Tag: North Pacific

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Mike Laird, July 30, 2005

NOAA Teacher at Sea
Mike Laird
Onboard NOAA Ship Rainier
July 24 – August 13, 2005

Mission: Hydrographic Survey
Geographical Area: North Pacific
Date: July 30, 2005

Weather Data

Latitude: 55°37.1̍ N
Longitude: 156˚46.6 ̍ W
Visibility: 10 nautical miles (nm)
Wind Direction: 140˚
Wind Speed: 5 kts
Sea Wave Height: 0-1΄
Swell Wave Height: 2΄
Sea Water Temperature: 12.2˚ C
Sea Level Pressure: 1009.8 mb
Cloud Cover: Stratus

Science and Technology Log 

I would like to add some clarifying information to my log entry, Mike Laird, July 29, 2005.  In that entry, I discussed setting up two horizontal control-data collection stations, and in reading the entry, it appears that the purpose for both stations is to support the “fly-away” Differential Global Positioning System (DGPS).  This is not accurate.  Only the station we established on the point will be used to determine the exact location of the DGPS.

The purpose of the other station is to verify the accuracy of the existing benchmark at that site, so a tidal datum (“…a base elevation used as a reference from which to reckon heights or depths”) can be established for the tide station located there.  I mentioned in the previous log that the horizontal control team is responsible for establishing accurate latitude and longitude coordinates for each sounding taken by the RAINIER and the launches. In addition, the soundings are taken throughout the day at different stages of the tide, which means that water depth will vary.

It is the responsibility of the vertical control team to provide precise tide data for corrections that have to be applied to the soundings so that they meet NOAA’s Mean Lower Low Water (MLLW) guideline (ensures minimum water depth is charted).  Mean Lower Low Water means that an average is taken of the tide level at the lower of the two ebb periods in a semi-diurnal (two flood periods and two ebb periods every day) tidal day. The National Water Level Observation maintains primary control stations in many locations around the United States. These stations determine a tidal datum based on the average of observations over a nineteen-year period.

In many survey areas, the tidal datum received from a primary control station can be used to make the necessary corrections to the soundings.  However, the nearest station to the RAINIER’s current work area is located in Sand Point – a significant distance away.  Therefore, the vertical control team established the tertiary tidal station (one in operation for at least thirty consecutive days but less than a year) here in Cushing Bay, so that data more indicative of the local conditions can be collected and compared to the primary datum.  During this analysis, a decision will be made about any adjustments that need to be made to the primary datum before it is used to make corrections to the survey soundings.

Personal Log 

Our good fortune continues to hold – the weather is incredible.  Sun is shining brightly, temperature in the low 70’s.  We had been hearing whispers since lunch of a beach party tonight. The rumors were confirmed by an announcement following dinner that a skiff would be ferrying people to the shore and back from 18:30 until 23:30.  It was a time for the crew and guests to relax and hang out, enjoy a big driftwood bonfire, do a little beachcombing (the captain found a large whalebone – rib maybe), have some sodas and listen to a little music.  A lot of fun!

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Mike Laird, July 29, 2005

NOAA Teacher at Sea
Mike Laird
Onboard NOAA Ship Rainier
July 24 – August 13, 2005

Mission: Hydrographic Survey
Geographical Area: North Pacific
Date: July 29, 2005

Weather Data

Latitude: 55° 53.36 ̍ N
Longitude: 158˚ 58.4 ̍ W
Visibility: 10 nautical miles (nm)
Wind Direction: Light Airs
Wind Speed: Light Airs
Sea Wave Height: 0΄
Swell Wave Height: 0΄
Sea Water Temperature: 12.2˚ C
Sea Level Pressure: 1013.5 mb
Cloud Cover: Sky 8/8 covered;
Lower-level: cumulus, stratocumulus
Mid-level: altostratus

Science and Technology Log 

Today I am on a team that is going ashore to set up two horizontal control-data collection stations. The horizontal control team is responsible for establishing accurate latitude and longitude coordinates for the location of the survey soundings. The RAINIER uses a Differential Global Positioning System (DGPS) to acquire precise readings for every collected depth sounding. The remote location of the Mitrofania Island work area has introduced an infrequently encountered challenge for the horizontal control team.  The two Coast Guard operated DGPS Beacon Stations that are closest to the work area (one on Kodiak Island and one in Cold Bay) are too far away (we are on the outer fringe of their transmitting capability) for the signal to reach the launches in some of the more isolated, shielded areas. As a result, we are out setting up the horizontal control data collection stations.

The first station is set up over an existing benchmark and will record data transmitted directly from a GPS satellite.  The receiver will record readings for six hours, shut down for twenty-four hours, and resume recording for a final six-hour time period. Finished with the first station, we travel across the bay to a point that extends out into the ocean. We will set up the second horizontal control data collection station at this location. However, there is not an existing benchmark, so we must establish one.  First, we drive three-foot sections of metal rod into the ground (normally benchmarks are fixed in rock but there is none at this site).  We sink two sections and decide that is enough to hold the benchmark in place for the two months that it will be in use (for a permanent benchmark the rod is driven until it can go no further).  The brass cap is then stamped with a name (SPIT) and date (2005) and affixed to the top of the rod.  We are now able to set up the second station. The receiver will follow the same collection pattern: collecting signals for six hours, resting for twenty-four hours, and collecting for another six hours.

At the end of the collection period, the data from the sensors will be uploaded to an onboard computer and transmitted to the National Geodetic Survey in Washington D.C. where corrections to account for error introduced by things such as the atmosphere are applied. The corrected data, returned to the ship, will establish very accurately (within cm) the latitude and longitude for the site.  One final correction is made to the data before the site can be used. This error source is the satellite itself and comes from the satellite’s perceived position (where it thinks it is in the sky) as compared to its actual position.  The precise location is monitored by the United States Air Force.  Final corrections using this information will provide pinpoint accuracy (within mm) of the benchmark’s location. A temporary, or “fly-away”, DGPS station can now be placed at this benchmark and transmit signals easily received by the launches.

Personal Log 

Yet another beautiful day! Once on shore the mosquitoes were terrible – swarming in clouds around our heads.  A little bug dope, the warm sun, and cool breeze soon took care of this problem.  A great day to be out working!

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Mike Laird, July 28, 2005

NOAA Teacher at Sea
Mike Laird
Onboard NOAA Ship Rainier
July 24 – August 13, 2005

Mission: Hydrographic Survey
Geographical Area: North Pacific
Date: July 28, 2005

Weather Data

Latitude: 55°37.1̍ N
Longitude: 156˚46.6 ̍ W
Visibility: 10 nautical miles (nm)
Wind Direction: 140˚
Wind Speed: 5 kts
Sea Wave Height: 0-1΄
Swell Wave Height: 2΄
Sea Water Temperature: 12.2˚ C
Sea Level Pressure: 1009.8 mb
Cloud Cover: Stratus

Science and Technology Log 

Another beautiful day in the Gulf of Alaska – partially cloudy with lots of sun!  Today I remained aboard the RAINIER and had an opportunity to talk with Ensign Olivia Hauser about the map sheets.  The sheets are prepared to guide the launches on their echo sounding runs. The whole area to be mapped on this leg of the mission is subdivided into zones called sheets.  At the beginning of the workday, each launch is assigned a sheet for the crew to follow for that day. However prior to distribution to the launch crews, the sheets must be developed.

Each sheet (there are six sheets for our current assignment) is the responsibility of a single sheet manager who takes care of the initial preparation of the sheet, sheet revisions, and the beginning phases of data analysis.  In developing the sheet, the manager attempts to achieve 100% coverage of the seafloor.  This means that the manager attempts to determine the optimum distance between the lines the launch will follow during its sounding runs. In areas like the waters around Mitrofania where there is little or no existing data, the first run of a sheet is a best guess plot.  In essence, the launches are conducting reconnaissance runs.

The data collected during these runs, may reveal some error in the initial line plots.  One problem is called a “holiday” which is a gap between the lines (unsounded seafloor).  This happens when the lines are spaced too far apart for the depth of the water (the water is shallower than expected), and the footprint scanned becomes too narrow leaving a gap between it and the footprint of the neighboring line(s).  A second type of problem is excessive noise in the scan results. In reconnaissance work, this is often the result of a greater than expected water depth in a launch not equipped to handle soundings at that depth. When these types of errors are identified, the sheet manager will revise the sheet plotting a new set of lines to be run. If necessary, a different launch (one with appropriate echo sounding equipment) will be assigned to run the new lines.  Once a complete set of good lines is established for a sheet and seafloor data for the entire sheet is collected, initial analysis begins. Computer programs take cast data (conductivity, pressure, and temperature), tide information, GPS readings (corrected for error), data accounting for the pitch and roll of the launch and process the soundings.  The result is a first look at the bottom!  Subtle changes in shading reveal changes in floor depth and other bottom features. The soundings run by the RA5 launch so far have indicated a mostly flat floor with a few rock outcroppings and small ridges.

Personal Log 

The day was fantastic warm and sunny!  One of the crew caught a halibut, which the galley cooked–a special treat for dinner tonight!

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Tamil Maldonado, July 27, 2005

NOAA Teacher at Sea
Tamil Maldonado
Onboard NOAA Ship Fairweather
July 18 – 28, 2005

Mission: Hydrographic Survey
Geographical Area: North Pacific
Date: July 27, 2005

Science and Technology Log

During the day I talked with the captain about boat stability.  Stability is defined as the ability of a vessel to return to its original condition or position after it has been disturbed by an outside force. Anyone who has been at sea and felt the vessel roll, for example, and then right itself (only to roll in the opposite direction and right itself again) has seen stability in action.

Outside forces include wind seas, adding/removing weight, and free surface.  The six Motions of a Vessel in waves are rolling, pitching, yawing, heaving, swaying, and surging. Rolling is the motion about the vessel’s longitudinal axis.  Pitching is the motion about the vessel’s transverse axis.  Yawing is the motion about the vessel’s vertical axis.  Heaving is the vertical bodily motion of the vessel (whole vessel moves up and down together). Swaying is lateral (side to side) bodily motion.  Surging is the longitudinal (fore and aft) bodily motion.  All or most of the motions can occur simultaneously and have their effect on the efficient operation of a vessel.  While the ship’s officer cannot completely control these motions, there is much that can be done to diminish or alleviate their effects.

Motions of the Vessel and Governing Stabilities include:  Roll- Transverse Stability, Pitch- Longitudinal Stability, Yaw- Directional Stability, Heave – Positional Motion Stability, Surge – Stability in motion Ahead or Astern, Sway – Lateral Motion Stability. The way a vessel rolls is a direct indication of her stability.

The condition of a vessel is determined almost solely by the location of two points: the Center of Gravity (G) and the Center of Buoyancy (B).  G is the point at which all vertically downward forces of the vessel can be considered to act.  In other words, the ship will behave as though all of its weight were acting downward through this point.  B is the point at which all the vertically upward forces of support (buoyancy) can be considered to act, or, the center of volume of the underwater portion of the vessel.  In other words, the ship will behave as if all of its support is acting up through this point. There are a lot of mathematical concepts and processes to compute stability.  Theory of Moments, Inclining formula, Trigonometry, Change in Mean Draft are also implied in vessel stability.

During the afternoon I worked on the computer, and I put all my pictures on the FAIRWEATHER’s computer network.

We also had the drills: 1) Men on Board, 2)  Abandon Ship, and 3) Fire and Emergency.

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Tamil Maldonado, July 26, 2005

NOAA Teacher at Sea
Tamil Maldonado
Onboard NOAA Ship Fairweather
July 18 – 28, 2005

Mission: Hydrographic/FOCI Survey
Geographical Area: North Pacific
Date: July 26, 2005

Science and Technology Log

We are underway in the Gulf of Alaska, Southeast of Sitkinak Island.  This is our last day of doing FOCI survey. We used the Bongo Tow and CTD throughout day.

At 5:00 p.m. we were done with survey and transiting to Dutch Harbor, AK

At night I interviewed Chief Scientist, Janet Duffy-Anderson, one more time.  We talked about how to know fish ages and how fast they are growing.  It is because of their rings— the number of rings a larvae has will give the days they are alive.  Also, you can know their age by how far apart those rings are, which gives you the information of how fast they are growing.

Furthermore we talked about atmospheric changes and how this is affecting the ecosystem.  The target of FOCI is to get biological as well as physical data on the changes in the ocean and how those changes interact with the biota.  They wanted to do this research in Alaska because you can see changes more rapidly at the poles of the planet. We have seen phenomena like El Nino, La Nina and others increasing in frequency and duration. The rate between phenomena is increasing—they are happening  more frequently for the last decade.

I will be able to get fisheries raw data in time series done by FOCI and will continue doing some research back home in this area.

At night we did an acoustic hydrographic survey, and by changing depth target we got different data, all related. Changing the depth target changes how deep the beams go through the water and come back.  We worked with Hips & Sips Computer Software.  This program also corrects in real time the error estimates for each contributing sensor.  These entries are necessary for the computation of the Total Propagated Error.  The Vessel Configuration File (VCF) contains information about the different sensors installed on the survey vessel and their relationship to each other.  The information in the file is applied to logged, converted data files, and when the final sounding positions are calculated, the data is merged.  The entries in the VCF are time tagged and multiple time tags can be defined for each sensor.  This allows the user to update sensor information during the course of a survey.  This may occur if a piece of equipment has been moved.

In order to define the new fields in the VCF it is essential to understand standard deviation. The standard deviation is a statistic that explains how tightly various examples are clustered around the mean in a set of data.  When the data is tightly bunched together the bell-shaped curve is steep and the standard deviation is small.  When the data is spread apart, the bell curve is relatively flat indicating a larger standard deviation.

The vessel information will be displayed in the Vessel Editor.  The sensor positions are represented by colored dots. The VCF can be updated if a sensor changes position, and a unique time stamp ensures that the correct offsets are applied to data recorded at a certain time.  Each time the sensor information is changed, the drop down list above the 3-D vessel model will be updated to include the new time stamps.  The data grid below the 3D vessel contains all the offset information for the vessel.

Tomorrow… we will talk about the stability of the ship, and how its is done (so we do not sink!).