A method for passively detecting aircraft wingtip strikes, comprising the steps of: in a processing system: generating a digital base map of at least a portion of an aerodrome that includes one or more specific wingtip strike threats, the digital base map represented by a plurality of aerodrome cells; generating a digital aircraft structure representative of an aircraft, the digital aircraft structure represented by a plurality of aircraft cells; characterised by: assigning a numeric value to each of the aerodrome cells, the numeric value assigned to each aerodrome cell representative of the specific wingtip strike threat, associated with that aerodrome cell; generating an index count array, the index count array having a separate entry for each numeric value; determining whether a portion of the aerodrome cells are or would be replaced with the plurality of aircraft cells; counting each numeric value of the aerodrome cells that are or would be replaced to determine a replacement count associated therewith; entering the replacement count associated with each numeric value into the separate entry in the index count array for that numeric value; detecting one or more potential aircraft wingtip strikes based on the replacement counts in the index count array, wherein the digital aircraft structure comprises a plurality of protective envelopes around the aircraft. in a processing system: generating a digital base map of at least a portion of an aerodrome that includes one or more specific wingtip strike threats, the digital base map represented by a plurality of aerodrome cells; generating a digital aircraft structure representative of an aircraft, the digital aircraft structure represented by a plurality of aircraft cells; characterised by: assigning a numeric value to each of the aerodrome cells, the numeric value assigned to each aerodrome cell representative of the specific wingtip strike threat, associated with that aerodrome cell; generating an index count array, the index count array having a separate entry for each numeric value; determining whether a portion of the aerodrome cells are or would be replaced with the plurality of aircraft cells; counting each numeric value of the aerodrome cells that are or would be replaced to determine a replacement count associated therewith; entering the replacement count associated with each numeric value into the separate entry in the index count array for that numeric value; detecting one or more potential aircraft wingtip strikes based on the replacement counts in the index count array, wherein the digital aircraft structure comprises a plurality of protective envelopes around the aircraft. generating a digital base map of at least a portion of an aerodrome that includes one or more specific wingtip strike threats, the digital base map represented by a plurality of aerodrome cells; generating a digital aircraft structure representative of an aircraft, the digital aircraft structure represented by a plurality of aircraft cells; characterised by: assigning a numeric value to each of the aerodrome cells, the numeric value assigned to each aerodrome cell representative of the specific wingtip strike threat, associated with that aerodrome cell; generating an index count array, the index count array having a separate entry for each numeric value; determining whether a portion of the aerodrome cells are or would be replaced with the plurality of aircraft cells; counting each numeric value of the aerodrome cells that are or would be replaced to determine a replacement count associated therewith; entering the replacement count associated with each numeric value into the separate entry in the index count array for that numeric value; detecting one or more potential aircraft wingtip strikes based on the replacement counts in the index count array, wherein the digital aircraft structure comprises a plurality of protective envelopes around the aircraft. assigning a numeric value to each of the aerodrome cells, the numeric value assigned to each aerodrome cell representative of the specific wingtip strike threat, associated with that aerodrome cell; generating an index count array, the index count array having a separate entry for each numeric value; determining whether a portion of the aerodrome cells are or would be replaced with the plurality of aircraft cells; counting each numeric value of the aerodrome cells that are or would be replaced to determine a replacement count associated therewith; entering the replacement count associated with each numeric value into the separate entry in the index count array for that numeric value; detecting one or more potential aircraft wingtip strikes based on the replacement counts in the index count array, wherein the digital aircraft structure comprises a plurality of protective envelopes around the aircraft.