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The Geodatabase

The Geodatabase. Geodatabase Fundamentals. Spatial data formats Geodatabase data structure Personal vs. enterprise geodatabase Components of geodatabase Building geodatabase. Geographic Feature Data Formats.

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The Geodatabase

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  1. The Geodatabase GISC 6382 Applied GIS UT-Dallas Briggs

  2. Geodatabase Fundamentals • Spatial data formats • Geodatabase data structure • Personal vs. enterprise geodatabase • Components of geodatabase • Building geodatabase GISC 6382 Applied GIS UT-Dallas Briggs

  3. Geographic Feature Data Formats • Formats are based on representations (models) of the real world that can be placed in a GIS to produce maps, perform interactive queries, and execute analyses. • CAD – first computer mapping model/format. • Binary file format with little attribute information. • Coverage – native ArcInfo 7 format. • Based on Georelational data model. • Vector data is maintained in indexed binary files and partitioned from, but linked to attribute tables by a common identifier. • Topological relationships are maintained. • Shortcomings – features aggregated into collections of points, lines & polygons with generic behavior. The behavior of a line representing a road is the same as the behavior of a line representing a stream. GISC 6382 Applied GIS UT-Dallas Briggs

  4. Geographic Feature Data Formats • Shapefile – introduced with ArcView • Also georelational data model – nontopological vector data format. • Very prolific format – much GIS data in Shapefile format. • Simpler than coverage because they do not store topological associations among different features and feature classes. • Limited analysis capabilities due to lack of topology • Geodatabase – introduced in ArcInfo 8. • Object-oriented model – can characterize features more naturally by defining object types, topological, spatial and general relationships, and interactions. • Geodatabase features can be stored in a single database. • Create custom features in addition to points, lines, polygons • Brings physical model closer to logical model. GISC 6382 Applied GIS UT-Dallas Briggs

  5. Supported Data Types • ArcInfo 8 supports four representations of geographic data. • Vector data for representing features. • Raster data for images, grids, and surfaces. • Triangulated irregular networks (TINS) for surfaces. • Tabular data. • Locators and addresses for finding a geographic position from an address. • Locators apply national postal conventions to convert an address to a position. • Note: in AI8.1, geodatabases do NOT store TINS. They must be kept in coverage workspaces. GISC 6382 Applied GIS UT-Dallas Briggs

  6. What is a Geodatabase? • A new type of geographic data format (GDF) for ArcInfo 8. • Based on Object-Oriented Model • Users can add behavior, properties, rules and relationships to data • Implemented as extension to standard relational database technology • Supports topologically integrated feature classes • Extends the coverage model with support for complex networks, relationships among feature classes, and other object-oriented features • Provides platform for development of custom data models using visual tools like CASE (Computer Aided Software Engineering) tools and UML (Unified Modeling Language) notation GISC 6382 Applied GIS UT-Dallas Briggs

  7. ArcCatalog Is the Principal User Interface Used to Define and Manage the Geodatabase GISC 6382 Applied GIS UT-Dallas Briggs

  8. ArcCatalog ArcMap Geodatabase Framework GISC 6382 Applied GIS UT-Dallas Briggs

  9. Personal (single-user) Geodatabase • Personal Geodatabase. • Implemented as a Microsoft Access database (*.mdb file) by using MS jet engine which is installed with AI8. MS access is not needed. • Can be placed on local or network drives. • Generally used for personal or small work-group use. • Can handle small to moderately sized datasets. • Personal geodatabase can yield decent performance for datasets of 250,000 objects or less, maximum size is 2.0 GB • Full functionality of geodatabase served through ArcSDE except versioning. • Versioning – allows many editors to work concurrently and includes framework to resolve edit conflicts. • If a personal geodatabase is deleted its gone. GISC 6382 Applied GIS UT-Dallas Briggs

  10. Enterprise (Multi-user) Geodatabase • ArcSDE Geodatabase • ArcSDE is the multi-user data access extension to ArcInfo (bundled w/software) that serves geodatabases to AI applications running on pc’s on TCP/IP network. • Used for demanding datasets requiring concurrent editing by multiple users. • Created by installing a DBMS and ArcSDE on a server. • ArcCatalog only creates and deletes connections to ArcSDE geodatabases. • Can be deployed on UNIX or Windows NT. • Many use UNIX platform for ArcSDE and DBMS and NT for AI applications • ArcSDE is centrally tuned and managed by a DBA. • Can build SQL applications to access tables in a remote geodatabase. GISC 6382 Applied GIS UT-Dallas Briggs

  11. Geodatabase Elements • Objects & Object classes • Features & Feature classes • Feature datasets • Spatial references • Domains • Subtypes • Relationships & Relationship classes • Geometric networks • Labels and Annotation GISC 6382 Applied GIS UT-Dallas Briggs

  12. Objects & Object Classes • Geodatabases organize geographic data into a hierarchy of data objects. • Objects are instances of an object class that have properties and behavior. • Objects can be related to other objects via relationships • Objects have unique system identifiers (OID) • Object classes are tables in a geodatabase storing non-spatial data (e.g., Parcel owners) • Objects in an object class have the same • Properties - stored in the table as attributes • Behavior - implemented as a component GISC 6382 Applied GIS UT-Dallas Briggs

  13. Object Classes (tables) A row stores an Object GISC 6382 Applied GIS UT-Dallas Briggs

  14. Features and Feature Classes • Features are objects with required shape (Points, Multi-points, Lines & Polygons) that represent a real world object in a layer on a map. • Features classes are collections of features with same type of feature geometry and attributes. • A feature class is also an object class which stores spatial objects (features) (e.g., Parcels). • All the features in a feature class are in the same spatial reference. • Feature classes which store topological features must be contained within a feature dataset to ensure a common spatial reference. GISC 6382 Applied GIS UT-Dallas Briggs

  15. Feature Classes Feature Class Table A row stores feature BLOB: Binary Large Object Block GISC 6382 Applied GIS UT-Dallas Briggs

  16. Feature Datasets • Containers for feature classes • Shared spatial reference • Analogous to a coverage • less restrictive • May also contain • relationship classes • geometric networks • Annotations GISC 6382 Applied GIS UT-Dallas Briggs

  17. Building a Geodatabase Design geodatabase • Building a geodatabase • Designing the geodatabase • (Think before your create) • Creating a new geodatabase • (Name and location only) • Defining the geodatabase structure • (Schema and data) • Entering spatial data • (Loading or automation) • Define additional properties • (Validataion, relationships, networks) Create a new geodatabase Defining GDB structure Geodatabase Entering spatial data Define additional properties GISC 6382 Applied GIS UT-Dallas Briggs

  18. Designing a Geodatabase • Conceptual Plan: Current and future needs • Data contents • Coordinate system • Data validation and modification rules • Relationships among objects • Custom objects • Logical Design • Can use CASE tools • What needs to store (Not how to store) • UML Use Case • Microsoft Visio Enterprise Edition Microsoft Visio Enterprise Version GISC 6382 Applied GIS UT-Dallas Briggs

  19. Creating a New Geodatabase • Create a new geodatabase using ArcCatalog • Create new • Rename default name GISC 6382 Applied GIS UT-Dallas Briggs

  20. Defining Geodatabase Structure • Create from scratch manually. • Use tools in ArcCatalog to create schema • Importing existing database schema • Can convert by importing schema from existing datasets • Use CASE tools and UML to automate database creation. • Can use CASE tools to create new custom objects and/or generate a geodatabase schema from UML • CASE (Computer Aided Software Engineering) • UML (Unified Modeling Language) GISC 6382 Applied GIS UT-Dallas Briggs

  21. Create schema from scratch manually • Define structure using ArcCatalog • Feature datasets • Feature classes • Tables • Relationship classes • What to Define? • Database name • Field name and properties • Spatial reference • Table relationship parameters GISC 6382 Applied GIS UT-Dallas Briggs

  22. Importing existing database schema • Import data and/or database schema • Shape files, coverage, features class • INFO, dBase tables • Options while importing • Rename object • Rename or exclude attribute columns • Modify spatial reference • Insert feature class into feature dataset GISC 6382 Applied GIS UT-Dallas Briggs

  23. Use CASE tools and UML to define database structure • Physical Design using UML • Feature class, relationship class, subtype and/or domain schema • Design large database with visualization and documentation of data relationship and attributes • Edit ESRI Object Model diagram • Create customize objects inherited from ESRI objects (ArcObjects) • Export structure to Microsoft Repository, then to ArcCatalog • Visual Basic with GIS Applications (Visual Basic + MapObjects), Substitute Computer Techniques • GIS Application Software Development (ArcObjects + UML) GISC 6382 Applied GIS UT-Dallas Briggs

  24. Entering Spatial Data • Spatial data automation options • Analog data: digitizing or scanning • Arc/Info formats: importing and loading • Other digital data: data conversion • Data Mapping • Vector geometry types (p. 81) • X, Y: Points, multipoints, lines, polygons • Z: Optional position in Z (e.g. elevation) • M: Optional linear measurement (e.g. milepost) • Field mapping (p. 82) • Spatial Reference GISC 6382 Applied GIS UT-Dallas Briggs

  25. Importing Vs. Loading • Importing • Creates new features within a new feature class or geodatabase table. • The features class or table cannot exist before importing • Database schema is imported at the same time • Loading • Appends features into an existing feature class. • Existing feature class have the same schema with the data sources • Simple Data Loader (ArcCatalog) • Object Loader Wizard (ArcMap) GISC 6382 Applied GIS UT-Dallas Briggs

  26. Defining additional database properties • Leveraging geodatabase advantages • Add validation rules: subtype and domain • Define relationships between tables • Create topological structure (Geometric network) • Create annotation GISC 6382 Applied GIS UT-Dallas Briggs

  27. Spatial Reference • Spatial Reference • Coordinate system • Spatial domain • Precision • Cautions • All feature classes within a feature dataset share the same spatial reference. • Once created, the spatial domain for feature dataset/class cannot be changed. • Data outside extent of dataset need to be created in a new feature dataset or standalone feature class. GISC 6382 Applied GIS UT-Dallas Briggs

  28. Coordinate system • Projection system & parameters • Geographic, UTM and State plane • Datum, central Meridian, standard parallels, false northing and easting • Define Coordinate system for feature dataset/classes • Select: a predefined coordinate system • Import: from existing geodatabase • Create: a new coordinate system • Modify: current coordinate system • Save: for future use GISC 6382 Applied GIS UT-Dallas Briggs

  29. Spatial Domain • Spatial Domain • The allowable coordinate range for the geographic coordinates • X/Y Domain: • MinX, MaxX, MinY, MaxY • Z Domain: • Min, Max • M Domain: • Min, Max GISC 6382 Applied GIS UT-Dallas Briggs

  30. Precision • Precision • The number of system units per one unit of measure (of distance). Precision determines the resolution of a map (geodatabase) • For example: map unit is meter • Precision of 1: 1 system unit = 1 meter (resolution) • Precision of 1000: 1000 systems units = 1 meter • 1 systems unit = 0.001 meter = 1 millimeter (resolution) • E.g. Map unit feet, Precision of 12, Resolution? 12 system units = 1 foot 1 system unit = 1/12 foot = 1 inch (resolution) GISC 6382 Applied GIS UT-Dallas Briggs

  31. Determine Precision Based on Map Resolution • Formula: • Resolution = Map unit / precision • Precision = Map unit / resolution • Determine precision of a new geodatabase • Digitizing table resolution is 0.002 inches, map scales is 1:10,000, map unit is meter Geodatabase resolution = 0.002 inches * 10,000 = 20 inches 20 inches = 20 /39.37 meters = .508 meter ~ 0.5 meter Precision = 1 meter / 0.5 meter = 2 GISC 6382 Applied GIS UT-Dallas Briggs

  32. Geodatabase Storage and Precision Map units (Use) Floating Point 123.456 (m) • Coverage/Shapefile storage: • Single floating point precision (6-7 digits) • Double floating point precision (13-14 digits) • Geodatabase storage • As Integer: 4 byte integer • Stores 2.14 billion system units • max = 2,147,483,648 • Coordinate are • Multiplied by precision when stored • Divided by precision when used Multiply by precision 123.456*1000 Divide by precision 123,456/1000 System units (Store) Integer 123,456 GISC 6382 Applied GIS UT-Dallas Briggs

  33. 4 billion 200,000,000 mm x 3,750,000,000 mm y 2 billion 2 billion Check Geodatabase Precision with Range • Range in Map Unit (RangeMU) • Larger of width or height • Width = MaxX –MinX • Height= MaxY – MinY • Example • 1,000,000 – 200,000 = 800,000 (Width)  RangeMU • 4,060,000 – 3,750,000 = 310,000 (Height) • Range in system unit (RangeSU) • RangeSU = RangeMU * Precision • RangeSU = 800,000 * 1000 = 800,000,000 < 2.14 billion • Is OK to accept 1000 as precision? GISC 6382 Applied GIS UT-Dallas Briggs

  34. Re-center Coordinates using shift • Problem: • At desire precision, data is outside extent • Solution • Shift the center of geodatabase space to the center of the data • Shift = the difference between the center of your data and GDBCenterMU • Formula: • Center of geodatabase space in map units (GDBCenterMU) • (2,147,483,648/2)/precision = (2,147,483,648/2)/1000=1,073,741.824 • Center of your data • (DataMinX + DataMaxX)/2 and (DataMinY + DataMaxY)/2 • Shift • ShiftX = (DataMinX + DataMaxX)/2 – GDBCenterMU • ShiftY= (DataMinY + DataMaxY)/2 – GDBCenterMU • Update (MinX, MinY) with (ShiftX, ShiftY) GISC 6382 Applied GIS UT-Dallas Briggs

  35. 4 billion 200,000,000 mm x 3,750,000,000 mm y 2 billion 2 billion Geodatabase Storage and Shift Map units (Use) Floating Point 3,000,000.456 (m) • The geodatabase will • Subtract shift, then multiply coordinate by precision when stored • Divide coordinates by precision, then add shift when used Add shift 1,000,000.456 + 2,000,000 Subtract shift (3,000,000.456 – 2,000,000) Multiply by precision 1,000,000.456*1000 Divide by precision 1,000,000,456/1000 System units (Store) Integer 1,000,000,456 GISC 6382 Applied GIS UT-Dallas Briggs

  36. Subtype and Attribute Domain • Subtype • Attribute domain • Rang domain • Coded value domain • Associating domain with subtype • Attribute validation rules • Split and merge domain policies GISC 6382 Applied GIS UT-Dallas Briggs

  37. Why Subtypes and Attribute Domains • Data Integrity • Prevent illegal attribute assignment to features, tables with out-of-range data values • For certain critical field, provide predefined codes as the only valid values • Data Efficiency • Associate different subset of a feature class with different default values, attribute validation rules • Allow efficient choice from a set of valid value descriptions rather than manually input the value itself PowerPoles Streets Wood Steel Primary Secondary 20-30 30-50 ST, RD, AV, BLVD Ln, Cir, Pl GISC 6382 Applied GIS UT-Dallas Briggs

  38. Subtype • Subtype • Feature class’ “subclasses” that allow you to further distinguish objects without creating new feature classes • Logical groups of a subset of records within a feature class based on single column’s values • Same subtype has similar attribute values and behaviors • Create Subtype • Can choose default subtype • Require integer values (long/short), user adds descriptions • Can have different default values and domains for each field to improve data efficiency GISC 6382 Applied GIS UT-Dallas Briggs

  39. Creating Subtypes 1 • Define subtypes using ArcCatalog • For feature class or table properties • Select column to create subtype • Enter subtype code and description • Enter default values and domains for each subtype • Set default subtype 4 2 3 GISC 6382 Applied GIS UT-Dallas Briggs

  40. Display and Edit Subtypes in ArcMap • Displaying • Subtype can have unique classification • Subtype descriptions are listed in TOC • Symbols can be modified as desired • Adding new features • Use Editor Target list to add feature with chosen subtype • Editing existing features/records • Can apply subtype after data entry • Subtype fields shows description, not code • Changing the subtype updates the default values for other fields GISC 6382 Applied GIS UT-Dallas Briggs

  41. Domain • Define a set of legal values for a field’s attributes • Range: specifies a valid range of values for a numerical attributes • A water pipe must be between 1 and 100 inches wide • Coded value: specifies a valid set of values for an attributes. Can apply to any type of attributes • Parcels can only have RES or VAC land use values • Validation methods • Pulldown list of descriptions (coded values) prevents error • Validation during edit session prevents range error • A geodatabase property • Can apply to entire field or individual field subtype • Multiple objects in the same database may use the same domain • Cannot edit domain referenced by another subtype GISC 6382 Applied GIS UT-Dallas Briggs

  42. Creating Range Domains • Click on existing or blank domain • Enter the name and description for the domain • Enter the domain prosperities • Field type • Domain type: Range • Minimum value • Maximum value • Split policy • Merge policy 1 2 3 GISC 6382 Applied GIS UT-Dallas Briggs

  43. Creating Coded Value Domains • Click on existing or blank domain • Enter the name and description for the domain • Enter the domain prosperities • Field type • Domain type: Coded Values • Split policy • Merge policy • Enter the coded values • Code • Description 1 2 3 4 GISC 6382 Applied GIS UT-Dallas Briggs

  44. Associating domains to entire fields • Provide validation for records within a specified field • Domain must be defined as same field type Diameter_L is float Only float domain appear GISC 6382 Applied GIS UT-Dallas Briggs

  45. Associating domains to subtype • Provide validation for records within subtype • Domain must be defined as same field type Subtype field grouped into four codes Each code has its own domain for other attributes GISC 6382 Applied GIS UT-Dallas Briggs

  46. Editing records that have coded value domains • ArcMap only shows valid domain description • View codes in table by changing the appearance of the table GISC 6382 Applied GIS UT-Dallas Briggs

  47. Editing records that have range domains • Perform edit in ArcMap • Validate selection verifies fields with a range domain • Invalid features remain selected Angle has a range domain of 0 -359 GISC 6382 Applied GIS UT-Dallas Briggs

  48. Split Domain policies • Split policies on edited feature’s attribute default value geometric ratio duplicate Split Policy GISC 6382 Applied GIS UT-Dallas Briggs

  49. Merge Domain policies • Merge policies on edited feature’s attribute Merge Policy default value sum values weighted average GISC 6382 Applied GIS UT-Dallas Briggs

  50. Table Association and Table Join • Table association • Attributes about a feature can be stored • Feature class table (Feature class) • Separate table (Object class) • Associate tables with common column (key) values • Primary keys: Common field on original table • Foreign keys: Common field on destination table • Table join • Merge two tables together into one table logically or physically (in ArcMap). GISC 6382 Applied GIS UT-Dallas Briggs

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