Once you have a functioning GIS containing your geographic information, you can begin to ask questions such as:

• Where are all the sites suitable for building new houses?
• What is the dominant soil type for oak forest?
• If I build a new highway here how will traffic be affected?

Both simple and sophisticated queries utilizing more than one data layer can provide timely information to analysts and managers alike.

GIS systems really come into their own when they are used to analyze geographic data. The processes of geographic analysis (often called spatial analysis or geoprocessing) uses the geographic properties of features to look for patterns and trends, and to undertake "what if" scenarios. Modern GISs have many powerful analytical tools, but two are especially important. Proximity Analysis

• How many houses lie within 100 m of this water main?
• What is the total number of customers within 10 km of this store?
• What proportion of the citrus crop is within 500 m of the well?

The integration of different data layers involves a process called overlay. At its simplest, this could be a visual operation, but analytical operations require one or more data layers to be joined physically. This overlay, or spatial join, can integrate data on soils, slope, and vegetation, or land ownership with tax assessment.