Final Test Prep.pptx - What is Where :Whatis where WHAT Characteristics of attributes or features WHERE In geographic space A GIS links attribute and

Final Test Prep.pptx - What is Where :Whatis where WHAT...

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What is Where?
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A GIS can answer the question: What is  where? WHAT: Characteristics of attributes or features. WHERE: In geographic space.
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A GIS links attribute and spatial data Attribute Data Flat File Relations Map Data Point File Line File Area File Topology Theme
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Distinguishing Characteristics of a GIS vs. Other Systems provides links to ATTRIBUTES of points, lines, areas, grids in a database provides algorithms for ANALYSIS of spatial data “spatially intelligent” - “thinks” points, lines, areas, grids are actual spots on earth’s surface - e.g., switching projections, computing distances
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What is a Data Model? A logical construct for the storage and retrieval of information. GIS map data structures are needed for map data models. Attribute data models are needed for the DBMS. The origin of DBMS data models is in computer science.
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A DBMS contains: Data definition language Data dictionary Data-entry module Data update module Report generator Query language
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GIS and DBMS Geographic search is the secret to GIS data retrieval. Many forms of data organization are incapable of geographic search. GI systems have embedded DBMSs, or link to a commercial DBMS. Examples: Dbase, ORACLE, Excel, Paradox
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Database Structures: Flat file Hierarchical Network Relational Object Oriented
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Database structure -Flat file A flat file contains all data in a large table, with rows and columns ID Name Stat e Populatio n Are a Type 1 Whitefish Bay WI 5 Shorewood WI 6 Bayside WI 9 Glendale WI 12 Grafton WI 14 Brown Deer WI 18 Chicago IL 7 records, each record contains 6 fields
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Historically, databases were structured hierarchically in files... USA California Oregon New York Santa Barbara Ventura Contra Costa
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Hierarchical systems Hierarchical systems have a parent/child relation, are easy to understand, update and expand. Direct correlation between one branch and another. Based on formal criteria or key descriptors. Work well if the structure of all possible queries is known beforehand
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Rigid structure Needs lots of index files Creates large files If criterion or key descriptor information is incomplete, search is severely hampered. Hierarchical properties
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Most current GIS DBM is by relational databases. Based on multiple flat files for records Dissimilar attribute structures Connected by a common key attribute. Key is a UNIQUE identifier at the “atomic” level for every record.
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Relational Data Bases Purchase Record Item Date Price  Customer Key Skate Board 2/1/96 49.95 John Smith 42 Baseball Bat 2/1/96 17.99 James Brown 978 Patient Record Key Check-in Check Out Room No.
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  • Cartography, Geographic information system

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