copyright © 2005 bruce kessler all rights reserved ch. 2 geodatabase basics laying the foundations
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Copyright © 2005 Bruce Kessler All Rights Reserved
Ch. 2GeoDatabase Basics
Laying the foundations
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-2
Goals
HistoryBenefits / disadvantagesFeature geometryTypes of GeoDatabasesManaging a GeoDatabase
– Structure– Spatial reference
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-3
GeoDatabase History/Description/AdvantagesMost of the structure was developed before ArcGIS
Desktop softwareThe framework for vector, raster, and tabular data
storage in ArcGISUnique data formatMethod for storing spatial and attribute data as well as
other types of data (raster, tables, relationships, etc.)Has integrity rulesHas operatorsMethod for supporting transactional views: versionsA means for modifying object behavior
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-4
Before Using A GeoDatabase
Buy a full set of manuals!!!!Research your topics using White PapersKnow how to and use the on-line help
resources from ESRI – especially the Forums
A
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-5
Benefits of a GeoDatabase
Centralized managementLarge data management in a continuous
integrated environment: raster/vector/tabular/CAD (SDE)
Multi-user editing (SDE)
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-6
Benefits of a GeoDatabase
Topology– Complex geometric networks – Geometric relationships within and between multiple
feature classes
Maintained through rules – simple polygon example
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-7
Benefits of a GeoDatabase
Create and edit topologically integrated features with automatic maintenance
Easily control exceptions to ruleSupport of advanced data types:
measures, functional curves, Z valuesFeature-linked annotation
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-8
Benefits of a Geodatabase
Efficient data entry with rules, relationships, and behavior
Schema can be developed with CASE tools
Custom objects
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Review of Feature Geometry
PointMulti-pointLine
– User-shaped– Curves– Single / multi-part
Polygon– Single / multi-part
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-10
Review of Feature Coordinates
X, Y – this is easyZ
Elevation
M
Measure
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Two types of GeoDatabases
Personal– Access
Multi-user– SDE
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-12
GeoDatabase (GDB) structure
Stores– Feature datasets– Feature classes– Tables– Raster– More
A unique structure within the GDB
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GDB Objects: Feature Class (FC)
A collection of features– Each feature class has one geometry type (point,
multi-point, line, polygon)Can be stored in a feature dataset or ‘stand-alone’Attributes are
stored with coordinate data in one table
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-14
Spatial Reference
Property of a feature class or feature datasetComponents
– Coordinate system– Coordinate domain
Permanent after definition is saved– Warning: it may look like you changed the
coordinate system, but you can’t and don’t try. It messes things up!
See next slide for more information
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-15
Spatial Reference
A
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-16
Coordinate domainExtent of available coordinates
– Min and max X,Y coordinates– Precision = storage units per
map unitExample, 1000 mm per meter
Make sure it covers study area– Allow for growth
ArcCatalog default– Import: data plus room for growth
Set your own– Import from existing data– Type in extent for study area
2.14 billion storage units
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-17
Accuracy and PrecisionAccuracy in the Data
– Scale of source map scale will determine accuracy*1:600 (1”=50’) ± 1.7 feet1:1,200 (1”=100’) ± 3.33 feet1:2,400 (1”=200’) ± 6.67 feet 1:4,800 (1”=400’) ± 13.33 feet 1:24,000 ± 40.00 feet
– PrecisionAbility to store the accuracy
– Significant digits• Single precision 6-7 precise digits• Double precision 13-14 precise digits• Geodatabase 0-10 precise digits
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-18
Domain
A property of a feature dataset or feature class (cannot change once set)
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-19
Standard FieldsFeature classes have default fields
– ObjectID – unique identifier– Shape – contains coordinates of feature– Area – automatically calculated and maintained for polygons
Shape_Area (Personal GDB)
– Length – automatically calculated and maintained for lines and polygons
Shape_Length (Personal GDB)
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-20
GDB Objects: Feature Dataset
A collection of feature classes– Environment for spatial reference– Environment for topology – Environment for coincident geometry and linked
annotation– Feature classes inherit spatial reference
Data loaded are projected on the fly, if necessary
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-21
Managing Your GDB
ArcCatalog is your main tool to manage the schema– Construction of component parts– Organization of those parts– Properties for the parts
Many capabilities are available– Some are not on the default GUI
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-22
Creating a GDB
Personal– Use ArcCatalog
Multi-user– Must be done at the
system level A
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Creating an empty feature class
Two locations available: stand-alone and within a feature dataset
A
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Creating a feature dataset
A
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-25
Tips
Projecting data– Must create a new feature class
PGDB is 2 GB maxRead-only on a PGDB will restrict some
analyses, such as Select by LocationUse compact to clean up temporary filesAll table names need to be unique
Copyright © 2005 Bruce Kessler All Rights Reserved Skills for the GeoDatabase 2-26
Ex 2
Create a Personal GDBCreate an empty Feature ClassCreate a Feature DatasetCreate a Feature Class within the
Feature Dataset