Transcript database

Introduction to the
Geodatabase
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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 relational database that contain
geographic information
• 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
Feature classes…..
• 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 datasets…..
• 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.
Personal vs. Multiuser Geodatabase
Personal geodatabase
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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
Why Geodatabase?
• All data (vector, raster, address, measures, CAD,
etc.) is stored together in a commercial off-theshelf 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
More advantages…..
• Dynamic Geocoding
• Annotation subclasses
• Subtypes within Feature classes
• Coded attribute and range domains
• Improved topology and editing
Confused?
-The geodatabase may
seem complicated…..
…however they are simply
modern equivalents of
shapefiles and coverages
stored in a commercial
database.
Geodatabases in ArcGIS
- Geodatabases can be created and
managed easily using the standard
tools in ArcCatalog
- ArcMap and ArcToolbox provides
tools to work with geodatabases
Creating a Geodatabase
Think before you create
• 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
Design process
• What data layers to include in the geodatabase
Shape files – Coverages
Look-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?
Create a new Geodatabase
in ArcCatalog
Migrating existing data into
the Geodatabase
• 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
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
Max X and Y is 2.14 billion
Lost data
Y
Large area
Smaller precision (1,000)
Small area larger precision (100,000)
(0,0)
X
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
What is max/min X and Y on the map?
Max X and Y
Min X and Y
Setting X/Y Domain Precision
1000
Min X
Max X
Min Y
Max Y
~ 2,145,320
~ 2,657,580
~ 1,632,610
~ 1,967,940
1 ft units, 1/1000 ft accuracy
Precision = 1000/1 = 1000 (good enough)
Coordinate Domains
Max X and Y is 2.14 billion
Y
Most of the data is here in the database
Large expansion options to the north and east
(0,0)
X
Coordinate Domains Calculations
Min X ~ 2,145,320
Max X ~ 2,657,580
Min Y ~ 1,632,610
Max Y ~ 1,967,940
Precision 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
Coordinate Domains Calculations
(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
Default x/y domain
Min X ~ 2,145,320
Max X ~ 2,657,580
Min Y ~ 1,632,610
Max Y ~ 1,967,940
Precision 1000
Shifted x/y domain
Min X = 1,331,450
Max X = 3,471,450
Min Y = 730,275
Max Y = 2,870,275
Precision 1000
Coordinate Domains
Max X and Y is 2.14 billion
Y
(0,0)
Most of the data is here in the database
Large expansion options in all directions
X
The shifted x/y domain allows for
editing within this window
Max X, Max Y
Min X, Min Y
Why create Feature Datsets?
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Data organization
Topology rules
Shared boundaries
Geometric networks
Subtypes in feature classes
Subtypes 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)
Questions?