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Lecture 4

Lecture 4. Data. Why GIS?. Ask questions Solve a problem Support a decision Make Maps Involve others, share data, procedures, ideas. What is a GIS?. GISs are simultaneously the telescope, the microscope, the computer, and the Xerox machine of regional analysis and synthesis

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Lecture 4

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  1. Lecture 4 Data

  2. Why GIS? • Ask questions • Solve a problem • Support a decision • Make Maps • Involve others, share data, procedures, ideas

  3. What is a GIS? GISs are simultaneously the telescope, the microscope, the computer, and the Xerox machine of regional analysis and synthesis of spatialdata.(Ron Abler, 1988)

  4. Definition 1: A GIS is a toolbox "a powerful set of tools for storing and retrieving at will, transforming and displaying spatialdata from the real world for a particular set of purposes" (Burrough, 1986, p. 6). "automated systems for the capture, storage, retrieval, analysis, and display of spatialdata." (Clarke, 1995, p. 13).

  5. Definition 2: A GIS is an information system "An information system that is designed to work with data referenced by spatial or geographic coordinates. In other words, a GIS is both a database system with specific capabilities for spatially-referenced data, as well as a set of operations for working with the data" (Star and Estes, 1990, p. 2).

  6. Definition 3: GIS is an approach to science • Geographic Information Science is research both on and with GIS. "the generic issues that surround the use of GIS technology, impede its successful implementation, or emerge from an understanding of its potential capabilities." (Goodchild, 1992)

  7. Definition 4: GIS plays a role in society Nick Chrisman (1999) “organized activity by which people measure and represent geographic phenomena, and then transform these representations into other forms while interacting with social structures.”

  8. Components of a GIS • Hardware • Software • Procedures • People with skills to complete tasks • Data

  9. Hardware • Computer, CPU, memory, and monitor • Modem and internet connection • Data collection devices, GPS, handheld data • Scanner or digitizing table • Plotter and printer • Web Server

  10. Software • GIS software – range of functions • Software extensions – add functions • Data viewers – least functionality • Single purpose software – make parcel maps • Software for the web – ATM, House locators • Non-GIS software - database, statistics, image processing

  11. Procedures • Data input – paper maps, GPS, images • Data management - edit and quality • Query - Asking map questions • Analysis - Spatial, tabular and statistical analysis • Map overlay • Distance calculations • Data output - Map making, on screen, paper, internet

  12. People with spatial knowledge • Data entry • Data quality • Analyst • Developer / Programmer • Database manager • Web developer • Project manager • GIS manager www.gjc.org - GIS jobs listing

  13. Data types • Maps and Layers • Vector • Raster • TIN • 3D • Text • Metadata

  14. Data storage formats • Maps and layers • Mxd • lyr • Vector • Geodatabase, shapefile, coverage • DXF, DWG DGN • Raster • GRID, sid, img, gif, jpeg • Tables • Geodatabase, dbf, • 3D • TIN format

  15. Polygons Lines Points 4753456 623412 4753436 623424 4753462 623478 4753432 623482 4753405 623429 4753401 623508 4753462 623555 4753398 623634 Vector data • Point - x, y • Line - list of x, y coordinates • Polygon - list of lines that form a closed area

  16. Vector layers

  17. Feature class • Group of points, lines, or polygons • Has a theme-rivers, streets, cities, lakes, states… • Makes a layer Polygon feature class Point feature class Line feature class

  18. Shapefile • Three files, .shp, (.dbf, .shx) • Files contain either points, lines, or polygons

  19. Layer files • File for one layer, stores its symbology • .lyr extension, streets.lyr • Add to any map or share with friends • No data • Pointer to data • Symbols

  20. Geodatabase • One file - Access format .mdb file • Point, line, & polygon feature classes • Tables too

  21. What is a database • Storage format • Container for tables of data • Allows queries • The sales table contains five tables

  22. Table structure • Fields • Rows • Cells

  23. A feature class table • Has a geometry field • You can’t see the actual values, too big

  24. Field menu • Sort

  25. Options menu

  26. Select By Attributes

  27. Build a SQL expression • Field, Operator, Value to search for

  28. Records get selected • Pop90_SQMI < 30

  29. Features get selected too • Pop90_SQMI < 30

  30. Make table steps • Get or make a database • Make a table • Add fields • Add records • Add values

  31. Make a personal geodatabase

  32. A .mdb file is Microsoft Access format

  33. Make a new table in the database

  34. Name it and default configuration

  35. Add fields, type in name and type

  36. Data Types and Length

  37. Drag the table to ArcMap for editing

  38. Add Editor toolbar, Start editing

  39. Empty table to start, start typing

  40. Type a value into a cell

  41. Type in all values

  42. Stop editing, save edits

  43. Turn off Editor toolbar

  44. Make a Geodatabase exercise • Make an access database • Convert a shapefile • Build relationships with other tables • Add fields • Calculate fields • Join fields

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