Introduction
Location Map
Base Map
Database Schema
Conventions
GIS Analyses
Flowchart
GIS Concepts
Results
Conclusion
References

GIS CONCEPTS

Raster Data:

Raster data are one of the available data formats utilized in GIS.  A raster is a matrix of cells (can be thought of as pixels) organized into rows and columns where each cell contains a spatial location and a value representing some type of information, such as land- cover type.  Raster data can be thematic- representing discrete features, or continuous- representing a feature that is continuous, though varying spatially.

For example:

(From ESRI.com)

Clip Analysis Tool:

The clip analysis tool is available in the ArcGis toolbox.  It is used to limit the extent of a layer to the boundary of another layer.   Essentially, it allows you to cut out a piece of one layer using the features of another layer.  Thus, a new layer can be created that contains a geographic subset identical to another smaller layer.

In our case, we began with a raster dataset that included the entire globe.  We were only interested in the data for Ethiopia, so we used a layer that contained the boundary of Ethiopia.  We then clipped the global climate data to the Ethiopian border, and created a new layer of Ethiopian climate data.  Although our project used raster data, line and point data can also be transformed and clipped with this tool.

(From ESRI.com)

Raster Calculator:

The Raster Calculator is a versatile and robust tool that performs “Map Algebra” on the raster dataset. Since each pixel is a discrete entity with a particular value, it is possible to utilize mathematical calculations and functions.  Similarly, the raster calculator is a method of querying data or identifying specific features, detecting subtle differences between time-series, or any number of possible other applications.