WFM 6202: Remote Sensing and GIS in Water Management

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WFM 6202 Remote Sensing and GIS in Water
Management
Part-B Geographic Information System (GIS)
Lecture-4(b) Geo-Database

• Akm Saiful Islam

Institute of Water and Flood Management
(IWFM) Bangladesh University of Engineering and
Technology (BUET)
December, 2007
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Lecture Topic

• Understand basic Geodatabase concepts and
  structure
• Know the advantages in using the Geodatabase
  format
• Managing a GeoDatabase
• Creating GeoDatabase

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First Generation Storage/Linking

• Tabular/Spatial data is linked outside the
  database
• Links occur using unique IDs.Parcel Numbers
• Storage is still in separate locations

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Second Generation Storage/LinkingGeodatabases

• Tabular/Spatial data is stored/linked in a single
  location!!

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Benefits of a GeoDatabase

• Spatial attribute data integrity
• Intelligent Behavior
• Centralized Data Storage
• Increased Performance
• Advanced Analysis Capabilities
• Multi-user editing (SDE format)

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Benefits of Migrating to a GeodatabaseData
Integrity

• Maintain tabular data more efficiently
• Reduce typological data errors
• Maintain spatial data more efficiently
• Reduce spatial errors

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What is a Geodatabase?

• A spatial and attribute data container
• Relational database management system (RDBMS)
• Maintains data integrity
• Apply Rules and Behavior
• Native data format for ArcGIS

Relational Database - A method of structuring
data as collections of tables that are logically
associated to each other by shared attributes.
Any data element can be found in a relation by
knowing the name of the table, the attribute
(column) name, and the value of the primary key.
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2 Types of Geodatabase

• Personal Geodatabase
• Stand alone PC, MS Access database
• Supports individual and small groups on moderate
  size datasets
• Enterprise Geodatabase
• Exists on underlying RDBMS through Spatial
  Database Engine (SDE) e.g. SQL Server
• Usually runs on a dedicated server
• Supports many users and massive datasets
• Supports raster datasets

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Two types of GeoDatabases

• Personal
• Access
• Multi-user
• SDE

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The Personal GeodatabaseIts not Scary!

• Stores spatial and tabular data in an Access
  database format
• Sets the stage for future SDE geodatbase
  migration
• Edit in ArcView, ArcEditor or ArcInfo

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Geodatabase Features
Feature Dataset

• Contains tables, feature classes, feature
  datasets, topology rules, etc.

Topology
Feature Classes
Tables
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Geodatabase Elements
Geodatabase

• Feature data set

Geometric network
Feature class
Relationship class
Table
Annotation class
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GeoDatabase (GDB) structure

• Stores
• Feature datasets
• Feature classes
• Tables
• Raster
• More
• A unique structure within the GDB

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Feature Dataset

• Contains Feature Classes
• Must have same coordinate system
• Required for Topology
• Behavior relationships between feature classes.

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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

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Feature Class

• Stores a single feature type
• Point, Line, Polygon
• Can be standalone or member of a Feature dataset

Feature Dataset Feature Class
Stand Alone
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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

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Spatial Reference
A
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Coordinate domain

• Extent of available coordinates
• Min and max X,Y coordinates
• Precision storage units per map unit
• Example, 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
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Domain

• A property of a feature dataset or feature class
  (cannot change once set)

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Domains

• Spatial
• Attribute
• Range of values (e.g., 0-100)
• Coded values (e.g., 1 potatoes 2 wheat)

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The Spatial Domain

• The Geodatabase stores all geometry coordinates
  as positive integers
• Faster Display, Processing, and Analysis
• Better Compression (DBMS only)
• Efficient for managing topologic relationships
• Limited to 2,147,423,647 storage units.
• 2.14x109 meters, or miles, or inches, or ...

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Accuracy and Precision

• Accuracy in the Data
• Scale of source map scale will determine
  accuracy
• 1600 (150) 1.7 feet
• 11,200 (1100) 3.33 feet
• 12,400 (1200) 6.67 feet
• 14,800 (1400) 13.33 feet
• 124,000 40.00 feet
• Precision
• Ability to store the accuracy
• Significant digits
• Single precision 6-7 precise digits
• Double precision 13-14 precise digits
• Geodatabase 0-10 precise digits

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Example Spatial Domain

• All GIS Features Must Fit Within this Positive,
  32-bit Integer Space.

The Databases Spatial Domain
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Standard Fields

• Feature 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)

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Spatial Reference

• Property of a feature class or feature dataset
• Components
• Coordinate system
• Coordinate domain
• Permanent after definition is saved
• Warning it may look like you changed the
  coordinate system, but you cant and dont try.
  It messes things up!
• See next slide for more information

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Storing Feature Coordinates

• Two important considerations when storing
• feature coordinates in a Geodatabase
• All data is stored as positive, 32-bit integers
  (Spatial Domain)
• All data must maintain a Coordinate Precision.

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Coordinate Precision

• The geodatabase converts all coordinates into
  32-bit Storage Units.
• Storage Units are the smallest measurable unit
  that can be stored in a Geodatabase.
• Precision is used to convert coordinate system
  units into storage units.

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Example Coordinate Precision

• Precision is a Scale Factor
• Used to preserve decimal places before rounding
• Larger precision preserves more digits

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Example Precision Preservation
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Topology Objects

• Maintain data integrity
• Within feature class
• Between feature class
• Feature Dataset required
• Functionality
• Display Topology Errors
• Select and Correct Errors
• Validation

• Regarding map features, topology is relationship
  between features connectivity and adjacency.
• Geodatabase topology provides tools to ensure
  integrity of spatial data.

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Selected Topology Rules

• 25 available topology rules
• 2 Rules currently applied
• Must Not Overlap
• Must Not Have Gaps

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File Management

• Compacting the Personal Geodatabase
• Reduces file size
• Procedure
• In ArcCatalog, right click on the .mdb file
• Select the Compact Database option in the context
  menu

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Reference Data Locations

• Proscribed by the Standard for Geospatial Dataset
  File Naming
• http//dlnt20.fsa.usda.gov/scdm/DP/Parent3.htm
• Standard folder structure on shared f drive
• Geodata top level geospatial data folder
• Local Geodata Administrators have authority to
  create, delete, and change folders, but only as
  outlined in the standards document.

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Data Management File Naming Standards

• The current standard has 23 common geospatial
  dataset categories such as soils that consist of
  1 or more geospatial datasets.

ltdisk drivegt
geodata
plants
ltgeospatial dataset category (directory / folder)gt
soils
ltgeospatial dataset category (directory /
folder)gt
ltgeospatial datasetgt
soil_a_ks057


soil_p_ks057

ltgeospatial datasetgt
ltgeospatial datasetgt
soil_l_ks057

topographic_images
ltgeospatial dataset category (directory /
folder)gt
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Data Management File Naming Standards cont.

• Elements of a file name

Location Alpha or numeric FIPS code
soil_a_ks057
Feature category
Feature type a-polygon, l-line, p-point,
t-table, i-image, etc.

• A geospatial dataset file name should
• be less than 30 characters long
• consist of lower case a-z and numerals 0-9
• first character always a-z

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Data Storage and Backup

• Shared data in a service center must be on the f
  drive.
• Personal data can be stored on the c drive or h
  drive.
• c drive is not routinely backed up.
• h drive should contain important working files
  that can be routinely backed up.
• Local Geodata Administrators are responsible for
  ensuring backups are routinely being made of
  specific directories.
• Large, easily replaced datasets should not be
  routinely backed up because they can be obtained
  again.
• Files and directories that change regularly
  should be routinely backed up.

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GDB Design

• A critical step
• UML modeling for ArcGIS
• IBM Rational Rose
• MS Visio
• Class diagrams

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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

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Reading Schemas
Most data access technologies provide a way for
you to query the schema of a database, and obtain
information about the tables, stored procedures,
data types, users, and other content of a
database.
Logical
Structural
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Creating a GDB

• Personal
• Use ArcCatalog
• Multi-user
• Must be done at the system level

A
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Creating a new personal geodatabase

• Open ArcCatalog
• Choose a folder location
• Right click Choose New lt Personal Geodatabase

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Creating Feature Datasets
Right click your geodatabase Choose New lt
Feature Dataset
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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
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Creating Feature Datasets
Right click your geodatabase Choose New lt
Feature Dataset
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Feature Datasets Setting the
spatial reference

• Set the Projection
• Set the Domain
• Precision
• Extent

http//arcscripts.esri.com/ Search on Spatial
Domain
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Import existing data

• Navigate to the feature dataset or geodatabase
  icon in ArcCatalog
• Right Click
• Choose Import

Use this to import any existing format!
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Subtypes Domains

• Subtype
• Distinguish features within a single layer
• Maintain different domains within the same field
• Need ArcEditor or ArcInfo
• Domain
• Identify constrain attribute values
• Can utilize in ArcView

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Subtypes DomainsParcels
Example Subtype Boundary Line Domains
ROW Type
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Subtypes

• Must be long or short integer fields
• Created in ArcEditor or ArcInfo
• Increases the efficiency of the editing process
• Use when
• Standardizing a legend
• distinguishing different default values/domains
  within the same field

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Creating Subtypes

• In ArcCatalog
• Double click on a feature class
• Select the Subtype tab

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Creating Domains

• Created in
• ArcCatalog
• Double Click on the Personal Geodatabase Icon
• Choose the Domains tab

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Creating DomainsAssigning to Feature Classes

• In ArcCatalog
• Double click a feature class
• Choose the Fields tab
• Highlight a field
• Click Domain under the Field properties section

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Creating DomainsAssigning default values
Set in the Field Properties section
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Using Domains during the Editing Process
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Geodatabase TopologyPutting the power into your
hands

• Topology Rules
• Preset rules to define topological relationships
  to ensure connectivity, adjacency and coincidence
• Can be changed at any time
• Topology Tools
• Maintain spatial relationships
• Toolbar and Tasks

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Creating Topology

• Rules
• Land use boundaries overlap parcel boundaries
• Manholes overlap sanitary line endpoints
• Cluster Tolerance
• Min distance where vertices within tolerance are
  snapped
• Ranks
• Control what features move during validating
• Surveyed points will not move (snap) during the
  validation process

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Validating Topology

• Validate edited features using set topology rules
• Evaluate rules/tolerance and generates error
  notifications
• Snaps vertices using set cluster tolerance and
  ranks

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Create a New Topology

• Created in ArcCatalog
• Created within a Feature Dataset
• Topology Wizard
• Allows user to set Rules, Ranks, Tolerance, and
  perform initial Validation

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Final Topology
When added to ArcMap, will show errors from the
validation process
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Managing Topologies

• Right click on the Topology in ArcCatalog

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Topology ToolsMaintenance

• Standard toolbar in ArcView-ArcInfo
• Used in an editing environment in ArcMap
• Use in conjunction with Topology Tasks in Editor
  Toolbar

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Editor ToolbarMaintenance

• Topology Tasks
• Modify, Auto Complete Polygon and Reshape
• Allows user to use basic editing tools to alter
  vertices, replace lines, add adjacent polygons or
  alter existing polygons
• Use in conjunction with the Topology Edit Tool on
  the Topology Toolbar
• Remember
• Set snapping and snapping tolerance

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Flexible Editing

• Topology edit tool
• Allows for editing shared boundaries
• Builds a temporary topology cache within a given
  extent
• Faster performance
• Must use each time your extent changes
• Show shared features tool
• Move a boundary without effecting shared
  boundaries (temporary)
• Parcels land use
• Parcels and easements

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Validate Fix

• Validate after editing is complete
• Errors are highlighted
• Click the Fix Error button
• Select a feature and right click
• Fix
• Mark as an Exception
• Do Nothing

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Process in Review

• Plan for success
• Import data
• Set Subtypes Domains
• Create Topology
• Start editing!

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Tips

• Projecting data
• Must create a new feature class
• PGDB is 2 GB max
• Read-only on a PGDB will restrict some analyses,
  such as Select by Location
• Use compact to clean up temporary files
• All table names need to be unique

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Ex 2

• Create a Personal GDB
• Create an empty Feature Class
• Create a Feature Dataset
• Create a Feature Class within the Feature Dataset