Kathy Virdin, July 24, 2004

NOAA Teacher at Sea
Kathy Virdin
Onboard NOAA Ship Rainier

July 20 – 28, 2004

Mission: Hydrographic Survey
Geographical Area:
Eastern Aleutian Islands, Alaska
July 24, 2004

Latitude: 55 degrees 17.194 N.
Longitude: 160 degrees 32.23 W.
Visibility: 3 nautical miles
Wind direction: 100 degrees
Wind speed: 10 kts.
Sea wave height: 1-2 ft.
Swell wave height: 2-3 ft.
Sea water temperature: 10 degrees C.
Sea level pressure: 1002.0
Cloud cover: Cloudy with rain

Science and Technology Log

Today we went out on a launch (my first in the Shumagin Islands). We traveled near the area of Simeon Bight to run lines to check depth measurement. An example of why this is so important is that in one of their launches, they found after an earthquake, a 30 meter drop-off near a fault line. This wasn’t on any charts because it had been caused by the earthquake itself. Before they begin the depth measurements, it’s vital that they take a cast with the salinity, pressure and temperature instrument. This information is then hooked directly into the computer to be calculated into the depth findings, so that the depth can be corrected by these factors. We ran cross lines (lines that cris-crossed each other) as a quality check to be sure that no area had been missed. The transducer (which sends out a multi-beam swath of sound) is lowered into the water by a mechanical arm. This is high-tech stuff! The computers are also recording the GPS (global position system) location of our boat at all times. When we learn the depths of the waters we pass over, we have to know exactly where we are in order to record this on nautical charts. Out of 24 satellites, we need at least 5-7 within range plotting our location to ensure accuracy. The computers divide the screen into sections which show our depth reading, a picture of the ocean floor by sonar calculations and the range our instruments will accurately reflect. We have traveled a range of 88 meters in depth to 6.7 meters in depth. Interestingly, one possible technology that is being tested and may be the best method of the future is called Lidar, which means sonar transmitted from an airplane, which flies over coastal areas and can give a depth reading on land and in the ocean. The RAINIER is testing one area that has been measured by Lidar to compare our measurements with theirs to check their accuracy. This would be a safer method, since lowering the launch boats and retrieving them has a certain amount of risk.

We’ve just seen some lazy puffins that are swimming on top of the water, which makes them look like sitting ducks. As we return to the RAINIER in the late afternoon, we bring back a lot of data that the survey technicians will assess and correct to be submitted to the cartographers.

Personal Log

We had a rainy, foggy afternoon on the water while we were surveying, with clouds that hovered over the green, craggy cliffs. It makes a beautiful sight. We felt we got a lot accomplished and returned with some good data. In talking with various members of the crew, I’ve gotten some good ideas to use in my lesson plans as they help me think of ways to explain their operations that will simplify it, such as flashlights taped together to represent a multi-beam sonar swath. I’m going to catch up tonight on correspondence, and refine my lesson plan ideas tomorrow. I can’t wait to take all these ideas back to the classroom!

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