A USGS Marine and Coastal Studies Skill Training Module

1C. Positioning the boat

The diagram on the right shows key points in positioning the boat to core and assessing the site for anchoring. Details are discussed in the videos and outlined below.

Positioning Diagram:

Bow
Anchor

0

30

1C1. Locating - Video 1C1.

* Coring sites will have been predetermined by using seismic cross sections.

* The location of a coring site can be readily located using a global positioning system (GPS) chart.

* When the site is reached, a marker buoy is thrown over the side which is usually accurate to within 6 feet.

* After the buoy is thrown the boat is backed down to avoid running over the buoy. When the boat is at a dead stop in the water the captain will assess the wind and current to determine how to deploy the bow and stern anchors.

1C2. Assessment - Video 1C2.

* Set the anchors upwind and into the current so that the boat can be drifted down to the marker buoy.

* The bow anchor must be set to form a 30 degree angle into the wind in order for the boat to remain stable.

* If an anchor breaks free during a coring operation it will usually break the core and damage the equipment.

Stern
Anchor

Boat

Core Site

Lubber Line

1. Locating the position

Two point (bow+stern) anchoring scheme: