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Problem with GIS Data. Lots of different, related files Results in data that is: Hard to find and share and of questionable quality Need: Containers for datasets: File Geodatabases? Standards for complex data: Data Models? Protocols for maintaining quality: ?. Data Structure.

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Problem with GIS Data

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Problem with gis data

Problem with GIS Data

  • Lots of different, related files

  • Results in data that is:

    • Hard to find and share and of questionable quality

  • Need:

    • Containers for datasets:

      • File Geodatabases?

    • Standards for complex data:

      • Data Models?

    • Protocols for maintaining quality:

      • ?

Data structure

Data Structure

  • Defines the “structure” of the data

  • A container for specific types of data

  • Can contain data of different meanings

  • For files, synonymous with “Format”

  • Examples:

    • Shapefile: Point, Polyline, Polygon

    • TIFF: Raster

    • Text file: Tables

    • XML: Metadata

Data model

Data Model

  • Defines the contents and meaning of the data

  • Should be detailed enough for someone else to use the data

  • Examples:

    • Tiger Census files

    • NHD watersheds

    • Landsat Image

    • GNIS Data

    • FGDC Metadata

Data modeling

Data Modeling

Esri approach

Esri Approach

Data complexity

Data Complexity

  • Shapefile:

    • shp: spatial data

    • dbf: attributes

    • shx: index

    • xml: metadata

    • prj: SRS

  • Would be nice if this was all in one file

Sharing tools

Sharing Tools

  • Won’t it be great if we could use tools like model builder to work on the city of Corvallis, then use the same tools to work on the city of Albany, etc.

  • Need a common format for all the spatial data

    • Roads, rail lines, parks, water mains, parcels, hydrants, zoning areas, etc

Esri data models

Esri Data Models

  • Definition for a complex set of data

  • Stored in a Geodatabase

  • Easily shared

Data Model in a “Can”

Computer based data storage

Computer-Based Data Storage

  • Computers have 2 places to store data:

    • Dynamic Random Access Memory (RAM)

      • “In Memory”

      • Goes away when the power goes off

    • “Static” RAM, Disks, Tapes

      • “In Files”

      • Does not go away when the power goes off

      • Goes away when your “disk” crashes

      • Examples

        • Memory/Thumb “sticks”

        • Network drives

        • Local drives

        • “Floppy” discs

Gis data access

GIS Data Access

  • In Memory

    • Loaded in ArcGIS

  • In File

    • Traditional Files:

      • Shapefiles, TIFF, IMG, MXD, EOO, PRJ…

    • Network Files:

      • Links to download

      • Web services

    • Databases



  • Flat-File Database

    • No relationships

    • Single-user access

    • One file

    • Examples: MS-Access (mdb file)

  • Relational, Enterprise Level Databases

    • Multi-Access

    • Runs as a “Service” on a “Server”

    • Examples: Oracle, MS SQL Server, PostgreSQL, MySQL

Esri approach1

ESRI Approach

  • Create their own database structure within a database

    • Add user’s data into the Esri structure

  • Personal File Geodatabase

    • MS-Access

    • Not supported in the future

  • Relational Databases

    • Supported through Arc Spatial Database Engine (ArcSDE)

  • File Geodatabases

File geodatabase

File Geodatabase

  • Folder with “.gdb” extension!

  • Additional data types & capabilities:

    • Relationships

    • Topology Rules

    • Feature Dataset

    • Raster Catalog & Mosaic

    • Networks

  • The default for data created from the tool box

File geodatabase1

File Geodatabase

  • Advantages:

    • Easy to share complex vector datasets

  • Disadvantages:

    • Internal structure is hidden

    • Basically, only supported by Esri products

    • Raster databases can be huge

  • Note:

    • Geodatabases used to be the only way to fix topology problems, now they can be fixed with shapefiles as well

New file geodatabase

New File Geodatabase

The can

The “Can”

New terminology

New Terminology

  • Feature Dataset

    • Set of vector data (points, polylines, polygons)

    • Common SRS

  • Raster Dataset (not recommended)

    • Set of rasters

    • Common SRS

  • Name should include SRS

    • WGS84

New feature dataset

New Feature Dataset

Gdb with feature dataset

GDB with Feature Dataset

New terminology1

New Terminology

  • Feature Class

    • Data for one layer of vector data

    • Points, Polyline, or Polygon

    • Has spatial data, attributes, metadata

    • Effectively, a shapefile

New feature class

New Feature Class

Feature class vs shapefile

Feature Class vs. Shapefile

File geodatabase structure

File Geodatabase Structure

  • Disk

    • Folders…

      • Geodatabase.mdb

        • FeatureSet

          • FeatureClass

Data color coding

Data Color-coding

yellow coverage

green shapefile

gray geodatabase

Esri data models1

Esri Data Models

Problem with gis data

Graphic courtesy of Maidment et al., ArcHydro team

Arc marine dusk geo orst edu djl arcgis

Arc Marine

Geodatabase feature class geometries

Geodatabase Feature Class Geometries



  • Arctur, D. and Zeiler, M., 2004, Designing Geodatabases, ESRI Press

  • Lowe, J.W., 2003. Flexible data models strut the runway. Geospatial Solutions, 13(2): 44-47.

  • Maidment, D.R., 2002. Arc Hydro: GIS for Water Resources, ESRI Press, 203 pp. w/CD.

  • Li, X. and M.E. Hodgson, 2004. Vector-field data model and operations. GISci. Rem. Sens., 41(1): 1-24.

  • Wright, D., Blongewicz, M., Halpin, P., and Breman, J., Arc Marine: GIS for a Blue Planet, Redlands: ESRI Press, 2007.

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