Contours from Autocad drawing as dxf [create TIN] TIN1
 

Discussion :

• The data model(s) created allows a successful combination of information in three dimensions stored in two layers i.e. the Hydrology layer shows the plan view and the DEM has elevation information. So in effect we are processing information in three dimensions.
• The Buffers created using the raster database are more detailed than those created with vector data. Each cell in the buffer area has a value which helps to indicate itsdistance from the water and consequently its importance in the preservation strategy, whereas a vector polygon is undifferentiated.
• The model uses "combine" to create various classes of streams based on slope and store the information on one layer.  "Merge" allows the simple addition of data from two layers (lakes and flat streams) into one layer.
• Even though each cell is a unit, "clump" allows us to create entities by grouping selected cells.
• The cell size restricts the accurate representation of line entities like streams and canals. Minimum width of the stream represented has a least count equal to the cell size. This results in increased area of streams and canals.
• Rasters allow us to work at a chosen or appropriate level of complexity. Theoretically each cell can have a unique value, but we can group these into selected categories reducing the level of detail.