
6 Computing in Geographic Information Systems
FIGURE 1.1
Block diagram depicting the macro GIS functions
As an example, computing the shortest path between start location and
destination location, the computing steps can be performed through the fol-
lowing series of algorithms:
Input = {Source Location, Destination Location, Vector Topo Sheet with
Communication Layers, Digital Elevation Model Corresponding to the Topo
Sheet, Weather Information, Attribute Data}
• Step 1: Read the vector data and extract the communication Layer from
it.
• Step 2: Generate a DAG (Directed Acyclic Graph) from the communication
layer.
• Step 3: Store the DAG in a 2D array