datasets Feature classes Tables Relationship classes
• What to Define? • • • •
Database name Field name and properties Spatial reference Table relationship parameters
Importing existing data/database schema
• Import data and/or database schema • Shape files, coverage, features class & CAD • INFO, dBase tables
• Options while importing • Rename object • Rename or exclude attribute
columns • Modify spatial reference • Insert feature class into feature dataset
Importing forestry data model schema
Use CASE tools and UML to define database structure • Physical Design using UML • Feature class, relationship class, subtype and/or domain schema
• Design large database with visualization and documentation of data relationship and attributes
Entering Spatial Data • Spatial data automation options • Analog data: digitizing or scanning • ESRI formats: importing and loading • Other digital data: data conversion • Data Mapping • Vector geometry types • • •
X, Y: Points, multipoints, lines, polygons Z: Optional position in Z (e.g. elevation) M: Optional linear measurement (e.g. milepost)
• Field mapping • Spatial Reference
The Geodatabase data model • The geodatabase is a vector data format introduced by ESRI with ArcGIS® software.
What is a geodatabase? • Short for a geographic database • It is somewhat similar to the familiar file based coverage
and shapefile data models but it is different in some important ways • It provides support for advanced geometry • It supports user-defined relationships among feature classes • It provides efficient storage of raster data • Allows multi user editing • A geodatabase its today’s modern container for GIS data.
Why Geodatabase? • • • • • • • •
A uniform repository of geographic data Data entry and editing is more accurate Users work with more intuitive data objects Features have a richer context Better maps can be made Shapes of features are better defined Sets of features are continuous Many users can edit geographic data simultaneously
Geodatabase elements • • • • • • • • •
Objects & object classes Features & Feature classes Feature datasets Spatial references Domains Subtypes Relationships & Relationship classes Geometric networks Labels and Annotation
Objects & objects classes • • • • •
Geodatabases organize geographic data into a hierarchy of data objects. Objects are instances of an object class that have properties and behavior. Objects can be related to other objects via relationships Objects have unique system identifiers (OID) Object classes are tables in a geodatabase storing non-spatial data (e.g., Parcel owners)
• Objects in an object class have the same • •
Properties - stored in the table as attributes Behavior - implemented as a component
A row stores an Object
Object Classes (tables) Tree Table OID 175 …
Tree Type Eurycoma longifolia …………
Diameter (cm) 15
……. …….
…………
……. 77
Feature and feature class • Features are objects with required shape (Points, Multi-points,
Lines & Polygons) that represent a real world object in a layer on a map
• Features classes are collections of features with same type of feature geometry and attributes
• A feature class is also an object class which stores spatial objects (features) (e.g., Parcels)
• All the features in a feature class are in the same spatial reference • Feature classes which store topological features must be contained within a feature dataset to ensure a common spatial reference
Feature dataset • Containers for feature classes • Shared spatial reference • Analogous to a coverage • less restrictive • May also contain • relationship classes • geometric networks • Annotations
Spatial reference • Spatial Reference • Coordinate system • Spatial domain • Precision • Cautions • All feature classes within a
feature dataset share the same spatial reference. • Once created, the spatial domain for feature dataset/class cannot be changed. • Data outside extent of dataset need to be created in a new feature dataset or standalone feature class.
Coordinate system • Projection system & parameters • •
Geographic, UTM and State plane Datum, central Meridian, standard parallels, false northing and easting
• Define Coordinate system for feature dataset/classes •
Select: a predefined coordinate system
• • • •
Import: from existing geodatabase Create: a new coordinate system Modify: current coordinate system Save: for future use
Spatial domain • Spatial Domain • The allowable coordinate range for the geographic coordinates • X/Y Domain: • MinX, MaxX, MinY, MaxY • Z Domain: • Min, Max • M Domain: • Min, Max
Precision • The number of system units per one unit of measure (of distance). Precision determines the resolution of a map (geodatabase)
• For example: map unit is meter • Precision of 1: 1 system unit = 1 meter (resolution) • Precision of 1000: 1000 systems units = 1 meter
• 1 systems unit = 0.001 meter = 1 millimeter (resolution)
Subtype and Attribute Domain • Subtype • Attribute domain • Ranged domain • Coded value domain
• Associating domain with subtype • Attribute validation rules • Split and merge domain policies
Subtypes • Subset of features in a features class, or objects in a tables that share same attributes • It allowed: • Increase performance of geodatabase • Set a default value that will automatically apply when creating new features
• • • •
Apply coded or ranged domains Create connectivity rules Create topology Develop relationship rules
Domains • • • •
Attribute domains Describe the legal values of a field type Enforcing data integrity Constrain the values allowed for attribute tables or feature class
• Can be shared across feature classes, tables & subtypes
Domains
•
Why Subtypes and Attribute Domains Data Integrity • Prevent illegal attribute assignment to features, tables with out-ofrange data values
• For certain critical field, provide predefined codes as the only valid values
• Data Efficiency • Associate different subset of a feature class with different default values, attribute validation rules
• Allow efficient choice from a set of valid value descriptions rather than manually input the value itself
PowerPoles
Streets Primary
Secondary
Wood
Steel
ST, RD, AV, BLVD
Ln, Cir, Pl
20-30
30-50
Relationship and Relationship Class • Relationship •
•
Persistent and Dynamic association between objects in the geodatabase
•
Change to origin table can been seen when the destination access the relationship.
•
The relationship exist unless deleted. No merging of two tables
Common field with same data type
• • •
Between non-spatial objects (rows in tables) Between spatial objects (features in feature classes) Between spatial and non-spatial objects
• Relationship class •
A geodatabase relationship is stored in relationship classes. It is save as a record (row) in a relationship table.
Relationship
One parcel has one owner
One parcel has many owners
Many parcels have many owners
Geodatabase Relationship • Characteristics of relationship • • • •
Persisted relationship in the geodatabase Can enforce dependent behavior Can edit, query, and symbolized across relationship Can only relate tables within the same geodatabase
Origin
Destination
The architecture of a geodatabase
User data
System table
Inside a geodatabase
Key characteristics
ArcSDE GeoDB
File GeoDB
Personal GeoDB
Description
Various types of GIS datasets in relational database
Various types of GIS datasets in file system folder
Original data format i.e. Microsoft Access data files
Number of users
Multi-user (many readers many writers)
Single-user & small workgroups (many readers one writer)
Single-user & small workgroups (some readers one writer)
Storage format
Oracle, Microsoft SQL Server, IBM DB2, IBM Informix, PogstreSQL
Separate file folder on disk
Microsoft Access (.mdb)
Size limits
Up to DBMS limits
1 TB for each dataset
2 GB for each dataset. Performance decrease after 500MB
Platforms
Windows, UNIX, Linux
Cross-platform
Windows only
Database admin tools
Full DBMS functions
File system management
Windows file system management
Notes
Use ArcSDE technology
Can store data in read-only compressed format
Used as an attribute table manager
ArcSDE, file & personal geodatabase
Advantages of geodatabase • Large geodatabase feature classes can be stored seamlessly, not tiled • In addition to generic features, such as points, lines, and polygons, you can create custom features, such as transformers, pipes, and parcels
• These custom features can have special behavior to better represent real-
world objects. You can use this behavior to support sophisticated modeling of networks, data entry error prevention, custom rendering of features, and custom forms for inspecting or entering attributes of features
• Support’s multi-user editing • Supports topology. Topology in a geodatabase allows you to represent shared geometry between features within a feature class and between different feature classes
Why smart features? • Objects in the world have natural rules and relationship that they follow: • Rivers flow downstream • Road handle a level of traffic • Parcels have their own owners
The qualities of features • • • • • • • • •
Features have shapes Features have a spatial reference Feature have attributes Features have subtypes Features have relationships Features attributes can be constrained Features can be validated by rules Features can have topology Features can have complex behaviour
Features have shapes
• Type of geometry
• Points & multipoints • Polylines • Polygons
Features have a spatial reference • The shape stored in x & y values in a Cartesian coordinate system
Features have attributes • Fields in a feature class table • In relational database • Numeric, textual, or descriptive
Features have subtypes • Homogeneous sets of features but… • There may be variation among features • Increased control of other qualities of features • Attribute domains & roles Building
Features have relationships • All geographic objects have some relationship to other objects • Explicit relationships among geographic objects in different feature classes (house and parcel)
• Relationship to nonspatial objects (house and owner)
Features attributes can be constrained • Enhance security • Each attribute features can have attribute domain • Numeric range or list of values or default value
Features can be validated by rules • Objects in the world follow rules when they are placed or changed
• Use rules to: • constrain how the parts of a network are connected • the cardinality of relationships
Features can have topology • Many types of features have a precise relationship that is characterized as topology • E.g. • Parcels of land within a subdivision must adjoin each other exactly, without gaps or overlaps
• The lines and devices of a utility network must be continuously and unambiguously connected
Features can have complex behaviour
• More complex behaviors of features can be implemented by extending a standard feature and writing software code for a custom feature