Problem with gis data
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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

  • 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

  • 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

  • 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


Esri Approach


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

  • 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

  • Definition for a complex set of data

  • Stored in a Geodatabase

  • Easily shared

Data Model in a “Can”


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

  • In Memory

    • Loaded in ArcGIS

  • In File

    • Traditional Files:

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

    • Network Files:

      • Links to download

      • Web services

    • 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 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

  • 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 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


The “Can”


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


GDB with Feature Dataset


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


Feature Class vs. Shapefile


File Geodatabase Structure

  • Disk

    • Folders…

      • Geodatabase.mdb

        • FeatureSet

          • FeatureClass


Data Color-coding

yellow coverage

green shapefile

gray geodatabase


Esri Data Models


Graphic courtesy of Maidment et al., ArcHydro team


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


Geodatabase Feature Class Geometries


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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