Bill Lindquist: Setting Benchmarks, May 7, 2013

NOAA Teacher at Sea
Bill Lindquist
Aboard NOAA Ship Rainier
May 6-16, 2013

Mission: Hydrographic surveys between Ketchikan and Petersburg, Alaska
Date: May 7, 2013

Weather on Board
15 C
Wind at 7 knots
Clear skies

Science and Technology Log: Setting Benchmarks

To conduct accurate surveys of the ocean bottom, clear reference points must first be established. Today, I joined a shore team to permanently set official benchmarks into the rock. Yesterday a team located two existing benchmarks in Burroughs Bay, including one put in place in 1891. A hole had been chiseled into the rock followed by a circle around it and an “X” crossing through the hole from one side of the circle to the other. Above the letters B and M (benchmark) were carved in the rock. Weathering and plant growth provided a challenge. There is something intriguing in the transcendence of time, updating work that was performed over a century ago.

To establish a vertical standard, three new brass benchmarks were cemented into rock with the intention of lasting into the next century. All five benchmarks were precisely located to reference elevation to local tidal data acquired through an electronic tidal gauge installed to capture 30 days of high and low tide data. A diving team anchored one end of a line underwater well beyond the reach of low tide. The other end rose on land high enough to be protected from high tide. These tidal data will be referenced to a visual measurement taken every six minutes for three hours from a vertical staff we installed.

Tomorrow a team will install a horizontal control (horcon). A marker was affixed on an island that would collect location data from Global Positioning Satellites (GPS). GPS data is close, but lacks precision. The variance in GPS data will be referenced to the precise location of the horcon to establish an accurate and stable benchmark for all the survey data we will be making.

This preparation and collection of vertical and horizontal benchmarks all come together to provide referential data utilized in the precise creation of updated nautical charts.

Personal Log: Life at Sea (continued)

I had the good fortune to join the Rainier community on the first leg of the 2013 field season and experience early preparation drills and equipment training. En route from Ketchikan to Behm Canal, ship wide emergency drills were conducted to ensure everyone is fully prepared for a quick response to any situation that might arise. The fire drills I am familiar with is limited to getting all kids safely out of the school building, doing a head count to assure all are accounted for, waiting for the all clear, and bringing them back in. A call is made to the fire dept to respond if necessary.

At sea, the fire department is the community on board the ship. Should an emergency arise, lives depend on the preparedness of every individual on board. Our fire drill was an authentic drill. A fire alarm signaled the bridge there was a fire in the laundry room. The bridge quickly alerted all hands on deck. Everyone reported to pre-assigned stations, head counts were made and reported in. The fire response team got the necessary equipment out and evacuated the smoke (the smoke was real). There was no fire department to call. Our lives depended on our own actions.

Another alarm alerted everyone to a catastrophic problem necessitating a call to abandon ship. All hands quickly grabbed their emergency flotation suits readily available in their state rooms and reported to pre-assigned stations where a head count was made. These suits, specially designed to keep us afloat and dry, were quickly donned. This was one we never had to practice in school.

Potentially dangerous work in remote locations necessitates carefully scripted and practiced safety habits. Teams go out in small boats to conduct any necessary work on shore and survey areas too shallow for the ship. All these teams must remain in radio contact and make hourly reports to the ship’s bridge assuring all are individuals are safely accounted for. Should anything happen, there are Rainier crew members that have received specialized medical training preparing them to respond to medical issues occurring on board.

At sea, lives of all on board are in the hands and actions of all on board. Preparedness is key. I am thankful for that commitment.

Did you know?

The speed of the ship is not controlled by changing the speed of the engine. The ship’s engines are most efficient when they can maintain a steady speed (revolutions per minute). Instead, the ship’s speed is changed by altering the pitch of the screws (propellers). As the screw turns in the water a difference in pressure from the front to back is created. This pressure difference creates thrust. The more inclined the blades of the screw are, the faster the ship will travel. There are times during the survey when the ship must come to a full stop. Even then, the propeller shafts continue to spin but rotate in a flat plane resulting in no thrust.