This week I took a short trip to Denver for some specialized software training. The training was sponsored by the Department of Defense (DOD) to encourage contractors involved in munition remediation to learn and use newly available advanced electromagnetic (EM) sensors and their associated software modules. I mentioned in a previous blog post that in the field of munition remediation, the Holy Grail is to not only detect munitions in the ground but also to discriminate them from non-hazardous scrap metal. By doing so the government could save hundreds of millions of dollars by not digging up inert scraps of metal.
It is now possible to discriminate between the two by using advanced electromagnetic sensors with an array of multi-axial transmit and receive coils. With this technology, it is possible to measure the decay curves of the electromagnetic fields induced in an object. We can then used specialized software to analyze the data and perform a complicated inversion problem to determine the polarizability or Beta values of the target. The Beta values of an object are determined by its shape, material type, and mass. There are three Beta values for every object (we live in a 3D world). This is where it starts to become a little easier to understand. A cylinder will have one value larger than two other equal Beta values. On the other hand, a disk-shaped object will have one Beta value that is lower than the two other larger and equal Beta values. These Beta values can then be referenced against a library of know objects to statistically categorize the unknown target.
Ok, so that paragraph is the short version of years of both hardware and software development. This has been a collaborative effort of the government, private sector and universities. Just a few years ago this technology did not exist. And while I may not have a chance to use the advance EM sensors any time soon, it was a great opportunity to learn more about the process and get hands on experience processing data.
In the underwater world of munition surveying we are at least a decade behind terrestrial technology in our ability to remediate munitions. But by staying current with the terrestrial technology we will be better positioned to implement the best techniques as they become feasible.
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| An advanced electromagnetic sensor called the metal mapper (www.geometrics.com) |
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