Turning is the process of going from one arc segment to the adjacent arc segment through the middle node. The turn cost is the cost required to complete the turn. The steering table is used to store the steering cost value. The turning table must list all possible turns at each intersection, which generally includes four fields: Start Edge Field (FromEdgeID), End Edge Field (ToEdgeID), Node ID Field (NodeID) and Turn Cost Field (TurnCost). These fields are associated with the fields in the arc and the node, and each record in the table represents the arc cost required for a way to pass through the intersection. The turn cost is usually directional, and when the turn is prohibited, the turn cost value is -1.
Note: The cost unit depends on the actual cost content. If the cost field represents the time cost, then the cost field unit is the time unit, such as hours, minutes, seconds, etc.; if the cost field represents the distance cost, then the cost field unit is the Distance unit, such as meters, kilometers, feet, etc.
