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  1. 1. Fundamental GIS Database Concepts Contents The GIS Database Graphic Data Symbology Annotation Layers Nongraphic Data Topology Data Management Basic Data Models Tables SQL Data Directory Database Administration Distributed GIS Summary References The GIS Database Definitions  Database – an integrated set of data on a particular subject  Geographic (=spatial) database - database containing geographic data of a particular subject for a particular area  Database Management System (DBMS) – software to create, maintain and access databases
  2. 2. Advantages of Databases over Files  Avoids redundancy and duplication  Reduces data maintenance costs  Applications are separated from the data  Applications persist over time  Support multiple concurrent applications  Better data sharing  Security and standards can be defined and enforce Disadvantages of Databases over Files  Expense  Complexity  Performance – especially complex data types  Integration with other systems can be difficult
  3. 3. Characteristics of DBMS (from Longley)  Data model support for multiple data types  e.g MS Access: Text, Memo, Number, Date/Time, Currency, AutoNumber, Yes/No, OLE Object, Hyperlink, Lookup Wizard  Load data from files, databases and other applications  Index for rapid retrieval  Query language – SQL  Security – controlled access to data  Multi-level groups  Controlled update using a transaction manager  Backup and recovery  DBA tools  Configuration, tuning  Applications  CASE tools  Forms builder  Reportwriter  Internet Application Server  Programmable API Back to top
  4. 4. A GIS database can be divided into two basic types of data: graphic and nongraphic. Each of these types has specific characteristics, and each as different requirements for efficient data storage, processing and display. Graphic Data  Graphic data are digital descriptions of map features. They may include the coordinates, rules, and symbols that define specific cartographic elements on a map.  The GIS uses graphic data to generate a map or cartographic picture on a display, paper, or other media 6 Types of Graphic Elements 1. Points  Zero-dimensional object that specifies a geometric location through a set of coordinates. A node is a special type of point that is a topological junction or end point and may specify a geometric location. 2. Lines  A line is a one-dimensional object. A line segment is a direct line between two points. Special forms of lines include strings, arcs, and chains. 3. Areas  Are bounded, continuous two-dimensional objects that may or may not include its boundary. Individual areas are represented as polygons.
  5. 5. Image -Copyright © 2000, Urban and Regional Information Systems Association 4. Grid cells Are two-dimensional objects that represent a single element of a continuous surface. Raster point data is represented by a single cell. Line data is represented by a series of neighboring cells and areas by groups of contiguous cells. Grid Cell 5. Pixels A two-dimensional picture element that is the smallest indivisible element of an image Pixel . 6. Symbols  Graphic elements that represent features at points on a map  Abstract geometric shapes can be used to represent real world features  Computer graphics have facilitated the use of more complex and meaningful symbols
  6. 6. Building Road Tree jle l x q hybdqnkytrxpw h GIS is equipped to display a wide variety of symbols for points, lines, and areas. Symbols are frequently constructed and stored in system libraries, reflecting traditional cartographic representations or custom graphics Check out the site on-line, created by users of ESRI products. The site is a resource for more symbol sets, downloadable for free. The Unofficial Arc/Info and ArcView Symbol Page  This is a point symbol palette from ArcView  ArcView also provides extensive line symbols to represent linear features such as rivers, roads, and railroads.
  7. 7. Back to top Annotation The text or labels plotted graphically on a map and includes such items as street names, place names, identification numbers, and dimensions.  Usually not stored like other map features in GIS. It is not stored as strings of coordinates but often rather as a combination of location coordinates, standard fonts, and placement or orientation rules.  Three other items of information are stored for annotation  Location Sample Fonts  Orientation Times Roman  Size  Annotation is the alphanumeric text or labeling placed on maps. Cursive Carlson Arial Black Back to top Book Antiqua Castellar Garamond Layers
  8. 8.  The graphic component of the GIS database is often described as a series of layers, each of which contains map features that are related functionally.  Each layer is a set of homogeneous features that is registered positionally to the other data base layers through the common coordinate system.  The electronic layering scheme is comparable to a series of overlays in a manual mapping system.  The sequence of layers usually begins with the reference grid or base features.  The concept of data organization in layers is useful for communicating data structure Image -Copyright © 2000, Urban and Regional Information Systems Association
  9. 9. Back to top Nongraphic Data  Nongraphic data are representations of the characteristics, qualities, or relationships of map features and geographic locations  They are stored in standard alphanumeric format  Often called textual data or attributes  They are related to geographic locations or graphic elements and are linked to them in the GIS through common identifiers or other mechanisms.  Provide descriptive information about the characteristics of map features. Four Classes of Nongraphic Data 1. Nongraphic Attributes  Describe in words and numerals the entities represented by the graphic elements  Can include qualitative and quantitative data that describe a point, line, polygon, or network feature stored in the database.  A GIS is able to query or analyze the attributes separately and to generate a map based on nongraphic values, for example, all sites with gold crowns in them.  Describe the map features  Linked to graphic elements through identifiers or geocodes 2. Geographically Referenced Data  Describe physical phenomena, human-made features, and events that occur at a specific geographic location  Stored and managed in separate files and systems that are not directly associated with the graphic features in a GIS database.  They do contain elements that identify the location of the event of phenomenon. Building permits through street addresses, for example.  Describe items or actions at a geographic location.  They DO NOT describe the map feature
  10. 10.  Examples: building permits, accident reports, health inspections 3. Geographic Indexes  Help locate map features and data based on their geographic identifiers  An index may include multiple identifiers for entities used by different organizations as well as listings of geocodes that identify the spatial relationships between locations or between features and geographic entities.  Used to locate rows quickly  RDBMS use simple 1-d indexing (R-tree, B-tree, etc.)  Spatial DBMS need 2-d, hierarchical indexing
  11. 11.  Grid  Quadtree  R-tree  Others  Multi-level queries often used for performance (MBR)  Used to select, relate, and retrieve spatial data  Example: street address, mailing address, parcel number, account number 4. Spatial Relationships  Descri S P A T IA L ptions of the R E L A T IO N S H IP S 1 2 C o n n e c tiv ity A d ja c e n c y P r o x im ity proximity, adjacency, and connectivity of map features  Where things are located in proximity to each other  Some relationships also can be interpreted or calculated form the geographic coordinates of graphic elements- for example, number of arch sites within a five-mile radius of a natural spring.  Topological relationships  example: nodes terminated at a specific link  example: interpreted or calculated relationships Back to top
  12. 12. Topology The relative location of geographic phenomena independent of their exact position. In digital data, topological relationships such as connectivity, adjacency and relative position are usually expressed as relationships between nodes, links and polygons. For example, the topology of a line includes its from- and to-nodes, and its left and right polygons. Topology is useful in GIS because many spatial modeling operations don't require co- ordinates, only topological information. For example, to find an optimal path between two points requires a list of the lines or arcs that connect to each other and the cost to traverse each line in each direction. Co-ordinates are only needed for drawing the path after it is calculated. (Copyright © 1999, Association for Geographic Information)  Topology a technique used to record and manipulate the logical relationships of map features and geologic information in a GIS  Used in editing and quality control and retrieval and analytical functions ArcUser Article on Topology and Shapefiles Back to top Data Management  Since the storage structures can be tailored to the characteristics of the various data types, a GIS could have a graphic structure for coordinates, a topological structure for spatial relationships, and a conventional data base management system for attributes.  Graphic data - high volume, requires efficient find and retrieval procedures
  13. 13.  Non graphic data generally can use standard alphanumeric data management software and structures Back to top Basic Data Models Hierarchical  parent-child relationships  one-to-many relationships  efficient for “standard” or predefined queries  “Computer database structures employing parent child or one- to-many relationship that requires direct linkages among items for a search to be successful” (2005 DeMers). Sequential or Flat File  Not a true database management system  Files managed by specifically developed systems or programs in COBAL, BASIC or other languages
  14. 14.  Tailored to individual applications  Ordered based on some form of alphanumeric scheme much more like alphabetizing a mailing list. This file structure makes it more difficult for data input, but allows searches and retrieval with greater speed than with simple lists. Relational  Based on matrix structure of rows and columns of data   Facilitates ad-hoc queries  Assumes non-standard inquiries  Most popular choice for GIS  “Big” vendors include: Oracle, Sybase, Ingres, Microsoft Access  Data stored as tuples (tup-el), conceptualized as tables  Table – data about a class of objects  Two-dimensional list (array)  Rows = objects  Columns = object states (properties, attributes)  Most popular type of DBMS  Over 95% of data in DBMS is in RDBMS  Commercial systems  IBM DB2  Informix  Microsoft Access  Microsoft SQL Server  Oracle  Sybase  “Computer database structures employing an ordered set of attribute values or records known as tuples grouped into two-dimensional tables called relations” (2005 DeMers).
  15. 15. Object-Oriented  Object-oriented – OODBMS “GIS systems based on object-oriented programming methods and demonstrating object inheritance” (2005 DeMers). Network  Can model one-to many or many-to-many relationships  Records of the same type are grouped into conceptual files  Unlike hierarchical data structures, network systems are not restricted to paths up and down hierarchical pathways  “Computer database structures employing a series of software pointers from one data item to another. Unlike hierarchical data structures, network systems are not restricted to paths up and down hierarchical pathways” (2005 DeMers). Back to top Tables A table lets you work with data from a tabular data source in ArcGIS. You can bring data from almost any tabular data source in your organization into ArcGIS as tables. Then you can add data from these tables to maps, and symbolize, query and analyze this data geographically.  Table – data about a class of objects  Two-dimensional list (array)  Rows = objects  Columns = object states (properties, attributes)
  16. 16. Column = property Row = object Table = Object Class Object Classes with Geometry called Feature Classes Sources of Tabular Data in ArcView  dbase, INFO, and delimited text files  SQL database servers  From ArcMap, you can connect to a database server, such as Oracle or Sybase, and run an SQL to retrieve records from it as a table. ArcMap stores the definition of the SQL query you used, not the records themselves. See Connecting to a database to create a table Back to top SQL  Structured (Standard) Query Language – (pronounced SEQUEL)
  17. 17.  Developed by IBM in 1970s  Now de facto and de jure standard for accessing relational databases  Three types of usage • Stand alone queries • High level programming • Embedded in other applications Types of SQL Statements  Data Definition Language (DDL) • Create, alter and delete data • CREATE TABLE, CREATE INDEX  Data Manipulation Language (DML) • Retrieve and manipulate data • SELECT, UPDATE, DELETE, INSERT  Data Control Languages (DCL) • Control security of data • GRANT, CREATE USER, DROP USER Back to top Data Directory  a.k.a. Database Design or Database Dictionary  A data dictionary is essential to effective management of database. It defines entities, attributes and valid values.  The data dictionary also includes information that describes accuracy, completeness, vintage, or other data characteristics. Review this example of a data dictionary: Data Dictionary Back to top
  18. 18. Database Administration  Protect database integrity  Maintain data directory or database design  Control passwords and access to database  Establish data standards, definitions, quality, and maintenance schedules  Backup and copy data Back to top Distributed GIS  Maintain data directory or database design  Control passwords and access to database  Establish data standards, definitions, quality, and maintenance schedules T  The component parts can be at different locations  The user  The data  The software  The network links all of the parts together The Subject Location  Also important to GIS is the area that is the subject of the GIS project  In principle a subject area can be studied by a GIS user located anywhere on the Earth's surface  The power of GIS is greatly enhanced when the user is located in the subject location  Information from the database can then be combined with information from the user's senses The Role of Standards  Distributed GIS relies on the adoption of common standards  To allow the various components to operate together  Such standards have been developed by various national and international bodies, aided by the Open Geospatial Consortium
  19. 19. Distributing the Data  It must be possible to find remotely located data  Data documentation, or metadata, provides the key to successful search  The U.S. Federal Geographic Data Committee devised a much-emulated standard for geographic data description  The Content Standard for Digital Geospatial Metadata Geolibraries and Geoportals  A Geolibrary is a digital library containing georeferenced information  Its search mechanism uses geographic location as the primary key www.alexandria.ucsb.edu  A Geoportal is a digital library of geographic data and GIServices  A one-stop shop for information relevant to GIS www.geo-one-stop.gov The Mobile User  It is increasingly possible to obtain the services of a GIS through hand-held and wearable devices  Some cell phones can now be used to generate maps  Such maps can be centered on the user's current location http://www.garmin.com/pressroom/corporate/090805.html
  20. 20. Virtual Reality  Use of digital technology to create an artificial visual and auditory environment that simulates the actual environment elsewhere  User and subject are in different locations  Technology allows the user to explore a remote location www.casa.ucl.ac.uk/research/virtuallondon.htm and www.cvrlab.org Augmented Reality  The user is in the subject location  Technology is used to augment the user's senses  Information from a database can be displayed directly in the user's field of view  Superimposed on what is actually seen Distributing the Software  A GIService is a GIS process provided remotely  A user can send a request and receive a result  A gazetteer service will accept a placename and return that location's coordinates  A geocoding service will accept a street address and return the house's coordinates Advantages of GIServices  Users do not need to obtain and install expensive software  Only one version of the service software need exist  It is always the latest version  Data used in the service can be kept constantly up to date Back to top
  21. 21. Summary  Database – an integrated set of data on a particular subject  Databases offer many advantages over files  Relational databases dominate  Some limitations for GIS Back to top References  Antenucci, John et. Al. Geographic Information Systems - A Guide to the Technology. New York: Van Nostrand Reinhold, 1991. Chapter 5: DataBase Concepts pp. 96-102.  DeMers, M N. Fundamentals of Geographic Information Systems. (2005) John Wiley and Sons Ltd.  Geographical Information Systems and Science. Longley PA, Goodchild MF, Maguire DJ, Rhind DW. (2001) John Wiley and Sons Ltd.  Tutorial on GIS Database Concepts, A Free On-Line Publication Of Urban and Regional Information Systems Association, Prepared with the support of PlanGraphics, Inc.  Foote, K. The Geographer's Craft, Department of Geography, University of Texas at Austin.  Many of the sections in this web page were modified from the instructors slides developed for the Longley text.