Geophysics – Oval Barrow – September 2013

Today a team of AVAS members visited a site near Fordingbridge where a possible oval barrow has shown up as a crop mark, as shown below.

Oval barrow cropmark

Oval barrow cropmark

On another vertical aerial photo, we were able to roughly position a 20m square for survey with the geophysics equipment.  This is shown below, with the ditch shown as an arc across the grid square.:

Oval barrow 20m square

After some difficulty accessing the site, our arrival was greeted with a hefty rain shower.  After measuring in the grid square, we were able to get started with the survey.

Geophysics at possible oval barrow, near Fordingbridge

While taking readings, we remarked on a number of occasions how there seemed to be no pattern to the readings.  Mark appeared from a hedge to lend a hand part way through, and we managed to complete the readings by lunchtime.  While the data was downloading, we again discussed our concerns that the readings had seemed fairly random.  It was therefore with great surprise that the plots actually picked up the ditch seen in the crop mark, as shown below (click on the image to see it a full size).

Resistance survey possible oval barrow

The above plots show different visualisations of the readings in the square.  When comparing the plot to the crop mark (above), you need to rotate the plot square nearly 90 degrees anti-clockwise.  Coordinates (0,0) in the plot are positioned at the bottom corner of the red square on the crop mark, and the bottom of the plot runs along the right edge of the red square on the cropmark.  If you are now not more confused than ever, you can see that the curving feature in the plot corresponds almost exactly to the ditch shown in the cropmark.  Also of interest is the area of high readings to the bottom right of the plot, and the fact that the arc of low readings seems to widen as it turns near the bottom right of the plot.

While doing the survey, a couple of nice worked flints were found on the surface of the field.  One of these is shown below, and is approximately 43mm in length.

Flint found during geophysics

We now have less than three weeks before the field is drilled to survey more squares.  Thanks to everyone for giving up their time today.

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2 Responses to Geophysics – Oval Barrow – September 2013

  1. Pingback: Geophysics – Oval Barrow – Part 2 | The AVAS Blog

  2. Pingback: Geophysics – Oval Barrow – Part 3 | The AVAS Blog

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