A method of protecting against impact between a vehicle and a physical structure of a facility having an opening for the vehicle to pass through includes defining a monitored plane relative to an edge of the opening, the monitored plane defined by a plurality of baseline measurements, wherein each of the plurality of baseline measurements: 1) corresponds to a distance between a sensor spaced apart from the edge and one of a plurality of virtual ends of the monitored plane, and 2) is identified by an angle parameter. The method also includes obtaining a subsequent measurement; evaluating the subsequent measurement relative to a corresponding baseline measurement to determine if a criterion indicative of an intrusion of the monitored plane is satisfied; and activating an alarm when the criterion is satisfied.