1. A planning system for scheduling the operation of autonomous entities within a defined geographical region, the planning system operating at three hierarchical levels: a) a region plan level in which processing is undertaken in respect of planning operations at a strategic level across the geographical region, b) an operation plan level in which processing is undertaken in respect of entity-related operations to be performed by autonomous entities in selected localised zones of the geographical region having operation-defined geographical boundaries, and c) a task plan level in which processing is undertaken in respect of specific tasks to be performed by said autonomous entities, in undertaking the operations wherein the operation of the planning system comprises generating control information defining activities at the region plan level, the operation plan level and the task plan level and making the control information available to the autonomous entities for implementation.