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What is Where?

What is Where?. Lecture 5 Introduction to GISs Geography 176A Department of Geography, UCSB Summer 06, Session B. WHAT: Characteristics of attributes or features WHERE: In geographic space. You can use a GIS to answer the question: What is where?. What and Where. Depth. Flow.

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What is Where?

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  1. What is Where? Lecture 5 Introduction to GISs Geography 176A Department of Geography, UCSB Summer 06, Session B

  2. WHAT:Characteristics of attributes or features WHERE:In geographic space You can use a GIS to answer the question: What is where?

  3. What and Where

  4. Depth Flow Condition Stream Value Value Value Dam Value Value Value Canal Value Value Value Review: Flat File Database

  5. Arc/node map data structure with files 13 1 x y 11 e 2 x y l i 12 3 x y F 10 2 s 4 x y t 7 n 5 x y i 5 o POLYGON “A” 6 x y P 9 7 x y 4 8 x y 6 1 9 x y 2 10 x y 3 11 x y 8 12 x y 13 x y 1 File of Arcs by Polygon 1,2,3,4,5,6,7 1 A , Area, Attributes : 1,2 1,8,9,10,11,12,13,7 2 Arcs File

  6. Attribute Data Flat File Relations Map Data Point File Line File Area File Topology Theme A GIS links attribute and spatial data

  7. A logical construct for the storage and retrieval of information. GIS map data structures are map data models. Attribute data models are needed for the DBMS. The origin of DBMS data models is in computer science. What is a Data Model?

  8. Data definition language Data dictionary Data-entry module Data update module Report generator Query language A DBMS contains:

  9. Ability of the DBMS or GIS to get back on demand data that were previously stored Geographic search is the secret to GIS data retrieval. Many forms of data organization are incapable of geographic search GISystems have embedded DBMSs, or link to a commercial DBMS Examples: Access, Dbase, ORACLE, Excel, Paradox GIS and DBMS

  10. Historically, databases were structured hierarchically in files...

  11. Based on multiple flat files for records Dissimilar attribute structures Connected by a common key attribute. Key is a UNIQUEidentifier at the “atomic” level for every record. Most current GIS data management is in relational databases

  12. Relational Data Bases

  13. Searches by attribute: find and browse. Data reorganization: select, renumber, and sort. Compute allows the creation of new attributes based on calculated values. Retrieval Operations

  14. sort renumber subset search DBMS queries via the query language

  15. Command line attribute query find in states where state_name = ‘California’ <1 record in result> use states calculate in states population_density = population / area <50 records in result> restrict in states where population_density > 1000 <20 records selected in result>

  16. GIS query is usually by command line, batch, menu or macro. Most GIS packages use the GUI of the computer’s operating system to support both a menu-type query interface and a macro or programming language. SQL is a standard interface to relational databases and is supported by many GISs. The Retrieval User Interface

  17. Attribute queries are not very useful for geographic search. In a map database the records are features or themes The spatial equivalent of a find is locate, the GIS highlights the result. Spatial equivalents of the DBMS queries result in locating sets of features or building new GIS layers. Spatial Retrieval Operations

  18. Buffering is a spatial retrieval around points, lines, or areas based on distance. Overlay is a spatial retrieval operation that is equivalent to an attribute join. Spatial Search

  19. Identify

  20. Recode OR

  21. Data overlay

  22. Overlay 0 1

  23. And Or Max Min Exhaustive set Types of overlay operations

  24. Buffer

  25. Combinations of spatial and attribute queries can build some complex and powerful GIS operations, such as weighting. Weighted overlay analysis really just complex retrieval. Complex Retrieval: Map Algebra

  26. Weights of Evidence Analysis Of Maya Settlement locations, Belize River, Belize Weighted Overlay Analysis

  27. Topographic Slope (in percent)

  28. Soil drainage property

  29. Soil fertility

  30. Distance to streams

  31. WofE Model 1

  32. WofeE Model 2

  33. Model explains 75% of settlement locations Eliminated lakes, Strahler order, Belize river as contributory factors Streams important up to 400m Validation with GPS field data Extending model to regional data Results

  34. Unsurveyed sites added by GPS

  35. Why is there? Coming next….

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