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What is Where?

What is Where?. Getting Started With Geographic Information Systems Chapter 5. You can use a GIS to answer the question: What is where?. WHAT: Characteristics of attributes or features WHERE: In geographic space. What and Where. Stream. Value. Value. Value. Dam. Value. Value. Value.

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What is Where?

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  1. What is Where? Getting Started With Geographic Information Systems Chapter 5

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

  3. What and Where

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

  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 Figure 3.4 Arc/Node Map Data Structure with Files.

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

  7. What is a Data Model? 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.

  8. Data Models and Memory

  9. Data Base Management SystemsWhich is Spatial? • A. ORACLE • B. INFORMIX • C. ACCESS • D. MySQL • E. Paradox

  10. Some Non-spatial DBMSs • Microsoft Visual FoxPro • MySQL • PostgreSQL • Progress • SQLite • Teradata • CSQL • OpenLink Virtuoso • Oracle database • IBM DB2 • FileMaker • Firebird • Ingres • Informix • Microsoft Access • Microsoft SQL Server

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

  12. GIS and DBMS 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 GI systems have embedded DBMSs, or link to a commercial DBMS Examples: Access, Dbase, ORACLE, Excel, Paradox

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

  14. Most current GIS data management is in relational databases 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.

  15. Relational Data Bases

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

  17. The Retrieval User Interface 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.

  18. SQL examples UPDATE customers SET salesperson = "Mike" WHERE state = "NH" SELECT customers.* FROM customers WHERE customers.customer_id NOT IN(SELECT customer_id FROM orders WHERE year(orders.order_date) = 2004)

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

  20. Subset: Select

  21. Spatial Retrieval Operations 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.

  22. Data dictionary

  23. Select by rectangle

  24. Search for a city

  25. Select where cities = capital

  26. Sort (by population)

  27. Spatial Search 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.

  28. Identify

  29. Recode OR

  30. Data overlay

  31. Overlay 0 1

  32. Overlay

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

  34. Buffer

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

  36. Tomlins’s Spatial Operations Focal Zonal Global

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

  38. Topographic Slope (in percent)

  39. Soil drainage property

  40. Soil fertility

  41. Distance to streams

  42. WofE Model 1

  43. WofeE Model 2

  44. Results • Model explains 82% of settlement locations+, 100%- • Eliminated lakes, Strahler order, Belize river as contributory factors • Streams important only 400-1000m • Validation with GPS field data • Extending model to regional data

  45. Detail

  46. Unsurveyed sites added by GPS

  47. Coming next…Why is it there?

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