Introduction to the Geodatabase. What is a Geodatabase? What are feature classes and feature...
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Transcript of Introduction to the Geodatabase. What is a Geodatabase? What are feature classes and feature...
• What is a Geodatabase?• What are feature classes and feature datasets?• What are domains• Design a personal Geodatabase• Import data to a Geodatabase
What is a Geodatabase?
• A container for tables, feature classes, feature datasets….• Tables – attributes of rows and columns• Standalone feature classes (conceptually like shape files)• Feature datasets (a collection of feature classes)• Rules and relationships
A relational database that contain geographic information
• Store geographic features represented as points, lines, or polygons, and their attributes;
• Can also store annotation and dimensions.
• Tables may contain additional attributes for a feature class
Feature classes…..
• Feature classes can be organized in Feature datasets.
• All feature classes in a feature dataset share the same coordinate system.
• Feature classes in a feature dataset can be organized into a geometric network. The network maintains topological relationships between its feature classes.
Feature datasets…..
Personal geodatabase - stores data in a Microsoft Access database
- size limit 2 GB- directly read through ArcCatalog- does not support raster data
Multiuser geodatabases - data stored in IBM DB2, Informix,
Oracle, or Microsoft SQL Server- connected through ArcSDE or direct- ArcSDE license necessary for editing- supports raster data
Personal vs. Multiuser Geodatabase
• All data (vector, raster, address, measures, CAD, etc.) is stored together in a commercial off-the-shelf DBMS
• Simplify support and maintenance, and reduce costs
• Allows multi-user access (with ArcSDE license)
• Support for intelligent features, rules, and relationships between feature classes
Why Geodatabase?
• Dynamic Geocoding
• Annotation subclasses
• Subtypes within Feature classes
• Coded attribute and range domains
• Improved topology and editing
More advantages…..
…however they are simply modern equivalents of shapefiles and coverages stored in a commercial database.
Confused?
-The geodatabase may seem complicated…..
- Geodatabases can be created and managed easily using the standard tools in ArcCatalog
- ArcMap and ArcToolbox provides tools to work with geodatabases
Geodatabases in ArcGIS
• Design process • Create an empty Geodatabase in ArcCatalog• Define the database structure• Set spatial reference and coordinate domains• Load data • Define topology rules and relationships
Creating a GeodatabaseThink before you create
Design process
• What data layers to include in the geodatabaseShape files – CoveragesLook-up tables
• How to organize the feature classes into logical feature datasets
• Think about what topolygy rules you may want to apply – how are the feature classes related to each other spatially?
• Shape files and coverages are converted to feature classes
• Attributes can be left out or renamed
• CAD data, dBase files, annotation etc. can be imported
• Data of the same spatial extent can be imported to the same feature dataset
Migrating existing data into the Geodatabase
Importing existing data
• In ArcCatalog or ArcToolbox• Tools and wizards are available• Works with coverages, shapefiles, tables, CAD etc.
Creating Feature Datasets• Right-click on the geodatabase – New – Feature Dataset
• Name the Feature Dataset and define the coordinate system
• Set X/Y domain
• Set Z domain and M domain
• Set manually or import from existing data sets
Coordinate Domains
Lost data
Large areaSmaller precision (1,000)
Small area larger precision (100,000)
(0,0)
Y
X
Max X and Y is 2.14 billion
Coordinate Domains
• The coordinate domain defines the area you can make edits in
• X and Y max is 2.14 billion for the database
• Default domain is 21000, 21000
• Define your coordinate domains correctly the first time – they cannot be changed
• You can have a different coordinate domain for each feature class
Setting X/Y Domain Precision
Min X ~ 2,145,320Max X ~ 2,657,580Min Y ~ 1,632,610Max Y ~ 1,967,940
1 ft units, 1/1000 ft accuracyPrecision = 1000/1 = 1000 (good enough)
1000
(0,0)
Y
X
Max X and Y is 2.14 billion
Most of the data is here in the database Large expansion options to the north and east
Coordinate Domains
Coordinate Domains CalculationsMin X ~ 2,145,320Max X ~ 2,657,580Min Y ~ 1,632,610Max Y ~ 1,967,940Precision 1000
These coordinates would put the data in the lower left corner – however we want to shift this to be able to expand in all directions
(MinX + MaxX)/2 – (2.14 x 109) / (1000 x 2) = X min 2,401,450 – 1,070,000 = 1,331,450 (MinY + MaxY)/2 – (2.14 x 109) / (1000 x 2) = Y min 1,800,275 – 1,070,000 = 730,275
(MinX + MaxX)/2 + (2.14 x 109) / (1000 x 2) = X max 2,401,450 + 1,070,000 = 3,471,450 (MinY + MaxY)/2 + (2.14 x 109) / (1000 x 2) = Y max 1,800,275 + 1,070,000 = 2,870,275
Min X ~ 2,145,320Max X ~ 2,657,580Min Y ~ 1,632,610Max Y ~ 1,967,940Precision 1000
Min X = 1,331,450 Max X = 3,471,450 Min Y = 730,275Max Y = 2,870,275Precision 1000
Default x/y domain Shifted x/y domain
Coordinate Domains Calculations
(0,0)
Y
X
Max X and Y is 2.14 billion
Most of the data is here in the database Large expansion options in all directions
Coordinate Domains
Why create Feature Datsets?
• Data organization• Topology rules• Shared boundaries• Geometric networks
Subtypes in feature classesSubtypes can only be created in ArcEditor and ArcInfo
- A subtype is a group of objects that have similar properties within the Geodatabase
For example the attribute ‘ZoneCode’ may have subtypes:- Commercial, Residential, Industrial
Landcover vegetation types may have subtypes:- Forest, Agriculture, Rangeland, Urban
Attribute Domains
• Attribute domains are properties of the Geodatabase - Multiple objects may use the same domain - Can be created using the Domains properties dialog box
• Defines legal values for field attributes - Range domains (allowable numeric value range) - Coded value domain (in dropdown menus)