GIS and Mapping Software Introduction

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September 2012 GIS ToT Webinar

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GIS and Mapping Software Introduction

  1. 1. GIS and Mapping Software Introduction
  2. 2. Objective To provide background on GIS and introduce QGIS
  3. 3. Geographic Information System (GIS) is an integration of five basic components GIS is more than just a computer program that produces maps.
  4. 4. Capturing Analyzing Storing DisplayingQuerying Outputting
  5. 5. A GIS combines layers of spatial dataAnswers questions by comparing layers
  6. 6. Querying Data Identify features based on location Identify features based on a conditionAn African country with a population greater than 300,000
  7. 7. GraphsDisplaying DataMaps Tables
  8. 8. Outputting Data
  9. 9. Analyzing Data Proximity Overlay Network
  10. 10. Representing the Natural World in GIS Data
  11. 11. GIS data types – Vector Data• Points • Polygons • water supply wells • Lakes • Village centers • Village areas• Lines • Water lines • Road center
  12. 12. GIS data types – Raster Data• An array of cells• Represents continuous data layer• Best for data without easily defined boundaries• Each cell has one value
  13. 13. Comparison of 2 ways of representing GIS data Vector Raster
  14. 14. Vector Data Vector data provides a complex representation of the world it stores both:  Attributes -- text or numerical information that describe the features (population of a village or number of orphans in a province)  Geometry -- the shape or position of the features (boundary of a country or location of a hospital)
  15. 15. Attributes  Nonspatial information about a geographic feature in a GIS  Stored in a table and linked to the feature by a unique identifier  For example, attributes of a river might include its name, length, and basin. Unique_ID River name Length_km Basin_km2 1 Mississippi 3,730 2,981,076 2 Amazon 6,937 7,050,000 3 Niger 4,180 2,117,700 17
  16. 16. Linking geometry and attributes • Unique identifier links geometry and attributes FID = 60 (Feature Identifier)
  17. 17. Shapefile data format (vector data)  Actually, multiple files  Attributes stored in dBASE table (.dbf file format) Shapefile.dbf table Hospital shapefile “Shape” field Access separate Coordinate file
  18. 18. Topology  The arrangement that constrains how point, line, and polygon features in a vector data file share geometry.  Topology defines and enforces data integrity rules (for example, there should be no gaps between polygons).
  19. 19. Raster Data: Images and grids Rows and columns of equally-sized cells  Each cell stores a value  Detail depends on cell sizeCan be stored in various image file formatsincluding: JPG, IMG, TIF, ASC, BMP, etc
  20. 20. Village-wise Slide Positivity Rate (M alaria) of Trans-Yamuna RegionRasters 2002 2004Images Data based grids Low High
  21. 21. Open Source GIS Software Diva GIS Dev-Info Health Mapper E2G QGIS others?
  22. 22. Open source GIS softwareSoftware NotesQGIS Easy to learn; training materials available; active user community writing modulesDIVA GIS Best suited for point data; limited data classification methods; robust point analysis capabilitiesDev-Info Mainly a data display tool, limited GIS capabilitiesHealth Mapper WHO mapping program; no planned updates; transitioning to DHIS- IIEPI Map Module in Epi-Info; limited GIS capabilities, best suited for Epi-Info users
  23. 23. Key Points GIS is an integration of 5 components GIS represents the world as layers Data can be stored as raster or vector There are standard features that should be present in a GIS:  Storing, Querying, Displaying, Outputting DataAny questions?

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