Layer based GIS :

1) This approach is the most widely used. The layering approach allows users to visualise a map database as a set of registered map separations.

2)This layered approach is illustrated in Fig. Each layer is thematic and reflects either a particular use or a characteristic of the land use.

For example, layer one describes land use characteristic and layer two, soils.

3) The layered approach to structuring spatial information characterised by the use of thematic maps may be derived from the analysis of remote sensing data to show different features of the area.

4) The concept of breaking the real world into a series of thematic layers is the process that is used to develop the first map overlay analysis .

5) The logical extension of the layer concept is the use of tiles. This approach breaks down geographical space into a series of regular or irregular units that can be reassembled through the use of a coordinate system.

In this model, GIS requires that data are broken down into a set of logical terrain units to assist with physical display of data.

Feature based GIS : This is a new approach having the trappings of

object oriented GIS, spatial analysis functionality from raster models and power from vector models.