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ArcGIS 9 and the Geodatabase
By Hal Reid
(Aug 18, 2004)


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arcgis_9-geodatabase_edited1 The concept of a geodatabase is to provide a set of best practices, for the creation of a data model that well addresses the need for storing geographic data and provide a set of rules that govern the post and extraction process.ArcGIS 9 and the way it works with the geodatabase have been improved to increase performance.

Why this is important is that as data set become larger and accessible by multiple users, without the proper practices, performance is reduced, the data loses standards and interoperability may be lost.

In ArcGIS 9 there were several overall goals for improvement.These were outlined by James Neild and Gudmundur Hafberg (ESRI), in their presentation at the ESRI Users' Conference.Those improvements are outlined here along with ESRI's ten steps in geodatabase design.

Goals

  • Make ArcSDE significantly faster - (faster queries, raster enhancements)
  • Reduce the server load
  • Reduce the network traffic
  • Reduce the number of SQL statements (an example was that in one application, they were able to reduce the number of SQL queries from around 4,000 to 279).
  • Improve the application server and direct connection performance
Databases and Operating System support
  • ArcGIS 9 supports  four databases, DB2, Informix, Oracle 8i to 10G and SQL Server.O/S support is for Window, Unix, Linux and Solaris.
  • They now support raster formats L277 and JPEG 2000.
  • Pyramids now allow for partial creation and will build pyramids only for the area loaded/unloaded. *(See definition at end of this document).
  • Log files - database log file in previous versions became very large and difficult to manage.This area has been improved so that SDE now owns a pool of log files.
  • Support for OGC's "well known binary format" (WKB), WKB geometries, 2D simple features and 3D.
  • Better database compression and related rules for compression
  • ArcSDE now has an API trace tool for developers - traces API calls
  • XML support as a data type
  • A "check schema" tool to insure consistency in Metadata (Windows only)


Specific Database Improvements

DB2

  • Operating system group support
  • Multi-versioning view
  • Added additional O/S support for Linux Enterprise Server, Solaris & AIX
Informix
  • Multi-versioning view
  • Improved versioning model
  • Faster
  • Support to version 9.4 UC3
Oracle
  • Performance in server speed (versions less than 10)
  • Oracle 10G support (does not take advantage of 10G spatial functions, and they treat 10G the same as version 9.0)
  • Added a "Check Feature command" to validate spatial data (validates the Geometry)
SQL Server
  • Single spatial database model
  • Windows Group support
  • Increased performance
  • Increased security
  • Metadata is now in a single SQL Server database (a single SDE database holds all the metadata, for all objects regardless of actual database location)
  • Users can connect to one database and access all others if they have permission
  • Simplified administration
Other functions in the ArcGIS 9 Geodatabase
  • XML support for Geodatabases
    • For import/export
    • To allow schema and data interchanges
    • Can use XML to export changes in the geodatabase
    • Can use XML to export geodatabase features
  • Interoperability Connector
    • Safe Software's FME tools for connection to disparate data without conversion
  • Geodatabase raster support
    • Supports raster catalogs
    • Raster datasets
    • Raster as an attribute column
    • Raster in the enterprise and personal geodatabases
Explorations (R & D)
ESRI is exploring the use of inexpensive and file based databases as potential inclusions in the databases supported by ArcGIS 9 and beyond geodatabases.

Concepts in Geodatabase Design
Database design does not usually share the glamor of 3D imagery or watching a feature layer drape over a topographical representation.However, with large datasets the database design is similar to the concept of having a good foundation when erecting a new building.

This function requires significant thought and understanding of the data structures you will be using.The ten steps below are taken from a new (August 2004) ESRI publication Designing Geodatabases.This book was written by David Arctur and Michael Zeiler (ESRI), and their ten steps for design are presented here to give you an appreciation of not only the design of geodatabases, but also how the above improvement in ArcGIS 9 Geodatabases can affect the design and implementation of geodatabases.

See also...www.support.esri.com/datamodels also http://arcscripts.esri.com/

[ Color Key: Light Blue = Conceptual Design, Orange = Logical Design, Red = Physical Design]

  1. Identify the information products that will be produced with your GIS -- Inventory map products, analytical modest, database reports, Web access, data flows and enterprise requirements
  2. Identify the key thematic layers based on your information requirements -- Specify the map use, data source, spatial representations, map scale and accuracy, and symbology and annotation.
  3. Specify the scale ranges and spatial representations for each thematic layer -- GIS data is compiled for specific scale use; feature representation often changes between point, lines and polygons at larger scales.Rasters are sampled to include multi-resolution pyramids.* (See pyramid definition)
  4. Group representations into datasets -- Discrete features are modeled with feature datasets, feature classes, relationship classes, rules and domains.Continuous data is modeled with raster datasets.Measurement data is modeled with survey datasets.Surface data is modeled with raster and feature datasets.
  5. Define the tabular database structure and behavior for descriptive attributes -- Identify attribute fields, specify valid values and ranges, apply subtypes to control behavior, and model relationships.
  6. Define the spatial properties of your datasets --Use networks for connected systems of features and topologies to enforce spatial integrity and shared geometry.
  7. Propose a geodatabase design -- Make informed decision on applying structural elements of the geodatabase and prepare a design.Study existing designs for examples.
  8. Implement, prototype, review and refine your design -- From the initial design, build a geodatabase and load data. Test and refine your designs.
  9. Design work flows for building and maintaining each layer -- Each layer has distinct data sources, accuracy, currency, metadata and access.Define workflows to conform to your agency's business practices.
  10. Document your design using appropriate methods -- Use drawings, layer diagrams, schema diagrams and reports to communicate your data model.


Summary
The concepts of geodatabase design is complex and requires a substantial amount of work to tie GIS products, middle ware and relational databases together.Today, because of the interaction of government, free enterprise and GIS vendors to provide multi-platform solutions and commonality in data access, these designs become even more important.Web services, mobile computer and a whole host of innovations also affect data access.The data foundation that is built, perhaps while not as glitzy as 3D, holographic geographic displays and fly throughs, is really the means that allows those things to be useful.

* Definition - Raster Pyramids (Source: From the ESRI Web Site)

When a raster has to be represented in a series of reduced/increased resolutions, a "pyramid" is built for that particular raster.A pyramid is a series of reduced resolution representations of the dataset, mainly used to improve the display performance of rasters when one is not working with the pixel information at full resolution.It contains a number of layers, each re-sampled at a more generalized level.Thus each level of the pyramid is a re-sampled representation of the raster at a coarser spatial resolution.


Your Comments
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Raster Pyramids (#1)
by Nancy Richwine, PA Department of Agriculture
   
Date: August 25, 2004 15:11 PM
I havent't worked with rasters much yet and never quite understood what pyramiding was before now. Thanks!

AYUDA (#2)
by MILENA, INDEPENDIENTE
   
Date: September 30, 2004 11:48 AM
PORVOR NECESITO AYUDA. ACTUALMENTE ME ENCUENTRO TERMINANDO MI PROYECTO DE GRADO Y DEBO REALIZAR EL DISEÑO DE UNA BASE DE DATOS PARA UN SISTEMA DE INFORMACION GEOGRAFICA Y ESTOY UN POCO CONFUNDIDA.
LE AGRADEZCO SU COLABORACION.


Oracle Spatial vs ArcSDE (#3)
by Prasenjit Bhattacharyya, Spatial Solutions
   
Date: May 23, 2005 06:54 AM
Dear Mr Reid,

We are implementing an enterprise GIS with ArcGIS platform and Oracle as the Database. The problem which has arrived is that we are not sure which software to take for Application Server - Oracle Spatial or ArcSDE. We are now thinking of buying both and using both of them. I need some inputs as to where we should be using Oracle Spatial and where we should use ArcSDE

My email address is ceo@spatialsolutions.org

Regards

Prasenjit


Oracle Spatial and ArcSDE (#4)
by Jim Bellanger, Aera Energy LLC
   
Date: July 20, 2005 00:34 AM
Mr. Reid, I have a similar situation as Mr. Bhattacharyya. We currently have a GIS implementation but are now expanding it to an enterprise level including a GEO reporting database. We currently use ArcSDE and are licensed for Oracle Spatial. What are the advantages or disadvantages of integrating these products?

Many thanks in advance
jim


Ayuda en español (#5)
by Nestor, hidrologico sureste
   
Date: August 22, 2005 11:13 AM
Milena te recomiendo que visites este site que es en español y me esta ayudando en bastante grado http://recursos.gabrielortiz.com
desde ya saludos


GeoDatabases distribuidas (#6)
by Alfonso Andres, Estudiante
   
Date: December 2, 2005 12:05 PM
Hola: estoy haciendo un trabajo con bases de datos geograficas distribuidas, y buscando por web solo encuentro temas comerciales de aplicaciones espaciales para bases de datos.
Quisiera saber si alguien sabe donde puedo encontrar informacion mas tecnica sobre este tema:

Formas de uso y creacion de Geodatabases distribuidas.

Un saludo y muchas gracias


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