September 2012 GIS ToT Webinar

1. GIS and Mapping Software
Introduction

2. Objective
 To provide background on GIS and introduce
QGIS

3. Geographic Information System (GIS) is an integration
of five basic components
GIS is more than just a computer program that produces maps.

4. Capturing Analyzing
Storing Displaying
Querying Outputting

5. A GIS combines layers of spatial data
Answers questions by comparing layers

6. Querying Data
Identify features based on location
Identify features based on a condition
An African country with a population greater than 300,000

7. Graphs
Displaying Data
Maps
Tables

8. Outputting Data

9. Analyzing Data
Proximity
Overlay
Network

10. Representing the Natural World in GIS Data

11. GIS data types – Vector Data
• Points • Polygons
• water supply wells • Lakes
• Village centers • Village areas
• Lines
• Water lines
• Road center

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. Comparison of 2 ways of representing GIS data
Vector
Raster

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. 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. Linking geometry and attributes
• Unique identifier links geometry and attributes
FID = 60
(Feature Identifier)

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. 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. Raster Data: Images and grids
 Rows and columns of equally-sized cells
 Each cell stores a value
 Detail depends on cell size
Can be stored in various image file formats
including: JPG, IMG, TIF, ASC, BMP, etc

20. Village-wise Slide Positivity Rate (M alaria) of Trans-Yamuna Region
Rasters 2002 2004
Images Data based grids
Low High

21. Open Source GIS Software
 Diva GIS
 Dev-Info
 Health Mapper
 E2G
 QGIS
 others?

22. Open source GIS software
Software Notes
QGIS Easy to learn; training materials available; active
user community writing modules
DIVA GIS Best suited for point data; limited data
classification methods; robust point analysis
capabilities
Dev-Info Mainly a data display tool, limited GIS
capabilities
Health Mapper WHO mapping program; no planned updates;
transitioning to DHIS- II
EPI Map Module in Epi-Info; limited GIS capabilities, best
suited for Epi-Info users

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 Data
Any questions?