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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.

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Problem with GIS Data

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  1. 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: • ?

  2. 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

  3. 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

  4. Data Modeling

  5. Esri Approach

  6. Data Complexity • Shapefile: • shp: spatial data • dbf: attributes • shx: index • xml: metadata • prj: SRS • Would be nice if this was all in one file

  7. 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

  8. Esri Data Models • Definition for a complex set of data • Stored in a Geodatabase • Easily shared Data Model in a “Can”

  9. 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

  10. 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

  11. “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

  12. 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

  13. 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

  14. 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

  15. New File Geodatabase

  16. The “Can”

  17. 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

  18. New Feature Dataset

  19. GDB with Feature Dataset

  20. New Terminology • Feature Class • Data for one layer of vector data • Points, Polyline, or Polygon • Has spatial data, attributes, metadata • Effectively, a shapefile

  21. New Feature Class

  22. Feature Class vs. Shapefile

  23. File Geodatabase Structure • Disk • Folders… • Geodatabase.mdb • FeatureSet • FeatureClass

  24. Data Color-coding yellow coverage green shapefile gray geodatabase

  25. Esri Data Models

  26. Graphic courtesy of Maidment et al., ArcHydro team

  27. Arc Marine dusk.geo.orst.edu/djl/arcgis

  28. Geodatabase Feature Class Geometries

  29. 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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