I don't like them either, but why are they invasive?
- They actively image your naked body. Metal detectors do not.
- They record said image of our naked body for an indefinite amount of time. Metal detectors do not.
- A human views the image of your naked body, and makes a subjective assessment of whether or not something suspicious has been detected, based on a wide range of parameters. A metal detector is a simple on/off detection based on an extremely narrow range of parameters.
In short, they are invasive because a human is involved. Let's not forget the cases (now rarer) of TSA agents guffawing at each others' penis sizes, or deliberately checking out women in the scanner, etc. My objections against the scanners would be greatly nullified if:
- All decision making is made via computer. No human ever sees the image.
- All images are immediately discarded. No record of the scan exists except the result.
- The parameters of detection are open and transparent.
The invasiveness of the scan has less to do with the scan and more to do with the tremendous opportunity for abuse it represents - both at the low level (individual TSA agents) and high level (as a matter of policy).
I've been flying more in the past few months, and the TSA has always been courteous and professional in those instances.
I don't know if something changed or it's all luck of the draw, but things seem much better these days.
(More detailed write-up: https://news.ycombinator.com/item?id=6279027)
The TSA says that there is no human in the loop and that they are no longer storing images. I don't know how much trust and credibility they have left these days (esp. after claiming xray scanners were perfectly safe to use).
Imagine you wanted to fight a decision later in court ... assuming that's possible ...
By contrast, the full-body scanners bombard you with very mild radiation and capture results, giving the operator a view of your body and whatever you have on your person.
It's a good deal more invasive.
And the current scanners don't give an image, just a "OK" or an outline with a location to check.
As for the rest, well, just because the operator doesn't see it doesn't mean the image isn't still being taken/saved/consumed down the road.