Grad student Courtney was asked by Chief Scientist Nicholson and also Kennett and her sedimentologist advisor Rick Behl (Cal State Long Beach) to position a core so that it cored the interval above what was cored by us in 2005. They asked that the new core penetrate 1 m of the top of the rock cored in 2005. We positioned the core 75 m to the east of the older core. We assumed that the new core would be 3 meters-long. Preliminary analysis suggests that the overlap is 60 cm, which is a better result than a 1 m overlap.

This precision would not be possible without things like GPS. The captain can position the corer within maybe 2 or 4 meters horizontally. They have to correct the position of the corer for the position of the GPS antenna. We (Warren and I) have to correct the position of the source of the very high resolution chirp seismic for the distance to the GPS antenna. We site the cores using the chirp seismic, using the software "The Kingdom Suite" which is donated to us and other academic institutions by Seismic Micro Technology.

In my household, HW wins the prize for precision. She was Chief scientist with Bill Ryan on the first cruise to use an Autonomous Underwater Vehicle (AUV) for research. The AUV was doing bathymetric surveying in 2 or 3 km water depth on the East Pacific Rise. HW had to correct the 40 cm distance between source and receiver on the AUV. For a project to map the bottom of the Hudson River, she had to correct for tides.

We will see the vertical affect of tides here, because there had been almost a 3 meters tide range the last couple of days. In two-way travel time for sound in water, this would be about 4 or 5 millseconds. We can see this by comparing our chirp seismic to the existing multibeam bathymetry. Or, at least we could see it if we had the time to figure it out.

Smoky day over the Channel.
Chris.