Ninety percent of excavation costs on most Unexploded Ordnance (UXO)/ Munitions and Explosives of Concern (MEC) projects are related to removing scrap metal that does not represent an explosive hazard. Advanced time-domain electromagnetic induction (TEM) systems and response modeling software – both developed under Strategic Environmental Research and Development Program (SERDP) and Environmental Security Technology Certification Program (ESCTP) research efforts – offer to significantly reduce the quantity of scrap metal that needs to be removed during a MEC cleanup project. This generally comes about by using the system response model to extract parameters characteristic of the metal item being measured by the sensor and comparing these to a library of munitions parameters. If a good match ensues, the item is classified as munitions and flagged for excavation. Otherwise, the item is either classified as clutter and deemed safe to leave in the ground or flagged for further scrutinization. The objectives of the data collection for the MR-201424 project were to:

  1. Produce three classification libraries of polarizability curves for common munitions, each with a different decay length – i.e. 3, 8 and 25 ms – corresponding to the standard dynamic and static mode settings proposed by Geometrics for their advanced TEM systems. The libraries will then be applicable to all advanced TEM sensors – past and future – with the particular library being used depending on the acquisition parameters chosen during data collection.
  2. Include a standardized complete set of metadata for all munitions item entries.
  3. Acquire data over less common munitions to expand the existing libraries’ munitions inventory.
  4. Develop a standard operating procedure (SOP) that will allow members of the community to make their own additions to any, or all, of the classification libraries.

The performance objectives for the data collection were established and validated during the first phase and reported on in a technical report. These provided the basis for evaluating whether or not the data collected were successful in meeting the project objectives and has been incorporated into the SOP (Standard Operating Procedure).

The first three performance objectives ensure that the requisite amount of data was collected for each munitions item on the library inventory list. The fourth applied to all data sets collected specifically for the purpose of extracting polarizability curves to add to the libraries and ensured that these estimated curves were sufficiently accurate. The fifth and sixth performance objectives apply to ensuring that the system responds to a standard object as expected (i.e. calibration) and that it remains stable throughout the collection period (i.e. repeatability).

Technology Description

Three different sensor systems were used during the initial phase of the data collection: a modified PortablE Decoupled ElectroMagnetic Induction Sensor (PEDEMIS); a Time-domain ElectroMagnetic mTADS (TEMTADS) 2x2; and a MetalMapper (MM). All systems are based on hardware technologies developed by G&G Sciences over the years through Naval Sea Systems Command (NAVSEA), SERDP and ESTCP funding. The PortablE Decoupled ElectroMagnetic Induction Sensor (PEDEMIS) was modified specifically for this project so that it effectively acted as a TEMTADS 3x3. The added spatial coverage that the 3x3 offered over the 2x2 (i.e. by the extra five transmitter/receiver sensor combinations) provided additional "look angles" to the target and helped in the determination that the estimated polarizability curves were indeed intrinsic to the munitions tem. In this way, use of only the MM was justified for the second phase of the data collection.

Demonstration Results

The calibration and repeatability measurements for all the advanced TEM sensors used during Phase 1 and 2 of the data collection followed the SOP developed during the project and used a medium schedule 80 ISO (ISO80) as the standard object of choice.  Based on Phase 1 results, it was determined that the different advanced TEM sensors respond to an object in the same way, thus justifying using only the MM for the Phase 2 data collection

As far as measurements made on each item, although every effort was made to follow the SOP by acquiring the requisite six orientation/range scenarios, there were instances where this was not always possible nor practical. In these few cases, only the most efficient set of measurements scenarios were conducted with safety being the main concern.

Implementation Issues

The four objectives of the data collection have been achieved:

  1. Three classification libraries of polarizability curves at 3, 8 and 25 ms decay lengths have been created for common munitions;
  2. Each munitions item entry to the libraries is accompanied by a standardized complete set of metadata;
  3. A number of less common munitions have been added based on requests made from the larger MR community; and
  4. An SOP (Appendix C) has been developed that will serve as a guideline for others wishing to collect high quality data in order to add more items to the libraries.

The final library product has been packaged in two different HDF5 formats: a library munitions item HDF5 file and a library self-contained raw data HDF5 file. The former format contains the munitions item metadata along with the inversion results for all the data collected over the particular munitions item, with a different HDF5 file created for each of the three libraries/decay lengths. The self-contained format is essentially the raw data file (i.e. the HDF5 data file that next generation Geometrics sensors are planning to dump) with the item meta data and inversion results – including the background data and a data mask that were both used with the raw data to give the inversion results – all embedded within the original file.

UX-Analyze is expected to import library self-contained format HDF5 files and use the raw data and background to generate both single- and multi-solver entries. Depending on the data being imported, the entries will be for a particular munitions item for one of the three libraries/decay lengths.