data analysis – Page 3 – NOAA Teacher at Sea Blog

May 30, 2006March 18, 2021

Jeff Lawrence, May 30, 2006

NOAA Teacher at Sea
Jeff Lawrence
Onboard NOAA Ship Rainier
May 22 – June 2, 2006

Mission: Hydrography survey
Geographical area of cruise: Alaska
Date: May 30, 2006

AB Leslie Abramson & Chief Steve Foye piloting the ship

Weather Data from Bridge as of 0730 Hours:
Visibility: 10.0m miles
Wind direction: 350 deg. (N)
Wind Speed: 2 knots
Sea level pressure: 1018
Present weather: Scattered cirrocumulus clouds, sun shining brilliantly – It’s a beautiful morning in SE Alaska.
Temperature: 49 deg. wet/dry 50 deg.

Science and Technology Log

Earlier this week I went out on launch RA 6 to run some lines off Biorka Island. The weather was a little dreary and cold but made much warmer by the crew, which consisted of Chief Boatswain Steve Foye, AB (Able Body Seaman) Leslie Abramson, and LTJG (Lieutenant Junior Grade) Nicola Samuelson.

LTJG Nicola Samuelson collecting sonar data aboard RA 6

Seas were a little rough running between 4 and 6-foot swells, but the crew did an excellent job staying on their lines and completing the task assigned. Conditions are not always ideal, yet the job must still be done. If seas are too rough the crew will head to a bay or protected area that still needs to be worked. Steering a boat in rough sea conditions isn’t easy. Chief Foye was on board to assist AB Abramson if needed. Leslie did an excellent job controlling the boat while down below LTJG Samuelson was collecting the data from the sonar. LTJG Samuelson has finished her 2-year assignment with the RAINIER and will be heading to Rhode Island for her next duty station when we reach our next port stop of Juneau.

Personal Log

This day was an interesting one. I learned when you feel nausea or seasickness it is better to eat something even though you don’t fell like doing so at the time. I really enjoyed learning so much about the day-to-day data collection techniques used by the crew of the RAINIER. The equipment is quite sophisticated and the people using it are very well trained. LTJG Samuelson was very helpful in explaining how the data is collected, stored, retrieved, and used to make the nautical navigation charts that NOAA publishes. The boatswain crews are well trained and do a good job piloting the launch boats through strong tide currents, rocky coastlines, and even rough seas.

Questions of the Day

How deep is a fathom?

When a ship anchors there are red, white, and blue chain links to show how deep the anchor is. What is the length between these colors called?

How long is this length of chain?

How much does one anchor on the RAINIER weigh?

How much does one marked length of chain weigh on the RAINIER?

What is the keel of a ship?

What is meant when people are talking about a ship or boats draft?

What does it mean when a ships bell rings continuously for 5-6 seconds every minute when it is anchored in open water?

Thanks to Ordinary Seaman Megan Guberski for helping me to pose and answer some of these questions.

May 29, 2006March 18, 2021

Jeff Lawrence, May 29, 2006

NOAA Teacher at Sea
Jeff Lawrence
Onboard NOAA Ship Rainier
May 22 – June 2, 2006

Mission: Hydrography survey
Geographical area of cruise: Alaska
Date: May 29, 2006

Laurel Jennings & Tonya Watson Nick Gianoutsos — Laurel Jennings & Tonya Watson

Weather Data from Bridge
Visibility: 10.0 miles
Wind direction: 290 deg. (WNW)
Wind Speed: calm
Sea level pressure: 1016
Present weather: scattered to mostly cloudy skies, calm winds
Temperature: 48 de. wet/dry 50 deg.

Science and Technology Log

Today I visited the plot room. It is always a busy place. After the data has come in from the launch boats which have run the lines they were assigned for that day, the data is then downloaded to computers for processing so that accurate navigation charts can be made. Nick Gianoutsos and Shawn Gonzales both showed me how they clean up the data so it can be processed to make charts of the bottom of the channels, narrows, and waterways used by navigators throughout Alaska. The final product must both be accurate and reliable so that ships can trust the charts they are reading and using to plot navigation points and travel safely through hazardous coastal areas.

Wrangell Narrows is where the data has been being collected from for the past couple of weeks. Wrangell Narrows extends almost 21 miles from the Sumner Strait to the south up to Frederick Sound to the north, near Petersburg, Alaska. The channel is very narrow in places, with dangerous ledges and strong tidal currents, and can be a treacherous waterway for larger boats if not marked and navigated properly. Cruise ships, Alaska State Ferries, tugs and barges, freight boats, pleasure boats, and commercial fishing boats navigate the channel. Some of the cargo that travels through the Narrows includes: lumber products, fish products, petroleum products, provisions, and general cargo. There are no roads to Petersburg, so everything has to come by boat or plane. The narrows can be a busy place for traffic in this area of Alaska. All known dangers in the Narrows are charted and most are marked. The mean range of the tide is 13.4 feet and diurnal range is 15.7 feet at Petersburg.

Members of the crew aboard the NOAA ship RAINIER are entering and analyzing data from the survey lines run from the launch boats during the day. This data will give an accurate indication of what lies below the water and also what lies above it. The crew aboard RAINIER keeps working, long after regular work hours are over. Crunching the numbers from a launch into useable data for charts for navigation.

Personal Log

Today I was privileged to see a part of Alaska, Biorka Island, which is northwest of where we were near Petersburg in the Wrangell Narrows. The change of scenery was exciting and nearby are hot springs which are very warm and relaxing according to some of the crew who spent time there after hours.

Question of the Day

Using the information from log #4, which was Thursday’s log, how long will it take a ship that travels at 15 knots per hour to transit 231 miles?

July 8, 2004March 18, 2021

Sena Norton, July 8, 2004

NOAA Teacher at Sea
Sena Norton
Onboard NOAA Ship Rainier
July 6 – 15, 2004

Mission: Hydrographic Survey
Geographical Area: Eastern Aleutian Islands, Alaska
Date: July 8, 2004

Location: Sonar Patch cruise, SE of Devils Bay on AK peninsula
Latitude: 55 46.163 N
Longitude: 158 03.557 W
Visibility: < 1 nm
Direction: 229 degrees
Wind Speed: 16 kt
Sea wave height: 1-2 ft
Swell wave height: 1.2 ft
Seawater temperature: 8.9 deg C
Sea level pressure: 1021.1 mb
Cloud Cover: n/a fog
Weather: Fair and foggy, 8.9 deg C dry / 9.4 deg C wet

Plan of Day: 1.5 days of sonar readings in patch with lines of 2.5 hours each. Launch #5 boat for survey north of ship around a possible rock pinnacle.

Science and Technology Log

Sonar Systems on board RAINIER: How they work.

What is Sonar?

In its most basic sonar are sound waves that are produced and then bounced back off of an object and recorded. Since the speed of sound is a known figure, the amount of time it takes for the sound wave to return to the transmitter/receiver gives a collectable image of that object. The deeper objects are the longer the sound wave takes to bounce back. Two types of sonar are single beam and multi-beam. Single beam is able to give high detail to an object but only shows a narrow swath, while multi-beam has a large footprint and can show a larger over all area. There are limits to the depth sonar can go because of the density of the water column. If the water is very dense the sound waves are slowed down and do not transmit the correct timing, therefore the image will be distorted. All images created must be analyzed after the density, temperature and salinity of the water column is taken into consideration.

Sonar is a very powerful sound wave and it can be dangerous, although it is at a frequency that humans or marine mammals cannot hear. If a diver were scanned they would be susceptible to a high-level concussive power. The emitter itself requires a large volume of power and if a human were to be near it during an emission it would do a great deal of damage. Think of the concussion from a bomb or firework, sonar is many, many more times as powerful.

RAINIER’s Sonar:

The ship is equipped with a deep sonar transmitter; it is attached to the hull and is used for scanning deep water where resolution is not a large issue. The boat “mows the lawn” in a patch of ocean. Each pass is numbered and the data collected. The lines are about 2 hours at 7-8 knots long. For more detailed work or a smaller area the ship will use one of its 6 launches that are also equipped with various sonar transmitters. These small boats will conduct and similar pattern of lines and collect the data right on board. The data is then transferred to the computers on board to go through technician cleaning and final analysis.

Sonar Types:
Single-beam – one beam sent and received.

Multi-beam – up to 240 beams per 180 degrees sent and received. As depth increases the foot print widens.

Analysis of data:

When the soundings are collected they are run through a Carris computer program where the technicians can manually scan each line. There are techs assigned to each “sheet” or area. Each line is cleaned, meaning outliers are removed or other “noise” is deleted. Once the data is clean a complete 3-D image of the patch can be looked at with all the data points represented. Once an entire area has been scanned objects become very clear, as if you were looking at them. From outlines of sunken ships from the side to large monolithic rocks protruding from the ocean floor, the detail and accuracy of the image is amazing. Once there is enough data the sounds can be turned into color-coded overlays that fit right on top of the fathom charts, so as to give a 3-D view of what those fathom readings represent. Red and orange or shallow and the colors move through yellow, green and finally blues, which are the deepest readings. Mountain ridges, lava floes, old wrecks, valleys and monoliths all come to life on the chart.

Personal Log

Steve Foye gave me a quick training with another new member of the crew on the job of Lookout on the flying bridge last night. He reviewed the 32-point compass and the difference between saying North relative to the ship verses trying to figure out the “real” compass coordinate. He explained you could use directions (NW or SE) or give the coordinates (90 or 270). Dead ahead would be 000, north relative to the ship or 360, all are correct for locating something directly off the bow of the ship.

Question of the Day:

When is the ship required to sound foghorn and place lookouts on the Bow/Flying Bridge?

When the visibility gets below 1 nm the ship is required to blow the foghorn or ring a bell every 2 minutes. A lookout is placed on the flying bridge during hours of darkness or low visibility. They move to the bow when the foghorn is turned on so they do not damage their ears.