Coast Survey participates in international Arctic survey project – Part 2   1 comment

By Edward Owens

In a previous post, Edward shared his initial experience on board the Canadian Coast Guard vessel Louis S. St-Laurent as they traveled from Halifax, Canada, toward Tromsø, Norway. Today, he provides an update as well as a look at some of the features they found on the seafloor along the way.

photo of Edward Owens

Edward Owens on board Canadian Coast Guard vessel Louis S. St-Laurent.

It is a Sunday and our transit across the Atlantic on board Canadian Coast Guard vessel Louis S. St-Laurent  is nearly complete. We’ll arrive in Tromsø, Norway, on Tuesday morning where we’ll rendezvous with a pilot boat to complete the final leg of our internationally coordinated hydrographic mission, as the latest contribution to the Galway Statement on Atlantic Ocean Cooperation.

Shortly after leaving Newfoundland, our communications capabilities dropped out and the science team began to coordinate the continual logging and processing of the hydrographic data. With a few minor tweaks, our deep-water EM122 multibeam and Knudsen 3260 sub-bottom systems were acquiring excellent data. Our route to Norway has been fairly direct, but modified in a few places of interest such as the mid-Atlantic Ridge zone, to junction existing multibeam data in the area and to develop curious features derived from satellite derived bathymetry. The weather has cooperated for us quite well and we have only experienced some patches of fog and a single 24 hour storm event. This event was more like a gail, however, where the winds were 50 to 55 knots and the seas about 6 to 8 meters, enough to put spray over the wheel house and for Neptune to assure us we were fast approaching the Arctic Circle crossing.


The “Atlantic Heart” found on the western mid-Atlantic ridge.

During our transit along and over the mid-Atlantic ridge the echosounders portrayed a dynamic seafloor of uneven terrain, gorges, trenches, ridges, and peaks. Of greatest interest to the team were a handful of small volcano-like seamounts ranging from 100 to 300 meters proud of the seabed and from 500 to 1500 meters across, all in over 2,000 meter depth range. The two most significant of these have been tentatively named  the “Atlantic Heart” and the “Egg Cup”.

There is plenty of data to describe the area’s geological past. This section of seabed, and the ridge in general, forms part of the fault line that separates the European and North American tectonic plates and is being slowly formed by seafloor spreading. The two plates are moving apart by about 2 to 5 millimeters a year and as they do, molten magma from beneath the Earth’s crust seeps through the cracks from far beneath the surface which becomes lava and then cools and solidifies to form new seabed.

This process forms the ridge and all its visible scars, and it is in this area where we find the most dramatic seabed. These areas of uneven terrain are often the best places to find biogenic reefs and deep-water faunal communities. Many species of fish, coral, starfish, crab, and plenty of worms have been found living in association with these areas and aggregate to form nurseries and colonies. In this way, seabed mapping can begin to locate these communities which can then be managed effectively and conserved accordingly.


The “Egg Cup” found on the eastern mid-Atlantic ridge.

The Captain and crew are as fine as you could ever hope to sail with. There have been numerous social events and gatherings to get to know each other and share stories, along with the extremely important events surrounding the right of passage for all those, myself included, to graduate from a “pollywog” to a “shellback” if one can prove themselves worthy and of strong enough will to pass challenges and humiliation that Neptune demands in order to be accepted into his Northern realm of the Arctic Circle.

I will leave blank the details surrounding this rite of passage for all those who may experience this ceremonial affair. I will, however, leave you knowing I am now a loyal subject of this realm as dictated by my certificate from the Captain to alert all narwhals, walrus, and creatures of the sea that my sacrifices and suffering were sufficient to merit this honor.

Posted August 5, 2015 by NOAA Office of Coast Survey in Nautical charts

Coast Survey hosts Hollings Scholar   2 comments

Valerie in the NOAA Ship Fairweather engine room.

Valerie Rennoll, Coast Survey’s first Hollings Scholar, stands in the NOAA Ship Fairweather engine room.

By, Melissa Volkert

Meet Valerie Rennoll, the Office of Coast Survey’s first Ernest F. Hollings (Hollings) Scholar on a NOAA vessel.

Originally from Glen Rock, Pennsylvania, Valerie discovered the Hollings Scholarship from a professor at American University while working toward her double major in physics and audio technology. She found that the scholarship program aligned well with her interests as she learned of NOAA’s extensive work with underwater acoustics.

“I was excited by the idea of exploring applications of underwater acoustics and decided to submit an application,” explains Valerie.

For the first six weeks of her internship, Valerie was based in Silver Spring, Maryland, where she investigated the use of data from outside sources to evaluate Coast Survey’s nautical charts. Coast Survey aims to make the best use of the large amount of data received from outside sources in the most responsible way possible.

The data Valerie processed and analyzed was from U.S. Coast Guard Cutter Healy. The Healy has been transiting the Bering Strait, Valerie’s targeted area, for the past ten years. Although the Healy was in the area for other reasons, depth data was also collected during that time.

Map of Healy track line data.

The Healy track line data, displayed in green on the Bering Sea nautical chart, is the data Valerie analyzed for her project.

Using a general workflow that she created, Valerie processed the data and compared it to charted data. She focused on areas that showed a disagreement greater than ten meters in depth. Valerie prepared a descriptive report summary to the Hydrographic Surveys Division describing these areas and recommended updates.

For the following three weeks of her internship with Coast Survey, Valerie was on board NOAA Ship Fairweather, continuing her initial project while also receiving training in traditional hydrographic surveying. The Fairweather was transiting Valerie’s targeted area of the Bering Strait. In fact, she used information collected by the Fairweather to compare to the Healy data. With this, her internship was all-encompassing—she was able to experience the analysis as well as the collection of depth data.

“My favorite part of the internship was going on board NOAA Ship Fairweather. The whole crew was so welcoming and I was really able to delve into learning about hydrography. I was also lucky enough to earn my Blue Nose Certificate for crossing the Arctic Circle and the Golden Dragon certificate for crossing the International Date Line. The whole experience was truly a once-in-a-lifetime opportunity,” said Valerie.

NOAA’s Hollings Scholarship program provides support for undergraduate student training in NOAA mission sciences, teacher education, environmental literacy,  and helps prepare students for public service careers within NOAA and other science agencies. This is the first time Coast Survey has had the honor of hosting a Hollings Scholar for a summer internship.

Valerie on board NOAA Ship Fairweather departing Dutch Harbor, Alaska.

Valerie on board NOAA Ship Fairweather departing Dutch Harbor, Alaska.

Valerie taking a CTD (Conductivity, Temperature, and Depth) cast to measure sound speed in the water.

Valerie taking a CTD (Conductivity, Temperature, and Depth) cast to measure sound speed in the water.

Posted August 3, 2015 by NOAA Office of Coast Survey in Nautical charts

What does the age of the survey mean for nautical charts?   2 comments

Alaska’s nautical charts need to be updated — we all know that. The diagram below shows the vintage of survey data currently used for today’s charts in Alaska. The graphic includes all surveys done by NOAA’s Office of Coast Survey (and its predecessors), and some limited data acquired by other agencies, i.e., the U.S. Coast Guard. Areas that are not colored in have never been surveyed or have data acquired by another source — from Russia or Japan, for instance — before the U.S. was responsible for charting in that area.

Vintage of Alaska survey

What are the differences between data collected in 1900, 1940, or 1960? Let’s take a look at a…

Brief Historical Sketch of Survey Technologies

Nautical charts have a lot of information, but mariners especially are concerned with two major components: water depths (known as “soundings”) and obstructions (like underwater seamounts or wrecks).

Different eras used different technologies to find, measure, and determine the position of the two components. Note that adoption of new systems does not happen abruptly; rather, new technologies are phased in as techniques and equipment improves.

Measuring Water Depth (Soundings)

3.7 million years ago to present day: sounding pole

It isn’t inconceivable that the earliest humanoid, Australopithecus afarensis, used sticks to gauge water depths before crossing streams and rivers. People still do it today.

Egyptian use of sounding pole

Note the ancient Egyptian on the far right, using a sounding pole.

~ 2000 B.C. to 1930s: lead line

As good as they were for their eras, 19th and 20th century surveyors faced technological challenges. The first challenge was accounting for gaps between depth measurements. The second was the inability to be totally accurate in noting the position of the measurement. (In other words, a specific location out in the ocean may be 50 feet deep, but a surveyor must also accurately note the position of that specific location.)

Casting a lead line

This surveyor is casting a lead line.

Early Coast Survey hydrographers measured depths by lead lines — ropes with lead on one end — that were lowered into the water and read manually. Even though soundings were generally accurate, coverage between single soundings was lacking. And we need to remember that this was before the age of GPS. While sextants gave accurate positions when a hydrographer could fix on a shoreline feature, the further offshore the survey, the less accurate the position.

(Interesting fact: Hydrographers still use lead lines occasionally, in some circumstances — but not for a complete survey.)

There have been variations on lead lines through the centuries. From 1492 to the late 1870s, for instance, mariners used hemp rope for deep-sea soundings.

(Interesting fact: Christopher Columbus and Ferdinand Magellan each tried to measure mid-ocean depths with about 1,200 feet of hemp rope. Neither one of them found the sea bottom.)

In 1872, the hemp was replaced by small diameter piano wire (again, primarily for deep-sea work), and the weight of the lead was increased. Later, hydrographers added a motorized drum to wind and unwind the line, with a dial to record the length of the line.

(Interesting fact: In 1950, the British ship Challenger used piano wire in the first sounding that established Mariana Trench as the deepest place on earth.)

20th century to the present: echo sounders

comparison of survey technique coverage

Compare the bottom coverage achieved by the different survey methods.

1918 to 1990s: single beam echo sounder

Sonar came into its own in 1913. The first echo sounders (also known as “fathometers”) had single beams that measured the distance of the sea floor directly below a vessel. The echo sounders were able to take many more depth measurements than was possible with the lead line, but the technique still resulted in gaps between the lines where the beam measured the water depth.

The U.S. Coast and Geodetic Survey (a NOAA predecessor agency) adopted this acoustic sounding technique in 1923, installing it on USCGS Ship Guide. But full-fledged change didn’t happen right away. These early sounding systems were too large to install on survey launches used in harbor and inshore work, so from 1924 until the early 1940s many surveys were still conducted with a lead line, and many were totally acoustic — and some were hybrid, using soundings from both methods, depending on coverage area and seafloor configuration.

→ 1940: U.S. Coast and Geodetic Survey fully adopts single beam echo sounding technology

The development of smaller “portable” fathometers for shallow waters, about 1940, was a primary impetus in the obsolescence of lead line as survey technology and the adoption of acoustic systems. The development of World War II electronic navigation systems for bombing purposes led to the development in 1945 of the first survey-quality electronic navigation systems, which allowed for more accuracy in positioning.

1964 to current day: multibeam echo sounder

By mid-century, scientists were increasing the beams projected by the echo sounder, to get a broader swath of measurements. The multibeam echo sounder was developed for the Navy in 1964, but it remained secret until the late 1970s when commercially available systems were developed.

Coast Survey first used a MBES technique, called the “Bathymetric Swath Survey System,” in 1977 on NOAA Ship Davidson, for depths ranging from 160 to 2,000 feet. In 1980, NOAA Ship Surveyor installed a deep-water MBES system called “Sea Beam,” for depths from 1,600 to 33,000 feet.

About 1986, Coast Survey began using GPS to calibrate medium-frequency navigation systems while operating in the far reaches of the United States Exclusive Economic Zone. By the mid-1990s, GPS was the primary control for accurate positioning.

→ 2000: Coast Survey fully adopts multibeam surveying

By 2000, Coast Survey was performing full-coverage multibeam hydrographic surveys for charting purposes. NOAA survey ships now use multibeam echo sounders that measure navigable coastal depths from 45 to 1,000 feet. For shallower and more constricted waters, the ships deploy hydrographic survey launches with multibeam echo sounders that efficiently and safely survey areas from 12 to 200 feet deep. These systems make it possible to acquire 100% sea floor coverage in the survey grounds (excluding ultra-shallow, near-shore, or obstruction areas).

Finding Underwater Obstructions

1880s to early 1990s: wire drag

Surveyors used wire drag, not as a sounding system but as a way to look between the sounding lines to find obstructions to navigation and establish safe navigational channels. The first documented wire drag was conducted in the 1880s, in French Indochina, Gulf of Tonkin area, attaching the wire to buoys at each end and letting it drift with tidal currents.

Around 1900, the U. S. Lake Survey developed the technique of using a ¼-mile wire drag between two boats. In 1903, Coast Survey began using the technique, and within a few years was using it extensively in Alaskan waters as they looked for pinnacle rocks. Coast Survey’s Alaska wire drags were up to 3.5 miles long. (Initially, “least depths” over discovered obstructions were determined by lead line, then acoustic means and, ultimately, by divers with depth/pressure gauges.)

wire drag operations

Survey vessels conduct wire drag operations.

1960 to present day: side scan sonar

Side scan sonar is essentially the sonar equivalent of an aerial photograph. It improves the ability to identify submerged wrecks and obstructions. Evolving from submarine detection sonars of World War I and World War II, side scan sonar was fairly well developed by 1960, when the United Kingdom Hydrographic Office started using it regularly with their surveys.

→ 1990: Coast Survey fully adopts side scan sonar for East Coast and Gulf Coast surveys

NOAA Ship Whiting used the technology in 1984-1985 for approaches to New York. U.S. Coast Survey fully adopted side scan sonar (in place of wire drag) in the early 1990s.

lowering the tow fish for SSS

Side scan sonar operations use “towfish” like this one, lowered into the water and towed from the back of the vessel.

SSS image of wreck

Side scan sonar captures images of objects, which improves the ability to identify submerged objects.

Today’s Charts Reflect Different Tech Eras

Each of NOAA’s 1000-plus nautical charts, even today, can contain information collected by any or all of these sounding and positioning techniques.

Most nautical charts are an amalgamation of geospatial information collected using different techniques at different times. For example, one area of a specific current-day nautical chart might be based on a lead line and sextant survey conducted in 1910, and another area on the same chart might be based on a multibeam and GPS survey conducted in 2010. If we dig deep enough, we will probably find a sounding or two from the 18th century British explorer, Captain James Cook.

NOAA cartographers mold this disparate information so that it fits together as a coherent representation of the geographic area.

So when was the data acquired for the chart you’re using? NOAA cartographers add a “source diagram” to large-scale charts. (See the diagram on the current chart 16240, pictured below.) Check yours. That will give you the years of the surveys… and now you have a better idea on the technology used by the surveyor.

source diagram 16240

This is the source diagram on nautical chart 16240.

Coast Survey participates in international Arctic survey project   1 comment

By Edward Owens

Edward Owens

Coast Survey’s Edward Owens on the Canadian Coast Guard vessel Louis S. St.-Laurent  as it approaches The Narrows near the city of St. John’s.

Hello to all from the Canadian Coast Guard vessel Louis S. St-Laurent (CCG LSSL), affectionately called the ‘Louis.’ She is an impressive 120 m long, 24.5 m wide with a cruising range of 23,000 nautical miles and carries two CCG helicopters. There are 86 cabins with 100 bunks and today she currently sails with 77 souls on board. I’ve gotten lost, turned around, and confused while navigating my way through the labyrinth of neat and tidy stairways, corridors, and doorways on numerous occasions. Luckily, I’m beginning to find my way around thanks to all the artwork and placards mounted on the walls which I’ve depended on as landmarks to help me get where I’m going. Everything is arranged on five main decks. I am berthed on the 300 level or the flight and boat deck conveniently near the acoustics science lab. The galley is three decks down and as long as I can find it, I’ll be just grand.

Today is Monday, the 27 of July, and it is 08:40 UTC (ship’s time), 06:10 St. John’s time (we are just off the Newfoundland coast), and 05:40 along the U.S. East Coast. Sunday afternoon we made a short stop at The Narrows, the entrance to Newfoundland’s city of St. John’s. There was a slight wind and low sky with temperatures in the refreshing low 50°’s F. The fast boat was deployed to make a few runs to the harbor to collect additional personnel waiting to join the ship along with many parcels and packages that made their way on board before we set off on the main leg of our journey. As a good omen, numerous species of whales fed, frolicked, and spouted into the cool air about the ship bidding us on our way.

We had left Halifax, Nova Scotia, on Friday from Canada’s impressive Bedford Institute of Oceanography, which sits nestled in the Bedford basin at the rear of Halifax harbor. Outside, the Coast Guard maintains a number of multi-purpose research vessels. I have been invited aboard on the first leg (Halifax – Tromsø, Norway) of a four-month Arctic voyage as part of an international scientific collaboration between Europe, Canada, and the U.S. to begin the long and complex task of mapping the seabed of the North Atlantic Ocean. The survey is the second to be launched by the alliance, formed in May 2013, following the Galway Statement on Atlantic Ocean Cooperation (named such for the location of the documents signing in Ireland). The three signatories agreed to jointly undertake the challenge to better understand the North Atlantic Ocean, and to promote the sustainable management of its resources.

Canadian Coast Guard Ship

Canadian Coast Guard vessel Louis S. St.-Laurent, host of the four month Arctic voyage as part of an international scientific collaboration between Europe, Canada, and the U.S.

The first survey under these auspices was led by the INFOMAR team (integrated mapping for the sustainable development of Ireland’s marine resource) on the R. V. Celtic Explorer who were joined by representatives of each of the signatories of the Galway Statement: the Marine Institute (Canada), the National Oceanic and Atmospheric Administration (U.S.), and Portuguese Sea and Atmosphere Institute (Portugal) and Marine Institute (Ireland) representing the European Union. The international team transited from St. John’s, Newfoundland to Galway in June 2015.

The second survey is hosted in July by the Canadian Government aboard the Louis as we transit from Halifax to Tromsø in Norway. The team is led by Paola Travaglini of the Canadian Hydrographic Service (CHS) with Shauna Neary (CHS), Dave Levy (CHS), Kirk Regular (Fisheries and Marine Institute of Memorial University, Newfoundland), David O’Sullivan (Ireland’s Marine Institute and INFOMAR), and myself, Edward Owens, representing NOAA. The team is highly experienced and extremely enthusiastic about the mission at hand and the chance to collaborate with their international colleagues; speaking for myself, it’s an opportunity that is not only exciting but the outcomes are hugely beneficial to build relations, learn, and succeed with our partners as we cooperate in this effort. After the survey mission to Tromsø is complete (hopefully on August 4) the Louis will continue into the high Arctic after the international team departs and will re-enter Canadian waters in November via the Northwest Passage after sailing to the North Pole. Incidentally, the Louis was one of two surface vessels that were the first to cross the Arctic Ocean via the geographical North Pole in 1994. I find after a taste of the open ocean, the prospect of making another of these crossings tempts me as we are heading into the deep water for this transit north.

Computer screen showing route from Newfoundland, Canada, to Glaway, Norway.

Route the Canadian Coast Guard vessel Louis S. St.-Laurent will be taking during its second survey mission from Halifax, Canada, to Tromsø, Norway.

The journey until now has been relatively uneventful as the team orientates itself and begins to acclimate to a daily survey routine. As we make our way off the Nova Scotian shelf, where ocean depths are not much greater than 200 meters deep, the sonar depths decline gradually down the Orphan Knoll Slump and into thousands of meters of ocean water. We are operating an EM122 multibeam echo sounder which sends and receives acoustic signals to/from the seabed giving accurate depth readings and also an indication of seafloor type.  Additionally, we are logging sub-bottom and mid-water bathymetry data to take full advantage of this crossing and provide data to a larger audience in the scientific and commercial community.  The EM122 is a deep-water echo sounder and will really come into its own in deeper waters off the edge of the shelf and return detailed, high-resolution imagery of the seabed. Here we expect to chart the deep ocean waters of the Atlantic Basin and up and over the Mid-Atlantic Ridge.

During the cruise I intend to describe life aboard a Canadian Coast Guard vessel and share the thoughts of the officers and the crew of the Louis as it crosses into the Arctic Circle. There is a strong community spirit already evident. A ship’s announcement has just said there is a ‘ceremony’ later for those who have never crossed into the Arctic Circle before…stories of reverse Mohawk haircuts and the like abound. There are nine new CCG cadets on board, so hopefully they’ll attract the most attention, but for once I’m quite content to be in the left lane on the freeway to baldness already! I’ll try and report on what could be dangerously interpreted as a kind of initiation of sorts…

…farewell from the Louis for now…

International team on Canadian Coast Guard Vessel.

The international team about to embark on the second leg of the Arctic survey mission, Kirk Regular (Fisheries and Marine Institute of Memorial University, Newfoundland), David O’Sullivan (Ireland’s Marine Institute and INFOMAR), Dave Levy (CHS), Edward Owens (NOAA), Shauna Neary (CHS), and Paola Travaglini (CHS).

Posted July 28, 2015 by NOAA Office of Coast Survey in Nautical charts

NOAA holds international workshop for nautical chart agencies   2 comments

Workshop participants.

Hydrographers from 11 different countries attended a workshop on nautical chart adequacy in Silver Spring, Maryland.

This week, hydrographers from 11 different countries traveled to Silver Spring, Maryland, to attend a workshop on nautical chart adequacy. Workshop participants included scholar students from the General Bathymetric Chart of the Oceans Organization, and participants from Israel, Malaysia, South Korea and United Kingdom. The workshop, developed and hosted by Coast Survey and the Joint Hydrographic Center, University of New Hampshire, trained the hydrographers on procedures to assess the adequacy of their respective nautical charts using publicly-available information.

This workshop was developed in part to address the International Hydrographic Office C-55 publication recognizing the need to improve the collection, quality, and availability of hydrographic data world-wide. Evaluating the adequacy of charts can be challenging to many national hydrographic offices given the lack of reliable vessel traffic data and minimal resources to survey and assess the changing nature of the seafloor and shoreline.

During the workshop trainers incorporated the latest techniques, using data from the maritime automatic identification system (AIS) that displays actual vessel traffic, as well as depth measurements deduced from satellite images. The Silver Spring workshop is the first of several U.S.-planned training activities that will facilitate a global standardized procedure for assessing the adequacy of nautical charts used by mariners around the world.

Students at computers.

Dr. Shachak Pe’eri, from the University of New Hampshire’s Joint Hydrographic Center, assists Limor Gur-Arie from Israel, during the nautical chart adequacy workshop.

Instructor demonstrating use of publicly available information.

Lt.j.g. Anthony Klemm, from Coast Survey’s Marine Chart Division, provides a demonstration on the use of marine automatic identification system (AIS) data in determining nautical chart adequacy.

Posted July 16, 2015 by NOAA Office of Coast Survey in Nautical charts

Coast Survey attends first meeting of IHO’s Nautical Information Provisions Working Group   Leave a comment

Coast Survey attended the first meeting of the Nautical Information Provisions Working Group (NIPWG) held at the International Hydrographic Organization in Monaco.

During the meeting, Coast Survey’s Tom Loeper, chief of Navigation Services Division’s Coast Pilot branch and Great Lakes navigation manager, was reappointed as the secretary for the working group, a position he has held for 2 years. Two other working group members from the United States also attended the meeting, Briana Sullivan from the University of New Hampshire, and Mike Kushla from the National Geospatial-Intelligence Agency.

While in Monaco, the NIPWG had the opportunity to visit the training ship Kojima of Japan Coast Guard moored at Port Hercule in Monaco Harbor. While onboard the Kojima, Robert Ward, President of the IHO, spoke about the importance of hydrography worldwide and of the long relationship between the IHO and the Grimaldi family of Monaco, dating back nearly 100 years. Representing the Grimaldi family at the event was His Serene Highness Prince Albert of Monaco. To conclude the ceremony, crew members of the Kojima demonstrated a mock sword fight and the traditional method of making rice cakes.

NIPWG meets regularly to develop and maintain guidance, standards, and other supplemental information for charts, much like U.S. Coast Pilot.  This information is typically presented as an overlay for electronic navigational charts and are often used for voyage planning by the mariner.

Formerly the Standardization of Nautical Publications Working Group, NIPWG was established by the Hydrographic Services and Standards Committee as part of a restructuring effort to change its focus from paper-based to digital products and services.

His Serene Highness Prince Albert of Monaco and Captain Tetsushi Mitsuya, commanding officer of the training ship Kojima of Japan Coast Guard, stand alongside Robert Ward, President of the IHO, during his remarks on board the Kojima

His Serene Highness Prince Albert of Monaco and Captain Tetsushi Mitsuya, commanding officer of the training ship Kojima of Japan Coast Guard, stand alongside Robert Ward, President of the IHO, during his remarks onboard the Kojima.

Crew members of the training ship Kojima of Japan Coast Guard demonstrate a traditional method of making rice cakes during the event on board the Kojima

Crew members of the training ship Kojima of Japan Coast Guard demonstrate a traditional method of making rice cakes.

Coast Survey’s Tom Loeper and Captain Tetsushi Mitsuya, commanding officer of the training ship Kojima of Japan Coast Guard, attend the IHO event onboard the Kojima.

Coast Survey’s Tom Loeper and Captain Tetsushi Mitsuya, commanding officer of the training ship Kojima of Japan Coast Guard, attend the IHO event onboard the Kojima.

Posted July 8, 2015 by NOAA Office of Coast Survey in Nautical charts

Coast Survey aids U.S. Coast Guard in recovering sunken buoy   Leave a comment

Coast Survey’s Navigation Response Team (NRT) 6 responded to a request from the U.S. Coast Guard to locate and facilitate recovery of a sunken mooring buoy near Sausalito, California.

Although not a threat to surface navigation, there are two reasons for this recovery effort. The first is to protect mariners from getting their anchors caught on the buoy or tangled in the mooring chain. Recovery will also allow the U.S. Coast Guard to repair and possibly reuse the buoy.

A mooring buoy is an anchored buoy fitted to receive a ship’s mooring chain. It essentially allows mariners to secure their ships without the use of an anchor. The lost mooring buoy is four feet in diameter connected to a chain 117 feet in length.

Using sonar, NRT6 created a ten centimeter resolution grid (a network of horizontal and vertical lines superimposed over a chart) and located five features on the seafloor that could be the lost mooring buoy.

This is a chartlet showing the location as well as measurements of the five different features found through multibeam sonar surveys of the NRT6.

Chartlet showing the locations and measurements of five features found through multibeam sonar surveys of the NRT6. These five features are potentially the lost mooring buoy.

The first feature is the strongest candidate. Its length, width, and height appear similar to that of the lost buoy and there is a notable lack of scouring. Scouring occurs when swift moving water flows over submerged objects over time. The lack of scouring on feature one indicates that it has not been underwater for long.

This is a chartlet showing images and information about feature one

Chartlet displaying feature one, the feature most likely to be the lost mooring buoy.

Features two and three appear to be the two buoy blocks that are square in nature and and have established scouring. Feature three also has what appears to be a mound of rubble resting next to it which is thought to be a mooring chain. Features four and five are merely curiosities that are being considered. The following video tour further illustrates and explains these five features.

Although we have not yet concluded which (if any) of the five features is the lost buoy, the U.S. Coast Guard has recovery operations planned for July 1st. We will then know for sure if NRT6 indeed located the lost buoy.

UPDATE (July 9, 2015)

The U.S. Coast Guard Ship Aspen successfully recovered the sunken Sausalito mooring buoy last week. They were able to hook onto the chain on the second attempt with the aid of NRT6’s images.

“Knowing exactly where to drag our grappling hook really helped, and made what could have been a day-long, frustrating, and risky evolution relatively quick and painless,” said LTJG Sarah Jane Sapiano, Aspen operations officer.

U.S. Coast Guard Ship Aspen successfully recovers lost mooring buoy.

U.S. Coast Guard Ship Aspen successfully recovers lost mooring buoy. Photo courtesy of U.S. Coast Guard

Posted June 24, 2015 by NOAA Office of Coast Survey in Nautical charts


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