tattoos of offenders have been captured at time of booking for many decades now. These are typically referenced by a text description, so entering the word “scorpion” will fi lter out just those images that include scorpions. While this can be useful, it’s far from foolproof—different of-
L
fi cers can call the same content by different names; it may not be obvious what’s actually in a complex tattoo so certain shapes can be easily missed, etc.
appear as a different shape when viewed from different angles. In many instances, the tattoo will be partially hidden, which means that the full range of differentiating characteristics may well not be visible. So a tattoo can be of anything, be anywhere on the body, be of
ike mugshots, images of scars, marks, and
any size, and may only be partially visible. This is the challenge, and it’s only now being satisfactorily met. Because of the complex- ity, tattoo enrollment times are longer than those for face or fi nger- print enrollment. The enrollment process involves analyzing the image to fi nd
small areas that have suffi cient content, such as lines crossing at certain angles, that are distinctive. The system attempts to fi nd a number of these areas, after which their characteristics are trans- formed mathematically into a digital string. This string then be- comes the unique digital signature of the tattoo. Once enrolled, database search speeds can be extremely fast.
This is because, as with fi ngerprint or face recognition, the match- ing process doesn’t involve matching images, but rather compares the digital strings of an unidentifi ed tattoo against the strings of all the tattoos in the database, sorting the results into order of match percentage, and then displaying the images for an offi cer to visu- ally confi rm the correct match. It should be emphasized that tattoo recognition, like face recogni-
tion, doesn’t display the ‘positive match’ message so loved by Hol- lywood. It’s more like a Google text search, where the top matches are displayed for the user to make the fi nal call. The actual match may not be number one on the list, but should be near the top. Because during the booking process a description of an SMT
Full Scorpion Match
is typically included, a text fi lter on this fi eld can further narrow down the search, so that even with a partial shot of a tattoo and a very large database, the matching tattoo can be found. Each poten- tial match that’s displayed will include the name associated with it, and this links directly back to the offender’s full record. When the text fi lter “scorpion” is applied, non-scorpions are excluded, as shown here: Since the software sees a collection of distinguishing features
While face recognition as a software application is now fairly commonplace as a means of identifying an unnamed face, tattoo recognition is much more complex. This is because a mugshot has predictable characteristics, so the software knows what to look for. However, with scars, marks, and particularly tattoos nothing
is predictable. The tattoo can be of anything, from a simple small circle to a highly complex full-body work of art, and can be vir- tually anywhere on the body. This unpredictability has severely inhibited the development of effective tattoo recognition technol- ogy until now. In addition, different tattoo artists may draw the same object
very differently, so when trying to match, for example, a common gang marking, one artist’s view can be suffi ciently different from another’s that any two images may well not match. As computers continue to have ever-increasing power, they’ve reached a level where modern systems now have the number- crunching capability to process the myriad of analyses and calcu- lations necessary to fi nd suffi cient unique characteristics to enable one tattoo to be differentiated from another. An example of how well this can now work is shown above. In the real world, additional issues have to be taken into account. Tattoos, being drawn on fl esh, are subject to being distorted, and
rather than an image of a scorpion, it may return images that have similar features but are not of scorpions. A cause of this with tat- toos is that an artist may use the same style across a range of dif-
Scorpions with Filter
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