Nile Basin Decision Support System

A Geographic information system (GIS) is a computer system designed to capture, store, manipulate, analyze, manage, and present all types of spatial or geographical data. GIS applications are tools that allow users to create interactive queries, analyze spatial information, edit data in maps, and present the results of all these operations.

What are the uses of GIS?

GIS has many applications in various fields today. Some of which include traditional geographically related fields like urban planning and cartography, but also environmental impact assessment reports and natural resource (e.g. water, land) management.

In addition, GIS is now finding its place in business and related fields. Business GIS as it has come to be known is usually the most effective in advertising and marketing, sales, and the logistics of where to locate a business.

 Whichever way it's used though, GIS has had a profound influence on geography and will continue to be used in the future as it allows people to efficiently answer questions and solve problems by looking at easily understood and shared data in the form of tables, charts, and most importantly, maps.

What are the main GIS data formats?

There are two main data formats for storing GIS data. These are the vector and the raster format. The vector format has three basic objects in the its data model: points, lines, and polygons. These are defined by the coordinates of the point or the coordinates of the vertices of the line or polygon. The vector data model is often the data model of choice for GIS because it can contain information about topology which underlies a large number of GIS operations. The raster format is used in a GIS application when we want to display information that is continuous across an area and cannot easily be divided into vector features such ground levels. A raster dataset is composed of rows (running across) and columns (running down) of pixels (also known as cells). Each pixel represents a geographical region, and the value in that pixel represents some characteristic of that region. A Temporal Raster is used to represent a time series of rasters (e.g. satellite rainfall maps at different times) which share the same extents and projection.

What are GIS projections?

Projections are a mathematical transformation that take spherical coordinates (latitude and longitude) and transform them to an XY (planar) coordinate system. This enables you to create a map that accurately shows distances, areas, or directions. With this information, you can accurately work with GIS data to calculate areas and distances and measure directions.