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G I S DATA MANAGEMENT

G I S DATA MANAGEMENT. Data and Information are often used interchangeably, but they are distinctly different. DATA are raw, unsummarized, unanalyzed facts INFORMATION is data that have been processed into a meaningful form. KNOWLEDGE is the capacity to use the information.

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G I S DATA MANAGEMENT

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  1. G I S DATA MANAGEMENT

  2. Data and Information are often used interchangeably, but they are distinctly different. DATA are raw, unsummarized, unanalyzed facts INFORMATION is data that have been processed into a meaningful form. KNOWLEDGE is the capacity to use the information

  3. Attributes of a Data • Shareable – Readily accessed by more than one person at a time • Transportable – Easily moved to a decision maker • Secure – Protected from destruction and unauthorized use • Timely – Current and up-to-date • Relevant – Appropriate to the decision

  4. Problems with data management systems • Redundancy – same data stored in different systems • Lack of data control – data are poorly managed • Poor interference – difficult to access data • Delays – There are frequently long delays to requests for data • Lack of reality – Data management systems do not reflect the complexity of the real world • Lack of data integration – data are dispersed across different systems

  5. GIS Database - a collection of interrelated information about geographical objects (e.g, polygons, points, lines, pixels) - stored on some form of mass-storage system (e.g., hard disk, magnetic tape, etc.)

  6. records Student Database - group of related items - related as rows or lines in a database - index field/fields used for ease of extracting info - field/fields used for relating/linking another database file or map fields record 1 record 2 record 3 record 4 record 5 Database structure records fields keys - columns in a database a

  7. Entity or element - an object, event or concept (e.g., house, road, religion) Attribute - property or descriptive characteristics of an entity entityattributes house XY coordinate - location color road line feature Association - links two or more entities (types: many-to-many, many-to-one, one-to-one)

  8. ONE-to-MANY Can have many NATION NATION STOCK Belongs to only one Can have many TC BLDG. ROOMS Belongs only to

  9. MANY-to-MANY Can consist SALE ITEMS Can appear Can have RAINGAUGE RAINFALL DATA Can be found Can consist DIVE OPERATORS RESORT Can be

  10. ONE-to-ONE Belongs to only one BOSS DEPT Has one

  11. Four structures or models of organizing information in GIS * Hierarchical * Network * Relational * Object-oriented

  12. Polygon map Hierarchical data structure Hierarchical - data is organized in a tree structure/tree relationship - structured in one-to-many relations called parent-child/children relation Disadvantages: • system is straightforward -- queries cannot traverse the existing hierarchy • data redundancy -- increases data storage and access costs

  13. Polygon map Network data structure Ring pointer structure for the network representation Network - allows multiple group relations - eliminates data redundancy - useful in navigating around complex topological structures (e.g., polygon networks) Disadvantage: • data storage increases due to overhead of the pointers

  14. Relational - no hierarchy - no pointers - data are stored as a collection of values in the form of sets of records or tuples, grouped together in two - dimensional tables known as relations [each as a separate file] - relational tables are joined through keys - every data field/column can be used as a key - uses Structured Query Language (SQL) method for data manipulation and query - uses normalization method to reduce data redundancy

  15. Relational structure Normalized structure Polygon map Relational structure Normalized structure Relational structure Normalized structure Map = Lines = Polygons =

  16. A “data base/tabular data” example of Normalization of a Relational Data Model:

  17. Relational Advantages: • very flexible -- allow different kinds of data manipulation (search, compare, remove, combine, etc.) • SQL is integrated as a tool in many well-known GIS software Disadvantages: • processing time depends on the complexity between tables being joined • cost

  18. Object-oriented (O-O) - entity is defined in terms of its data records and the logical relations - data in O-O database is defined in terms of a series of unique objects organized into groups of similar phenomena - relationships are established through explicit links

  19. DISTRICT Contains Is situated in TYPE TYPE OWNER SERVICE BUILDING ADDRESS Used by Lives at NAME TYPE AMOUNT CONSUMER USED USER # DISTRICT TYPE SERVICE USER # USER # NAME ADDRESS TYPE CONSUMER AMOUNT USED ADDRESS TYPE BUILDING OWNER TYPE CONSUMER USER # Example of a relational database for utility consumer management Object orientation hierarchy for the same data

  20. Summary Hierarchical approach: useful for dividing spatial data into manageable themes or areas for continuous seamless mapping Network approach: ideal for topologically linked vector lines and polygons Relational approach: ideal for retrieving objects on the basis of their attributes - most flexible ideal for creating new attributes and attribute values from existing data Object-orientation approach: useful when entities share attributes or interact in special ways

  21. Sharing Data files among applications in a DBMS environment Sharing Data files among applications in the file processing environment VS. Application Program 1 Application Program 1 Output 1 Output 1 Data file 1 Data file 1 DBMS Data file 2 Data file 2 Application Program 2 Application Program 2 Data file 3 Output 2 Data file 3 Output 2 Data Base Data Base DataBase Management Systems (DBMS) - set of computer programs for organizing and managing the database to make data quickly available to multitude of users while maintaining its integrity

  22. Structured Query Language (SQL) - English-like, high-level database programming language - makes creating, updating, and manipulating of databases easier - concept is also applied in GIS

  23. 21 4 11 9 Map ID Area (ha) Perimeter (m) Soil Type ID 4 435 880 21 9 210 580 25 11 628 1140 21 21 252 650 15 Soil Type ID Name pH … … 15 Black soil 6.5 21 Brown soil 6.0 25 Red soil 5.0 Example: Storage of GIS attribute information in a relational data base (Author: Qiming Zhou)

  24. Metadata - information or specification of the data - a summary on what data is available on the area of interest, how current, where to acquire, what format, etc. Why is Spatial Metadat Important? • documents existing data holdings and facilitate data sharing • reduces the volume of typically very large spatial data sets to a searchable, while meaningful, size • provides information on the data otherwise not readily available • supports software-based and organizationwide standards • supports easier spatial data access and management

  25. Examples: CVUP Photomosaic Map of Metro Cebu, scale 1:2000 (Courtesy of USC-GIS Center, USC, Cebu City 6000, Phils.)

  26. Quick Look of SPOT Satellite Image of Bantayan Is., Cebu (Courtesy of USC-GIS Center, USC, Cebu City 6000, Phils.

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