A look at alternatives to full body scanners

The use of full body scanners has recently sparked a lot of controversy in the US. I already reported on my own experience being scanned by such a scanner (see here). I will now put my scientific lab-coat on and discuss some possible alternatives. Let me be clear: I don’t know for sure how efficient these could be and how they could be implemented at the airport security check points, but I try to give some elements of comparison.

  • Weighting: At the security check, with shoes and jacket off and empty pockets, your weight is roughly proportional to your body volume. A simple camera system can make an estimate of your body weight and compare it to the real value using a simple scale on which you step; if the measured value is too far away from the estimate maybe there something you left in your pocket. The big limitation of such a system is the uncertainty on your actual body weight that can trigger a lot of false-positive or on the opposite miss a lot of mismatch.
  • Infra-red camera: Our body produce a visible image in the infra-red spectrum, any object one carries in its pockets might change the heat signature and be visible on an infra-red image.
  • Ultrasound: There’s no question to give you a sonogram yet ; but a somehow similar system might be able to measure the density of what is under your clothes ; concealed objects could be detected that way.
  • Sniffer: If a terrorist moves around with a bomb around its waist, there a chance that the explosive releases small amount of molecules in the air around. These molecules might not be detectable by a human nose, but a chemical spectrometer might be able to detect unusual molecules around a person.

My opinion, regarding those options is that X-rays and millimetric waves scanner as currently used in the airport combines all the advantages of the probes above.

However efficient any detection technics could be the burden of keep flights safe should not be on the airport check point; it is just a last line of defense, but if a terrorist gets to the airport with a plane tickets, some people in the intelligence and counter-terrorism offices did not do their job well enough.


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