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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
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 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
databases
“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 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 terminology1
New Terminology
  • Feature Class
    • Data for one layer of vector data
    • Points, Polyline, or Polygon
    • Has spatial data, attributes, metadata
    • Effectively, a 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

references
References
  • 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.
  • In Digital Earth or dusk.geo.orst.edu/djl/arcgis/book.html
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