Questions about UXO Land extension forward modelling custom munition

MatissBrants

Hello!

I was editing the "UxaForwardModelTable.xml" file to add new munitions for forward modelling as per UXO Land extension documentation, but noticed that some lines of the code are not doing anything. It seems that the only parameter controlling the magnetic signature is the <Magsize> tag. I added two test munitions: 1) one with the size of 3x3x3 meters (Length x Width x Tickness), 2) and another one of 1x1x1 millimeter size, for extreme comparison. The Magsize for both of these was set to 0.5. The forward modelling creates identical magnetic signatures for both munitions.

So I have two questions:

1. The documentation explains that "For the magnetic response, the mag Size parameter is a scaled magnetic moment.". Is there some more documentation that explains this and how it is implemented in the code in more detail?
2. How can I make elongated munition, i.e., like a metal pipe, since the <length> tag doesn't control anything? It obviously would create a different mag signature than a round munition.

Thank you in advance!

Here is the code I used.

<?xml version="1.0" encoding="utf-8"?>
<Munitions>
  ...
  <Munition>
    <Type>Sphere</Type>
    <Description>Sphere 3 m</Description>
    <Length unit="mm">3000</Length>
    <Width unit="mm">3000</Width>
    <Thickness unit="mm">3000</Thickness>
    <Gates>
      <Gate name="Gate 1" gatetime="0.216" unit="ms">
        <Betas>
          <Beta index="1">61.279</Beta>
          <Beta index="2">48.67</Beta>
          <Beta index="3">25.267</Beta>
        </Betas>
      </Gate>
      <Gate name="Gate 2" gatetime="0.366" unit="ms">
        <Betas>
          <Beta index="1">51.967</Beta>
          <Beta index="2">41.141</Beta>
          <Beta index="3">18.604</Beta>
        </Betas>
      </Gate>
      <Gate name="Gate 3" gatetime="0.660" unit="ms">
        <Betas>
          <Beta index="1">40.361</Beta>
          <Beta index="2">31.753</Beta>
          <Beta index="3">12.244</Beta>
        </Betas>
      </Gate>
    </Gates>
    <MagSize>0.5</MagSize>
  </Munition>
  <Munition>
    <Type>Sphere</Type>
    <Description>Sphere 1 mm</Description>
    <Length unit="mm">1</Length>
    <Width unit="mm">1</Width>
    <Thickness unit="mm">1</Thickness>
    <Gates>
      <Gate name="Gate 1" gatetime="0.216" unit="ms">
        <Betas>
          <Beta index="1">61.279</Beta>
          <Beta index="2">48.67</Beta>
          <Beta index="3">25.267</Beta>
        </Betas>
      </Gate>
      <Gate name="Gate 2" gatetime="0.366" unit="ms">
        <Betas>
          <Beta index="1">51.967</Beta>
          <Beta index="2">41.141</Beta>
          <Beta index="3">18.604</Beta>
        </Betas>
      </Gate>
      <Gate name="Gate 3" gatetime="0.660" unit="ms">
        <Betas>
          <Beta index="1">40.361</Beta>
          <Beta index="2">31.753</Beta>
          <Beta index="3">12.244</Beta>
        </Betas>
      </Gate>
    </Gates>
    <MagSize>0.5</MagSize>
  </Munition>
</Munitions>

LauraQuigley

Hi there - thanks for asking this question. I have been looking into this, and believe that we are using the magnetic moment as the only value needed to model the magnetic response of an object. This can be thought of as small magnetic objects (dipole sources) have a relatively small magnetic moment, while larger magnetic objects have larger magnetic moments (larger dipole), in the presence of an external field. Therefore, whatever you enter as the magnetic size, will be the only way to describe the source you are trying to model. In this sense, you can not model different shapes, just different strength dipole sources. I will continue to look for documentation on this and post it when found. This also appears true for EM modelling, which essentially is using just the values of the polarizabilities. The length, width and thickness are just descriptors.