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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 ... – PowerPoint PPT presentation

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Title: WFM 6202: Remote Sensing and GIS in Water Management


1
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, 2008
2
Lecture Topic
  • Understand basic Geodatabase concepts and
    structure
  • Know the advantages in using the Geodatabase
    format
  • Managing a GeoDatabase
  • Creating GeoDatabase

3
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

4
Second Generation Storage/Linking Geodatabases
  • Tabular/Spatial data is stored/linked in a single
    location!!

5
Benefits of a GeoDatabase
  • Spatial attribute data integrity
  • Intelligent Behavior
  • Centralized Data Storage
  • Increased Performance
  • Advanced Analysis Capabilities
  • Multi-user editing (SDE format)

6
Benefits of Migrating to a Geodatabase Data
Integrity
  • Maintain tabular data more efficiently
  • Reduce typological data errors
  • Maintain spatial data more efficiently
  • Reduce spatial errors

Pro-West Associates
7
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.
8
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

9
Two types of GeoDatabases
  • Personal
  • Access
  • Multi-user
  • SDE

10
The Personal Geodatabase Its 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

11
Geodatabase Features
Feature Dataset
  • Contains tables, feature classes, feature
    datasets, topology rules, etc.

Topology
Feature Classes
Tables
12
Geodatabase Elements
Geodatabase
  • Feature data set

Geometric network
Feature class
Relationship class
Table
Annotation class
13
GeoDatabase (GDB) structure
  • Stores
  • Feature datasets
  • Feature classes
  • Tables
  • Raster
  • More
  • A unique structure within the GDB

14
Feature Dataset
  • Contains Feature Classes
  • Must have same coordinate system
  • Required for Topology
  • Behavior relationships between feature classes.

15
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

16
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
17
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

18
Spatial Reference
A
19
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
20
Domain
  • A property of a feature dataset or feature class
    (cannot change once set)

21
Domains
  • Spatial
  • Attribute
  • Range of values (e.g., 0-100)
  • Coded values (e.g., 1 potatoes 2 wheat)

22
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 ...

23
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

24
Example Spatial Domain
  • All GIS Features Must Fit Within this Positive,
    32-bit Integer Space.

The Databases Spatial Domain
25
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)

26
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

27
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.

28
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.

29
Example Coordinate Precision
  • Precision is a Scale Factor
  • Used to preserve decimal places before rounding
  • Larger precision preserves more digits

30
Example Precision Preservation
Coordinate system units Precision Storage units
Meters 100 1 cm
Meters 1000 1 mm
Meters 50 2 cm
Feet 12 1 inch
31
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.

32
Selected Topology Rules
  • 25 available topology rules
  • 2 Rules currently applied
  • Must Not Overlap
  • Must Not Have Gaps

33
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

34
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.

35
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
36
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

37
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.

38
GDB Design
  • A critical step
  • UML modeling for ArcGIS
  • IBM Rational Rose
  • MS Visio
  • Class diagrams

39
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

40
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
41
Creating a GDB
  • Personal
  • Use ArcCatalog
  • Multi-user
  • Must be done at the system level

A
42
Creating a new personal geodatabase
  • Open ArcCatalog
  • Choose a folder location
  • Right click Choose New lt Personal Geodatabase

43
Creating Feature Datasets
Right click your geodatabase Choose New lt
Feature Dataset
44
Creating an empty feature class
  • Two locations available stand-alone and within a
    feature dataset

A
45
Creating a feature dataset
A
46
Creating Feature Datasets
Right click your geodatabase Choose New lt
Feature Dataset
47
Feature Datasets Setting the
spatial reference
  • Set the Projection
  • Set the Domain
  • Precision
  • Extent

http//arcscripts.esri.com/ Search on Spatial
Domain
48
Import existing data
  • Navigate to the feature dataset or geodatabase
    icon in ArcCatalog
  • Right Click
  • Choose Import

Use this to import any existing format!
49
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

50
Subtypes Domains Parcels
Example Subtype Boundary Line Domains
ROW Type
51
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

52
Creating Subtypes
  • In ArcCatalog
  • Double click on a feature class
  • Select the Subtype tab

53
Creating Domains
  • Created in
  • ArcCatalog
  • Double Click on the Personal Geodatabase Icon
  • Choose the Domains tab

54
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

55
Creating DomainsAssigning default values
Set in the Field Properties section
56
Using Domains during the Editing Process
57
Geodatabase Topology Putting 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

Pro-West Associates
58
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

Pro-West Associates
59
Validating Topology
  • Validate edited features using set topology rules
  • Evaluate rules/tolerance and generates error
    notifications
  • Snaps vertices using set cluster tolerance and
    ranks

Pro-West Associates
60
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

Pro-West Associates
61
Final Topology
When added to ArcMap, will show errors from the
validation process
62
Managing Topologies
  • Right click on the Topology in ArcCatalog

63
Topology Tools Maintenance
  • Standard toolbar in ArcView-ArcInfo
  • Used in an editing environment in ArcMap
  • Use in conjunction with Topology Tasks in Editor
    Toolbar

Pro-West Associates
64
Editor Toolbar Maintenance
  • 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

65
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

Pro-West Associates
66
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

67
Process in Review
  • Plan for success
  • Import data
  • Set Subtypes Domains
  • Create Topology
  • Start editing!

Pro-West Associates
68
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

69
Ex 2
  • Create a Personal GDB
  • Create an empty Feature Class
  • Create a Feature Dataset
  • Create a Feature Class within the Feature Dataset
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