Geographical Information System (GIS) is a powerful computer-aided database management and mapping technology that uses for organizing and storing large amount of multi-purpose information. GIS provides an interface between the data and a map. For example by using GIS maps we can show visually the trends of disease or injuries in a particular geographical region, GIS gives us the power for modeling trends in the future.

WHO suggests the following options as examples of using GIS in Public Health:

• Determining geographic distribution of diseases
• Analyzing spatial and temporal trends
• Mapping populations at risk
• Stratifying risk factors
• Assessing resource allocation
• Planning and targeting interventions
• Monitoring diseases and interventions over time

If you wish to learn GIS and you do have no access to the software, you can buy the book: Getting to know ArcGIS (today the online price is around $ 35), the book includes a trial copy of ArcGIS desktop software (Arc GIS 9.2) for 6 months using for free, so you have enough time to get familiar and learn the software.If you go online you can find a tremendous amount of resources for learning GIS, one of the online resources that I like is Yale University Map Collection. Yale provides a lot of tutorials and data for practice (for free).If you take a GIS course and your teacher asks you to do a project and you need an easy to use data in different subjects you can go to Michigan Geographical Data Library, for conducting any kind of projects in GIS course including Raster data, Michigan site is a fabulus place to look. Good Luck