Geographical information and GIS advantages

Geographical information has two parts:

• Spatial data, tied to a location, in the form of points (a well), lines (a road) or areas (a district);
• Non-spatial (attribute) data: facts about those features, like a road's width.

Example: a list of the parts in a cycle shop's stock is non-spatial; the literacy rate of each state is spatial, because it is tied to places on a map.

Spatial data come from data suppliers, from digitising existing maps, or from one's own surveys.

A paper map shows information in a fixed way, with a scale, symbols, colours and a coordinate system; changing it means redrawing it. GIS stores the data separately from how they are presented, so we can:

• query the data and map the answers;
• overlay layers to create new information;
• create buffers around features;
• link different data sets by location.