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Introduction to the Geodatabase

Introduction to the Geodatabase. What is a Geodatabase? What are feature classes and feature datasets? What are domains Design a personal Geodatabase Import data to a Geodatabase. What is a Geodatabase?. A relational database that contain geographic information.

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Introduction to the Geodatabase

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  1. Introduction to the Geodatabase

  2. What is a Geodatabase? • What are feature classes and feature datasets? • What are domains • Design a personal Geodatabase • Import data to a Geodatabase

  3. What is a Geodatabase? A relational database that contain geographic information • A container for tables, feature classes, feature datasets…. • Tables – attributes of rows and columns • Standalone feature classes (conceptually like shape files) • Feature datasets (a collection of feature classes) • Rules and relationships

  4. Feature classes….. • Store geographic features represented as points, lines, or polygons, and their attributes; • Can also store annotation and dimensions. • Tables may contain additional attributes for a feature class

  5. Feature datasets….. • Feature classes can be organized in Feature datasets. • All feature classes in a feature dataset share the same coordinate system. • Feature classes in a feature dataset can be organized into a geometric network. The network maintains topological relationships between its feature classes.

  6. Personal vs. Multiuser Geodatabase Personal geodatabase - stores data in a Microsoft Access database - size limit 2 GB - directly read through ArcCatalog - does not support raster data Multiuser geodatabases - data stored in IBM DB2, Informix, Oracle, or Microsoft SQL Server - connected through ArcSDE or direct - ArcSDE license necessary for editing - supports raster data

  7. Why Geodatabase? • All data (vector, raster, address, measures, CAD, etc.) is stored together in a commercial off-the-shelf DBMS • Simplify support and maintenance, and reduce costs • Allows multi-user access (with ArcSDE license) • Support for intelligent features, rules, and relationships between feature classes

  8. More advantages….. • Dynamic Geocoding • Annotation subclasses • Subtypes within Feature classes • Coded attribute and range domains • Improved topology and editing

  9. Confused? • The geodatabase may seem complicated….. …however they are simply modern equivalents of shapefiles and coverages stored in a commercial database.

  10. Geodatabases in ArcGIS • - Geodatabases can be created and managed easily using the standard tools in ArcCatalog • ArcMap and ArcToolbox provides tools to work with geodatabases

  11. Creating a Geodatabase Think before you create • Design process • Create an empty Geodatabase in ArcCatalog • Define the database structure • Set spatial reference and coordinate domains • Load data • Define topology rules and relationships

  12. Design process • What data layers to include in the geodatabase • Shape files – Coverages • Look-up tables • How to organize the feature classes into logical feature datasets • Think about what topolygy rules you may want to apply – how are the feature classes related to each other spatially?

  13. Create a new Geodatabase in ArcCatalog

  14. Migrating existing data into the Geodatabase • Shape files and coverages are converted to feature classes • Attributes can be left out or renamed • CAD data, dBase files, annotation etc. can be imported • Data of the same spatial extent can be imported to the same feature dataset

  15. Importing existing data • In ArcCatalog or ArcToolbox • Tools and wizards are available • Works with coverages, shapefiles, tables, CAD etc.

  16. Creating Feature Datasets • Right-click on the geodatabase – New – Feature Dataset • Name the Feature Dataset and define the coordinate system • Set X/Y domain • Set Z domain and M domain • Set manually or import from existing data sets

  17. Coordinate Domains Lost data Max X and Y is 2.14 billion Y Large area Smaller precision (1,000) Small area larger precision (100,000) X (0,0)

  18. Coordinate Domains • The coordinate domain defines the area you can make edits in • X and Y max is 2.14 billion for the database • Default domain is 21000, 21000 • Define your coordinate domains correctly the first time – they cannot be changed • You can have a different coordinate domain for each feature class

  19. What is max/min X and Y on the map? Max X and Y Min X and Y

  20. Setting X/Y Domain Precision 1000 Min X ~ 2,145,320 Max X ~ 2,657,580 Min Y ~ 1,632,610 Max Y ~ 1,967,940 1 ft units, 1/1000 ft accuracy Precision = 1000/1 = 1000 (good enough)

  21. Coordinate Domains Max X and Y is 2.14 billion Y Most of the data is here in the database Large expansion options to the north and east X (0,0)

  22. Coordinate Domains Calculations Min X ~ 2,145,320 Max X ~ 2,657,580 Min Y ~ 1,632,610 Max Y ~ 1,967,940 Precision 1000 These coordinates would put the data in the lower left corner – however we want to shift this to be able to expand in all directions (MinX + MaxX)/2 – (2.14 x 109) / (1000 x 2) = X min 2,401,450 – 1,070,000 = 1,331,450 (MinY + MaxY)/2 – (2.14 x 109) / (1000 x 2) = Y min 1,800,275 – 1,070,000 = 730,275

  23. Coordinate Domains Calculations (MinX + MaxX)/2 + (2.14 x 109) / (1000 x 2) = X max 2,401,450 + 1,070,000 = 3,471,450 (MinY + MaxY)/2 + (2.14 x 109) / (1000 x 2) = Y max 1,800,275 + 1,070,000 = 2,870,275 Shifted x/y domain Default x/y domain Min X = 1,331,450 Max X = 3,471,450 Min Y = 730,275 Max Y = 2,870,275 Precision 1000 Min X ~ 2,145,320 Max X ~ 2,657,580 Min Y ~ 1,632,610 Max Y ~ 1,967,940 Precision 1000

  24. Coordinate Domains Max X and Y is 2.14 billion Y Most of the data is here in the database Large expansion options in all directions X (0,0)

  25. The shifted x/y domain allows for editing within this window Max X, Max Y Min X, Min Y

  26. Why create Feature Datsets? • Data organization • Topology rules • Shared boundaries • Geometric networks

  27. Subtypes in feature classes Subtypes can only be created in ArcEditor and ArcInfo - A subtype is a group of objects that have similar properties within the Geodatabase For example the attribute ‘ZoneCode’ may have subtypes: - Commercial, Residential, Industrial Landcover vegetation types may have subtypes: - Forest, Agriculture, Rangeland, Urban

  28. Attribute Domains • Attribute domains are properties of the Geodatabase • - Multiple objects may use the same domain • - Can be created using the Domains properties dialog box • Defines legal values for field attributes • - Range domains (allowable numeric value range) • - Coded value domain (in dropdown menus)

  29. Questions?

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