Archive for the ‘Nautical charts’ Category

New autonomous surface vehicles to deliver shoaler depth measurements for NOAA nautical charts   4 comments

If you look closely at any U.S. coastal nautical chart, you’ll likely find that the areas closest to the shore, shoals, and rocks do not have updated depth measurements. In many areas, safety concerns prohibit the use of NOAA ships or launches to survey the shoalest depths. In many areas, the water is too murky to be mapped with the airborne lidar systems used in clear waters. Now, however, charting those shallow areas is about to get safer, thanks to recent purchases of small, commercial off-the-shelf, unmanned survey vessels.

This summer, NOAA Ship Thomas Jefferson will deploy a “Z-Boat,” offered by Teledyne Oceanscience out of Carlsbad, California.

Lt. Carrier deploys Z-Boat

Lt. Joseph Carrier, operations officer on NOAA Ship Thomas Jefferson, deploys a Z-Boat from the ship.

The Z-Boat complements the ship’s existing hydrographic toolkit.

  • Thomas Jefferson uses its multibeam echo sounder to measure depths from 45 to 1000 feet.
  • For shallower and more constricted waters, the ship’s two hydrographic survey launches with multibeam echo sounders efficiently and safely survey areas from 12 to 200 feet deep.
  • With the new Z-Boat (using a single beam echo sounder), Thomas Jefferson can measure depths in areas as shallow as one foot, and get that data into processing almost immediately. The boats are highly maneuverable, turning in their own 5.5-foot length, meaning they can get much closer to piers, pilings, and the shoreline than a full-sized launch.

This new capability is important to improving charts for smaller vessels operating near the coast, and in the inlets, bays, and harbors so critical to many small coastal towns. In the 1930s, the Roosevelt Administration – through its massive Depression-era public works program – hired hundreds of men to survey shallow Intracoastal Waterway areas. However, NOAA has done very little survey work in shallow water in the 80 years since then. Not surprisingly, there is a backlog of reported shoals, rocks, wrecks, and obstructions in shallow water, leading to an increased risk of grounding for those smaller vessels. Knowing the depth in these inlets is also important to accurately predicting coastal inundation during storms.

Thomas Jefferson, with the support of NOAA’s Office of Marine and Aviation Operations’ innovative platform program, plans to use two Z-Boats this summer in Massachusetts to investigate shoals and rocks in Buzzard’s Bay and Vineyard Sound. This December, they will use them in a project near Chesapeake Bay.

Doug Wood deploys Z-Boat

Doug Wood, physical scientist on NOAA Ship Thomas Jefferson, deploys a Z-Boat from the ship’s fantail.

“Coast Survey has been exploring the use of autonomous underwater vehicles – AUVs – to support nautical charting for over a decade,” explains Rear Admiral Gerd Glang, Coast Survey director. “Autonomous surface vehicle – ASV – technologies have advanced in recent years, and NOAA is now also exploring these for our hydrographic operations. The Z-Boat is one of several autonomous surface vehicles that we are experimenting with.”

Through a hydrographic survey contract with NOAA, TerraSond (Palmer, Alaska) is using an ASV in addition to their traditional manned boats. (See this article in Marine Technology News.)

One of the benefits of using off-the-shelf vehicles like Z-Boats is that hydrographers are able to calibrate the boats and put them into use quickly, without the need for additional installation and integration of a survey system. Thomas Jefferson took delivery of the boats on August 13. They now have qualified the system for hydrographic use, developed first-generation deployment and retrieval systems, and trained a cadre of Z-boat “pilots.”

“Two weeks from delivery to a calibrated system with trained operators is a significant achievement,” said Capt. Shepard Smith, Thomas Jefferson’s commanding officer. “We have already used them to conduct a small survey in Newport, Rhode Island, and we are thrilled with the new capability this boat will give us in our coastal projects.”

Thomas Jefferson will operate the boats from a control station on the ship or one of their launches. Depending on the circumstances, technicians have several options to control the boats, by using: 1) a handheld remote control; 2) a networked radio link with one-mile range; or 3) an onboard autonomy module. NOAA is working with Teledyne and with researchers at the University of New Hampshire-NOAA Joint Hydrography Center to develop improvements to the boat’s autonomy system that will permit it to gradually work more independently of the operator. With more Z-Boat autonomy, survey ships can operate a larger fleet of boats without adding additional operators.

ENS Head pilots Z-Boat

Ensign Marybeth Head pilots a Z-Boat in preparation for autonomous operations during training.

Capt. Richard T. Brennan, chief of the Coast Survey Development Laboratory, puts this move into a strategic technology context.

“NOAA envisions unmanned and autonomous systems working in conjunction with our manned systems, deployed and controlled from our hydrographic survey ships,” Brennan explained. “The Z-Boats are the first step towards unmanned surface vessels. We are looking forward to the lessons learned to drive further innovation in communications and automation technology.”

Thomas Jefferson will be exploring other options for the boats. For instance, Z-Boats have an onboard streaming video camera, so the operator can see what the boat “sees” in real-time, raising the possibility of additional uses beyond depth measurements. And although these Z-Boats are fitted with single beam echo sounders appropriate to very shallow water, there is an option to fit them with side scan sonar, or a multibeam system, for other applications.

“Deploying the Z-Boat from the Thomas Jefferson is a significant milestone for the NOAA fleet,” said Rear Admiral David Score, director of the Office of Marine and Aviation Operations. “In the coming decade, these types of unmanned systems will become the norm. We will be able to build on Thomas Jefferson’s experience in unmanned systems as we expand these programs into the broad range of scientific observations that the NOAA fleet provides.”

The ship is selecting the nicknames of the two Z-Boats. Go to the NOAA Ship Thomas Jefferson Facebook page, and see what names they are considering!

Hurricane Katrina: 10 Years Later   Leave a comment

Ten years ago this week, Hurricane Katrina devastated the Gulf Coast, affecting millions of lives. This disaster brought together all of Coast Survey’s capabilities on an unprecedented scale to help in response and recovery efforts in the storm’s aftermath. Ten years later, Coast Survey reflects back on the planning and response to Hurricane Katrina, and looks to their progress in developing tools to aid in coastal resilience.

Explore the story map.

image of story map

Hurricane Katrina: Ten Years Later
NOAA’s Office of Coast Survey looks back

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

Report from the Arctic: Surveying Kotzebue Sound 2015   Leave a comment

By Starla Robinson, project manager in Coast Survey’s Hydrographic Surveys Division

Two hundred years after Otto von Kotzebue and the crew of the Ruiric explored what would later be named Kotzebue Sound, NOAA ships Fairweather and Rainer follow in the same tradition. Two centuries ago they were searching for the Northwest Passage in support of trade. Today, we explore to improve the science and safety of navigation in support of commerce, environmental protection, and local communities. Our bathymetric data and observations will also be used to better inform coastal decision-making.

kotzebue-historical charts

Original chart of Kotzebue Sound (left). 1973 chart of Kotzebue Sound (right). Today’s chart of the project area is not significantly different from that of 1973.

Many things have changed since the crew of the Ruiric braved these waters. However, operations in the Arctic are still challenging. For much of the year Kotzebue Sound is frozen over. The remote location makes arriving and maintaining basic needs of the ships and crew difficult–just being here is a success.

Technology has made navigation safer and surveying more efficient. For example, rather than the discrete lead lines that were once used to obtain depth measurement data in this project area (which is about the size of Delaware), multibeam echo sounders acquire the same amount of data in just one square meter. For multibeam surveys, the speed of sound must be measured in the water column and the motion of the vessel must be recorded and corrected in the data. We use side scan sonar to produce imagery of the sea floor. GPS is used to triangulate our position rather than sailors taking bearings on shore stations. To better refine our precision, we construct horizontal and vertical control stations that must be operational before bathymetry data can even be collected.

It takes teamwork on and off the ship and NOAA has brought together many resources. Contractors are used to establish vertical control stations recording water levels. The Center for Operational Oceanographic Products and Services (CO-OPS) monitors the data and creates tide models. Subject matter experts in side scan sonar assist with the surveying effort. Teams on land plan and support the expedition and continue to process the data for the chart after the ships have left. Many things have to align to make our charting efforts a success.

On the ship, our exposed location limits survey activities.  The small boats for survey can only be deployed when the sea state is safe. Teams must brave the surf to maintain the control stations.  The crews of the Rainier and Fairweather work hard to take advantage of windows of good weather. They work long hours, in rough conditions, away from convenience and family, in pursuit of the chart. We are today’s explorers seeing the full picture of the seafloor for the first time.

Chart of Kotzebue Sound, AK, with bathymetric data.

NOAA survey progress map highlighting hydrographic survey coverage by NOAA ships Fairweather and Rainier as of August 17, 2015.

Coast Survey welcomes Guy Funnell from the UK Hydrographic Office   Leave a comment

Hydrographic offices around the world often share expertise and experiences in order to improve products and processes. In that vein, NOAA’s Office of Coast Survey welcomes Guy Funnell, a product manager from the United Kingdom Hydrographic Office who will be working with us in a unique employee exchange.

The exchange will be of immense benefit to Coast Survey, as we continue to explore practices and technologies to improve Coast Survey’s product management.

The UKHO is an equivalent to Coast Survey, but with some major differences. While Coast Survey and the UKHO have a working relationship going back over a century, the UKHO got a jump on us in chart production, producing their first chart (of Quiberon Bay in Brittany) in 1800. We came along a little later, when President Thomas Jefferson signed legislation in 1807, calling for a survey of the coast.

The two agencies have developed different nautical chart production and distribution processes.

The UKHO is a part of the Ministry of Defence, operating as a trading fund (a type of government department or agency).  It uses the revenue it makes to meet its outgoings, whereas Coast Survey’s funding comes from tax dollars so our products are free to the public. Another difference is in the collection of hydrographic data for application to Admiralty Charts. The UKHO does not have their own fleet of ships and survey equipment, and so they rely on the Royal Navy, the British Maritime and Coastguard Agency, and contractors for charting data; Coast Survey primarily uses NOAA ships and contractors. UKHO makes arrangements with other countries for their nautical charting data; we do not.

The two agencies have a lot to learn from each other. One of Funnell’s challenges will be to learn how the U.S. regulatory shipping environment compares to other parts of the world. For instance, he will look at our tier of federal, state, and local regulations, how the regulations are enforced, what impacts they have on operations, and how users comply and demonstrate that they comply, as well as how they are inspected. Guy also aims to understand the different operational factors for coastal and river traffic, how they compare to the UK, and how they serve the international mariner.

Funnell will also further his understanding of how NOAA operates. In particular, he will examine the integration of navigation products and services to other NOAA services, the collection of data from private or academic sources, our working relationships with ports and terminal operators, and customer feedback for new product development. As Coast Survey continues our move into digital products, synchronicity will also be an important area for exploration.

Upon his arrival in the U.S., one of Funnell’s first stops was in New Orleans, which is the largest complex of ports and the most congested waterway in the U.S. During an early morning, deep-draft ship transit up the Mississippi River to a terminal near Baton Rouge with New Orleans-Baton Rouge Pilots Association’s Jason Ledet, Funnell witnessed first-hand the importance of NOAA’s environmental digital/electronic data and charting resources.

Guy Funnell (standing) observes navigational challenges of the Mississippi River, with NOBRA pilot Jason Ledet.

Guy Funnell (standing) observes navigational challenges of the Mississippi River, with NOBRA pilot Jason Ledet.

Off the ship, Guy was in consultations and discussions with Louisiana chart agents and distributors of both Admiralty and NOAA products.

Guy Funnell (left) meets with NOAA-certified print-on-demand chart sub-agent Horizon Nautical.

Guy Funnell (left) meets with NOAA-certified print-on-demand chart sub-agent Horizon Nautical.

Guy Funnell’s stay in the U.S. will last until the end of September. Coast Survey’s Rachel Medley, the acting chief of Navigation Services Division’s Requirements and Products Management Branch, will then join him in the United Kingdom. From October to December, Medley will work at the UKHO Product Management Department, where she will learn the UKHO’s best practices for management of their products. (Watch this space for Medley’s posts about her experiences in the UK!)

Posted August 13, 2015 by NOAA Office of Coast Survey in Nautical charts

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

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

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.

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