NOAA Teacher at Sea
Victoria Cavanaugh
Aboard NOAA Ship Fairweather
April 16-27, 2018
Mission: Southeast Alaska Hydrographic Survey
Geographic Area of Cruise: Southeast Alaska
Date: April 24, 2018
Weather Data from the Bridge
Latitude: 50° 10.002′ N
Longitude: 125° 21.685′ W
Sea Wave Height: 7 feet
Wind Speed: 5 knots or less
Wind Direction: Variable
Visibility: 14 km
Air Temperature: 9oC
Sky: Mostly Sunny
Science and Technology Log
NOAA Ship Fairweather has begun its transit to Alaska for the heart of the field season which means transiting the famous Inside Passage, a roughly two day voyage through a stretch of nearly a thousand islands between Washington State and Alaska. The more protected waterways of the Inside Passage provided a smooth, calm ride. I took advantage of the transit to spend more time on Fairweather‘s bridge in order to learn a bit about navigation.
One thing that quickly became clear on the bridge of Fairweather is that for many navigational tasks, the crew has at least three ways of being able to obtain needed information. For example, navigational charts (maps) show two compasses: magnetic and true north. The inner circle represents the magnetic compass, which in reality points 17 degrees right of true North and is dependent upon the pull of the Earth’s magnetic core. Because the magnetic compass can be offset by the pull of the ship’s magnetic fields (the ship is made of steel, after all), Fairweather’s compass is actually readjusted each year. During our Inside Passage transit, a specialist came aboard near Lopez Island to reset the ship’s magnetic compass.
The ship’s magnetic compass is located on the flying deck, just above the bridge. So, to be able to read the compass from the bridge, the crew looks through a series of mirrors above the helm. Notice that next to the mirrors, is a digital display that reads “78.” This is an electrical reading from the gyrocompass. The gyrocompass reflects “true North” also referred to as geographical North.
When at sea, a crew member on the bridge takes “fixes” every fifteen minutes, both day and night. To take a fix, the crew member uses an auxiliary compass and chooses three landmarks on shore as points. The crew member then lines up the viewfinder and records the degree of the line formed between the ship and the given point.
Next, the crew member plots the three points on the chart using triangles (similar to giant protractors). The point where the three lines intersect is the ship’s current location. Though technically, the crew could just plot two points ashore and look for where the lines intersect, but as a way of triple checking, the crew chooses three points. Then, if a line doesn’t intersect as expected, the crew member can either retake the fix or rely on the other two points for accuracy.
In addition to using the two aforementioned compasses to determine the ship’s location, the open seas often mean majestic night skies. Some of the crew members told me they also look to the stars and find the Big Dipper and North Star. A central theme on the bridge is being prepared: if both compasses malfunction, the crew can still safely guide Fairweather along its course.
In addition to being able to take fixes and locate constellations in the night sky, modern day technology can make the crew’s job a bit easier. The ship’s latitude and longitude is continually displayed by an electronic monitor above the helm via GPS (Global Positioning System). Below, the ship’s Electronic Navigation System (ENS) essentially acts as Google Maps for the sea. Additionally, the ENS provides a wealth of data, tracking the ship’s speed, wind, and other contacts.
Next to the ENS on the bridge is the ship’s radar, which shows other vessels transiting the area. Similar to ENS, the radar system also provides information about the ship’s speed and location.
Wind matters in navigation. The force and direction of the wind can affect both currents and the ship’s route. Winds may push the ship off course which is why taking fixes and constantly monitoring the ship’s actual location is critical in maintaining a given route. The wind can be monitored by the weather vane on the bow, the electronic wind tracker above, or on the ENS below. Additionally, a crew member demonstrates a wheel, used for calculating and recalculating a ship’s course based on the wind’s influence.
On the bridge, multiple ways of being able to perform tasks is not limited to navigation alone. Communicating quickly on a ship is important in case of an emergency. Fairweather is equipped with various communication systems: a paging system, an internal telephone line, cell phones, satellite phones, etc.
Personal Log
Just before leaving Puget Sound, I had the chance to go kayaking for a few hours with two of the crew members. We had great luck; not only was the water placid, but harbor seals played for nearly an hour as we paddled around one of many coves. It was neat to see Fairweather from yet another perspective.
Did You Know?
The Inside Passage is a series of waterways and islands that stretches from Puget Sound, just north of Seattle, Washington on past Vancouver and British Columbia and up to the southeastern Alaskan panhandle. In British Columbia, the Inside Passage stretches over more than 25,000 miles of coast due to the thousand or so islands along the way. In Alaska, the Inside Passage comprises another 500 miles of coastline. Many vessels choose the Inside Passage as their preferred coast as it is much more protected than the open waters of the Pacific Ocean to the immediate west. Nonetheless, rapidly changing tidal lines, numerous narrow straits, and strong currents make navigating the Inside Passage a challenging feat. In addition to frequent transit by commercial vessels, tugboats, and barges, the Inside Passage is also increasingly popular among cruise ships and sailboats. On average it takes 48-60 hours to navigate.
Challenge Question #4: Devotion 7th Graders – NOAA and NASA collaborated to produce the National Weather Service Cloud Chart which features explanations of 27 unique cloud types. Clouds can tell sailors a great deal about weather. Can you identify the type of clouds in the ten above pictures of the Inside Passage? Then, record your observations of clouds for five days in Brookline. What do you notice about the relationship between the clouds you see and the weather outside? What do you think the clouds in the pictures above would tell sailors about the upcoming weather as they navigated the Inside Passage? Present your observations as journal entries or a log.
A Bonus Challenge. . .
Just outside the bridge on both the Fairweather‘s port and starboard sides are little boxes with two thermometers each. What is the difference between dry and wet temperatures? Why would sailors be interested in both measurements?
