Regarding security on the gropunds outside the Pentagon, boots on the ground are the ideal surveilance mechanism. A live guard walking a beat can hear things. An intruder would have to make very careful observations over an extended period of time to determine where a guard might be at any given time, and then has to hope that the most hide-bound fool who always makes the same circuit at the same time has just passed his point of entry when he intrudes.
Having worked secruity, both civilian and military, I would not, nor would most people I know, keep to a rigid schedule, other than to rendevous with another guard for a mandatory report. It pays to be unpredictable.
Mechanical devices are easier to defeat by simple mathematic applications.
Most important areas covered by cameras are parking lots and entrances. Some of those required visual identification of the individual entering.
There is no reason to expect better coverage of the grounds.
To address the positioning of the cable spools, hopefully for the last time, the photograph shows them stood on end. They are heavy and probably subject to being over turned only by massive forces. I should expect the turbulence beneath an aircraft to have scattered them more laterally. I think they were skimmed by the fuselage. This would, of course, put the aircraft well over the surface of the lawn as it came in for impact.