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Attribute Data Input and Management

Attribute Data Input and Management . Chapter 6. Introduction. Spatial and attribute Attribute data are stored in tables Georelational data model stores spatial and attribute data in separate files, linked by feature id. Synchronized.

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Attribute Data Input and Management

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  1. Attribute Data Input and Management Chapter 6

  2. Introduction • Spatial and attribute • Attribute data are stored in tables • Georelational data model stores spatial and attribute data in separate files, linked by feature id. • Synchronized. • Object-oriented data model stores spatial and attribute data in a single database. • No need to synchronize

  3. Attribute Data in GIS • Georelational data model links spatial data and attribute data by id. • Attribute data stored in feature atttribute table which contains the id. • Row is called a record, column is called a field or an item. • Database management system (DBMS) • Info, dBase, Oracle, Informix, SYBASE, Access, FoxPro, SQL Server, etc. • Object-oriented embeds GIS into database

  4. Types of Attribute Data • Character, integers, floating points (or real numbers), dates, time intervals. • Measurement scale • Nominal (named) • Ordinal (ordered by some attribute) • Interval (known interval such as degree) • Ratio (based on meaningful absolute zero) • Categorical (n and o); Numerical (i and r)

  5. Types of Attribute Data • Data types and measurement scales are closely related. • Character for nominal and ordinal • Integers and real for interval and ratio, depending on decimal needs • Most GIS can convert numbers to characters and vice versa. • Watch! Normally text left, number right justified

  6. Relational Database Model • Flat file (ascii or txt) • Hierarchical database (family tree example) • Network database (connections developed) • Relational • Key • efficient, independent, temporary link

  7. Relational Database Model • Constructing a relational database • Why? • General ideas. • Sample of Northwind with Microsoft Access on your computer. • Normalization

  8. Types of Relationships • One-to-one • One-to-many • Many-to-one • Source table • Destination table

  9. Attribute Data Management Using ArcView • Two functions • join (one table) • link (both tables remain • virtual tables

  10. Attribute Data Management Using ARC/INFO • JOINITEM • one-to-one • many to one • permanent • exactly same item key • RELATE • one-to-one • many to one • temporary • CURSOR for “link-like”

  11. Attribute Data Entry • Field definition • data width • data type (must match GIS package) • number of decimal places • include spaces for negative sign and decimal point • Methods of data entry • avoid manual • import if possible

  12. Attribute Data Entry Methods of data entry • UPDATE (one record at a time!) • look up table • take advantage of relational data model • use user-friendly cut and paste and then import

  13. Attribute Data Verification • Woe is me! • Linked to spatial data • Accuracy of attribute data • Range and validity checking • Printing • Re-entry and compare • Expert spot check

  14. Creating New Attribute Data from Existing Data • Simplify by reclassification • new field • select and fill • repeat • Attribute data computation • computation • weighting

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