Linda Kurtz: Hydrographic Surveys – Not your Mama’s Maps! August 17, 2019

NOAA Teacher at Sea

Linda Kurtz

Aboard NOAA Ship Fairweather

August 12-23, 2019


Mission: Cascadia Mapping Project

Geographic Area of Cruise: Northwest Pacific

Date: 8/17/2019

Weather Data from the Bridge

August 17th 2019

Latitude & Longitude: 43◦ 53.055’ N 124◦ 47.003’W
Windspeed: 13 knots
Geographic Area: @10-15 miles off of the Oregon/California coast
Cruise Speed:  12 knots
Sea Temperature 20◦Celsius
Air Temperature 68◦Fahrenheit

Future hydrographer button
Is this you?

Navigation is how Fairweather knows its position and how the crew plans and follows a safe route.  (Remember navigation from the last post?)  But what “drives” where the ship goes is Hydrographic survey mission.  There is a stunning amount of sea floor that remains unmapped, as well as seafloor that has not been mapped following a major geological event like an earthquake of underwater volcano.

Why is Hydrography important?  As we talked about in the previous post, the data is used for nautical safety, creating detailed maps of the ocean floor,  setting aside areas are likely abundant undersea wildlife as conservation areas, looking at the sea floor to determine if areas are good for wind turbine placement, and most importantly to the residents off the Pacific coast, locating fault lines — especially subduction zones which can generate the largest earthquakes and cause dangerous tsunamis.

In addition to generating the data needed to update nautical charts, hydrographic surveys support a variety of activities such as port and harbor maintenance (dredging), coastal engineering (beach erosion and replenishment studies), coastal zone management, and offshore resource development. Detailed depth information and seafloor characterization is also useful in determining fisheries habitat and understanding marine geologic processes.

The history of hydrographic surveys dates back to the days of Thomas Jefferson, who ordered a survey of our young nation’s coast.   This began the practice and accompanying sciences of the coastal surveys.  The practice of surveys birthed the science of Hydrography (which we are actively conducting now) and the accompanying science of Bathymetry (which we will go into on the next post.)  This practice continues of providing nautical charts to the maritime community to ensure safe passage into American ports and safe marine travels along the 95,000 miles of U.S. Coastline. 

Want to learn more about Hydrographic Survey history?  Click on THIS LINK for the full history by the NOAA.

Scientists have tools or equipment that they use to successfully carry out their research.  Let’s take a look at a few of the tools hydrographic survey techs use:

Want to learn more about the science of SONAR? Watch the video below.

ps://www.youtube.com/watch?v=8ijaPa-9MDs

On board Fairweather (actually underneath it) is the survey tool call a TRANSDUCER which sends out the sonar pulses.

Multibeam sonar illustration
Multibeam sonar illustration

The transducer on Fairweather is an EM 710- multibeam echo sounder which you can learn more about HERE

The Transducer is located on the bottom of the ship and sends out 256 sonar beams at a time to the bottom of the ocean.  The frequency of the 256 beams is determined by the depth from roughly 50 pings per second to 1 ping every 10 seconds.  The active elements of the EM 710 transducers are based upon composite ceramics, a design which has several advantages, which include increased bandwidth and more precise measurements. The transducers are fully watertight units which should give many years of trouble-free operation.  This comes in handy since the device in on the bottom of Fairweather’s hull!

Here is the transducer on one of the launches:

transducer
View of transducer on a survey launch

The 256 sonar beams are sent out by the transducer simultaneously to the ocean floor, and the rate of return is how the depth of the ocean floor is determined.  The rate of pulses and width of the “swath” or sonar beam array is affected by the depth of the water.  The deeper the water, the larger the “swath” or array of sonar beams because they travel a greater distance.  The shallower the water, the “swath” or array of sonar beams becomes narrower due to lesser distance traveled by the sonar beams.

The minimum depth that this transducer can map the sea floor is less than 3 meters and the maximum depth is approximately 2000 meters (which is somewhat dependent upon array size).  Across track coverage (swath width) is up to 5.5 times water depth, to a maximum of more than 2000 meters. This echo sounder is capable of reaching deeper depths because of the lower frequency array of beams. 

The transmission beams from the EM 710 multibeam echo sonar are electronically stabilized for roll, pitch and yaw, while they receive beams are stabilized for movements. (The movement of the ship) What is roll, pitch, and yaw? See below – these are ways the Fairweather is constantly moving!

Roll, Pitch, and Yaw
Roll, Pitch, and Yaw

Since the sonar is sent through water, the variable of the water that the sonar beams are sent through must be taken into account in the data. 

Some of the variables of salt water include: conductivity (or salinity) temperature, depth, and density.

Hydrographic scientists must use tools to measure these factors in sea water, other tools are built into the hydrographic survey computer programs. 

One of the tools used by the hydrographic techs is the XBT or Expendable Bathy Thermograph that takes a measurement of temperature and depth.  The salinity of the area being tested is retrieved from the World Ocean Atlas which is data base of world oceanographic data. All of this data is transmitted back to a laptop for the hydrographers.  The XBT is an external device that is launched off of the ship to take immediate readings of the water. 

Launching the XBT:  There is a launcher which has electrodes on it, then you plug the XBT probe to the launcher and then XBT is launched into the ocean off of the back of the ship.  The electrodes transmit data through the probe via the 750-meter copper wire.  The information then passes through the copper wire, through the electrodes, along the black wire, straight to the computer where the data is collected.  This data is then loaded onto a USB then taken and loaded into the Hydrographic data processing software.  Then the data collected by the XBT is used to generate the sound speed profile, which is sent to the sonar to correct for the sound speed changes through the water column that the sonar pulses are sent through.  The water column is all of the water between the surface and seafloor. Hydrographers must understand how the sound moves through the water columns which may have different densities that will bend the sound waves.  By taking the casts, you are getting a cross section “view” of the water column on how sound waves will behave at different densities, the REFRACTION (or bending of the sound waves) effects the data.

See how the XBT is launched and data is collected below!

Videos coming soon!

The other tool is the MVP or moving vessel profiler which takes measurements of conductivity, temperature, and depth.  These are all calculated to determine the density of the water.  This is a constant fixture on the aft deck (the back of the ship) and is towed behind the Fairweather and constantly transmits data to determine the speed of sound through water.  (Since sonar waves are sound waves.)

MVP and launching wench
MVP (left) and the launching wench (right)

The sonar software uses this data to adjust the calculation of the depth, correcting for the speed of sound through water due to the changes in the density of the ocean.  The final product?  A detailed 3d model of the seafloor!

current survey area
Our current survey area! (Thanks Charles for the image!)

All of this data is run through the survey software.  See screen shots below of all the screens the hydrographers utilize in the course of their work with explanations.  (Thanks Sam!)  It’s a lot of information to take in, but hydrographic survey techs get it done 24 hours a day while we are at sea.  Amazing!  See below:

ACQ software screenshot
Hydrographic Survey “Mission Control”
HYPACK Acquisition Software
HYPACK Acquisition Software
Real time coverage map
Real time coverage map

Did You Know?  An interesting fact about sonar:  When the depth is deeper, a lower frequency of sonar is utilized.  In shallower depths, a higher sonar frequency. (Up to 900 meters, then this rule changes.)

Question of the Day:  Interested in becoming a hydrographic survey tech?  See the job description HERE.

Challenge yourself — see if you can learn and apply the new terms and phrases below and add new terms from this blog or from your research to the list!

New Terms/Phrases:

Multibeam sonar

Sound speed

Conductivity

Salinity

Sonar

Sound waves

Refraction

Water column

Roll, Pitch, and Yaw

Animals seen today:

Humpback Whale

Bathymetry and USGS friends coming soon!

Plot room
Hydro-technician Sam Candio (right) collaborating with USGS Research Geologist James Conrad and Physical Scientist Peter Dartnell.

Meg Stewart: What Does the Seafloor Look Like? Hydrography Can Tell Us, July 11, 2019

NOAA Teacher at Sea

Meg Stewart

Aboard NOAA Ship Fairweather

July 8 – 19, 2019


Mission: Cape Newenham Hydrographic Survey

Geographic Area of Cruise: Bering Sea and Bristol Bay, Alaska

Date: July 11, 2019

Weather Data from the Bridge
Latitude: 58° 36.7 N
Longitude: 162° 02.5 W
Wind: 1 knot N
Barometer: 1011.0 mb
Visibility: 10 nautical miles
Temperature: 58° F or 14° C
Weather: Partly cloudy, no precipitation

Red Sky
“Red sky at night, sailors’ delight. Red sky in morning, sailors take warning.” This old mariner’s adage did NOT prove to be true when I saw this sunrise viewed from NOAA Ship Fairweather at 5:21am yesterday. It turned out to be a perfect delight for a surveying day!


What is NOAA and the Teacher at Sea program?

You may be wondering what, exactly, am I doing going “to sea” with NOAA. First off, NOAA stands for the National Oceanic and Atmospheric Administration and originates back to 1807 with Thomas Jefferson founding the U.S. Coast and Geodetic Survey (as the Survey of the Coast) with a mission to provide nautical charts to the maritime community for safe passage into American ports. Over time, the Weather Bureau was added and then the U.S. Commission of Fish and Fisheries was developed. In 1970, these three agencies were combined under one umbrella organization and named NOAA, an agency that supports accuracy and precision of physical and atmospheric sciences, protection of life and property, and stewardship of natural resources. NOAA is within the Department of Commerce.

Meg on flying bridge
I am standing on the flying bridge of the Fairweather where you get a fantastic 360° view.

NOAA’s Teacher at Sea (TAS) program has existed since 1990, sending over 800 teachers on NOAA research cruises. The TAS mission is “to give teachers a clearer insight into our ocean planet, a greater understanding of maritime work and studies, and to increase their level of environmental literacy by fostering an interdisciplinary research experience.”  There is usually just one teacher sent per leg of a mission, that way the TAS gets full exposure to the research process and attention from the crew, scientists and staff on the ship. And it is true, everyone onboard has been friendly, helpful, welcoming, and willing to answer any question I might have, like, where is C deck? (That’s where my stateroom is located).


Science and Technology Log

Now that you understand NOAA’s mission, it should not surprise you that I am on a research cruise that is mapping a part of the seafloor that has not had detailed soundings. “Soundings” means the action or process of measuring the depth of the sea or other body of water. See the map below as that is where I am right now, in Bristol Bay. By the way, NOAA nautical charts are available for free at this NOAA site.

Bristol Bay nautical chart
The NOAA nautical chart of Bristol Bay, Cape Newenham and Hagemeister Strait. Note that where there are small numbers in the white and blue sections of the chart (that is all water), you can see the sounding depths to surface shown in fathoms. The red polygon is drawn on by me. We are working in the upper, northwest part of that “poorly mapped” section. Notice that there are essentially no soundings in that region.

When I’ve told friends, family and students that I was chosen to be on a NOAA research vessel that was compiling a detailed map of the sea floor off of Alaska, it was met with great surprise. “The ocean floor hasn’t been mapped before? How could that be?” In fact, more than 80 percent of the ocean bottom has not been mapped using modern, highly precise technologies.  But we do have a very coarse ocean floor – or bathymetric – map, created in the early 1950s by Marie Tharp using sounding data collected by the U.S. military and her collaborator Bruce Heezen. Tharp’s early map of the sea floor beautifully revealed the Mid-Atlantic Ridge and added another piece of evidence in support of the theories of continental drift plate tectonics. There’s a terrific Cosmos: A Spacetime Odyssey episode featuring Tharp.

1977 colorized ocean floor map
This is the Tharp and Heezen (1977) colorized ocean floor map. This map is used under the Creative Commons license.

Why we need a more detailed bathymetry map than the one created by Tharp and Heezen can be explained by the original mission of the early version of NOAA. Jefferson wanted to build a “…survey to be taken of the coasts of the United States…” in order to provide safe passage of ships to ports within the navigable waters of the U.S. As the Bristol Bay chart above shows, there are still coastal areas that have limited to no data. Without detailed charts, mariners cannot know where the shallower waters are (called shoals), or rock obstructions, shifted underwater sand bars, shipwrecks, or other hindrances that cause safety concerns to the movement of boats.

The hydrographic Survey Team on the NOAA Ship Fairweather use several 30 foot boats, called launches, with a multibeam echosounder attached to the hull (the bottom of the ship). The multibeam echosounder uses sonar and is a device useful for both shallow and deep water. In a nutshell, depth measurements are collected by calculating the time it takes for each of the sound pulses to travel from the echosounder through the sea water to the ocean floor and back again. The distance from the instrument to the seafloor is calculated by multiplying the travel time by the speed of sound through seawater, which is about 1,500 meters/second or 4,921 feet/second. Right before a hydrographic survey is started, the team collects information on the conductivity, temperature and depth of the sea water, as temperature and salinity will modify the density and change the travel time of the sonar pulses. The video below can explain the process further.

This NOAA video explains multibeam sounding and hydrographic operations.
launch with echosounder
A launch on a lift right before going out to survey. The multibeam echosounder is permanently fixed to the bottom of the hull. It’s a square, rigid box that sits flat against the hull in front of the keel.
Ali in a launch
This is Ali Johnson in the cabin of a launch. She is a hydrographic survey technician and is analyzing the multibeam echosounder data as it is being collected. The length of a launch is 32 feet, and all the technology needed for the hydrographic surveys are directly on boats in the cabin. Post-processing, or stitching the completed surveys into one comprehensive product, is done “back in the office” on Ship Fairweather.

The software used to collect the soundings is created by the multibeam echosounder manufacturer, so the collection of millions of points on a transect is seamless. Data collection runs are taken over multiple days and several “legs” or extended periods of time when the crew are all out at the same time on the Fairweather.  Following collection transects, the data are then post-processed using Caris HIPS and SIPS, which is the software that the Fairweather hydrographers use for data processing.

screen showing bathymetry
A close-up of one of the monitors that shows what the sounding data look like. By looking at these data returns, the hydrographers can tell immediately if something is not right with the equipment. The two windows that show maps colored red to yellow to blue (top right and bottom left) show the bathymetry. The red areas are shallow depths and the blue are deeper depths, relatively speaking. Also notice the window at the bottom right with a triangle and circle within the triangle; that is showing the fan-shape of the echosoundings.


Personal Log

We’ve motored to a new location, Cape Newenham, which is the name of this mission, so we will be here for about a week. When we got underway, the ship got to really rocking and my stomach could not handle it. I had one bad night but I am now fine and ship shape!

Cape Newenham is at latitude 58°N so we are up close to the Arctic Circle (66.5°N). At this time of year, there are about 5 hours of darkness per night here in Alaska, which is really cool. Compare that what we have in New York…

Anchorage v NYC
For July 11, 2019, the number of daylight hours in Anchorage, AK (closest large city to where I am now) is 18 hours and 41 minutes. Times of sunrise and sunset are also given….the sun sets at 11:25pm today! And in NYC, NY (where my school is located), you are getting four fewer daylight hours, or about 15 hours of light. Again, times of sunrise and sunset are shown. Source for both: https://www.timeanddate.com/sun/usa
Launches and Fairweather
Launches waiting to get underway. All boats going out for surveys stay close to the Fairweather until everyone is securely in their boat, just in case of MOB (man overboard).
Fairweather anchored
This is where Ship Fairweather is anchored for the next few days, as the survey crews transect the project area. We are on the southern side of Cape Newenham. Again, the terrain is tree-less, though we are now adjacent the mainland of Alaska. I’ve seen so many types of sea birds, but the puffins are the best because they seem to not have figured out how to fly. I hear there are walrus in the area, but I haven’t spotted one as yet.


Did You Know?

You probably know that Charles Darwin was the naturalist on board the HMS Beagle which set sail on December 27,1831. Over the nearly five years the Beagle was at sea, Darwin developed his ideas on natural selection and evolution of species. But what you might not know is that the captain of the Beagle, Robert FitzRoy, was an officer in the Royal Navy, a meteorologist and hydrographer. In fact, the primary mission of the Beagle was to survey the coastline of South America and, in particular, the Strait of Magellan, at the southernmost tip. Better, more accurate charts were needed by the British government, to navigate the treacherous, rough waters of the channels. In addition, FitzRoy was a protégé of Francis Beaufort (who developed the Wind Force Scale which is still used to help explain wind speed) and both worked together to create the science of weather forecasting.


Quote of the Day

“In every outthrust headland, in every curving beach, in every grain of sand there is the story of the earth.” – Rachel Carson

Jill Bartolotta: Sounds of the Deep, June 5, 2019

NOAA Teacher at Sea

Jill Bartolotta

Aboard NOAA Ship Okeanos Explorer

May 30 – June 14, 2019

Mission:  Mapping/Exploring the U.S. Southeastern Continental Margin and Blake Plateau

Geographic Area of Cruise: U.S. Southeastern Continental Margin, Blake Plateau

Date: June 5, 2019

Weather Data:

Latitude: 29°01.5’ N

Longitude: 079°16.0’ W

Wave Height: 2 feet

Wind Speed: 10 knots

Wind Direction: 128

Visibility: 10 nm

Air Temperature: 27.7°C

Barometric Pressure: 1021.3

Sky: few

Science and Technology Log

What is sonar?

Sonar is the use of sound to describe the marine environment. Sonar can be compared to satellites that use light to provide information about Earth, but instead of light, sound is used. It is used to develop nautical charts, detect hazards under the water, find shipwrecks, learn about characteristics of the water column such as biomass, and map the ocean floor. There are two types of sonar, active and passive. Active sonar is sonar that sends out its own sound wave. The sonar sends a sound wave (ping) out into the water and then waits for the sound to return. The return sound signal is called an echo. By assessing the time, angle, and strength of the return sound wave or echo one can learn many details about the marine environment. Passive sonar does not actively send out a sound ping, but rather listens for the sound from other objects or organisms in the water. These objects may be other vessels and these organisms may be whales or marine ecosystems such as coral reefs.

Sound waves move through the water at different speeds. These speeds are known as frequencies and the unit of measurement for sound is a hertz (Hz). Lower frequencies (example 18 kHz) are able to go farther down because they move slower and have more power behind them. It is like when a car goes down your street, pumping the bass (always seems to happen when I am trying to sleep) and you can hear it for a long time. That is because it is a low frequency and has longer wave lengths. Higher frequencies (example 200 kHz) move faster, but have less power. The sound waves should reach the bottom, an object, or biomass in the water column, but there may be no return or echo. High frequency sound waves are closer together. High frequencies give you a good image of what is happening near the surface of the water column and low frequencies give you a good idea of what is happening near, on, or under the ocean floor.

Type of Sonar on Okeanos Explorer

There are many types of sonar and other equipment aboard Okeanos Explorer for use during mapping operations. All have different capabilities and purposes. Together they provide a complete sound image of what is happening below us.

Kongsberg EM302 Multibeam Sonar

Multibeam sonar sends sound out into the water in a fan pattern below the hull (bottom) of the ship. It is able to map broad areas of the water column and seafloor from depths of 10 meters to 7,000 meters. Only the deepest trenches are out of its reach. It is the most appropriate sonar system to map seafloor features such as canyons and seamounts. The fan like beam it emits is 3-5.5x the water depth with a max swath range of 8 km. However, when you get to its depths below 5,000 meters the quality of the sound return is poor so scientists keep the swath range narrower to provide a higher quality of data return. The widest swath area scientists can use while maintaining quality is a depth of 3,300-5,000 meters. The user interface uses a color gradient to show you seafloor features (red=shallow and purple=deep).

Swath ranges for the multibeam sona
Swath ranges for the multibeam sonar at various depths. The y-axis shows the water depth in meters and the x-axis shows the swath width in meters. Photo credit: SST Charlie Wilkins, NOAA Ship Okeanos Explorer
Multibeam Sonar information
Some of the information that is collected using the multibeam sonar with labels describing their purpose. Photo Credit: NOAA OER

Backscatter

Backscatter uses the same pings from the multibeam. People use backscatter to model or predict physical or biological properties and composition of the sea floor. The coloring typically is in grayscale. A stronger echo looks brighter in the image. A weaker echo looks darker in the image. It gives you a birds-eye view of seafloor characteristics such as substrate density and seafloor features.

Backscatter and Bathymetry
Top image is backscatter showing you a birds-eye view of the ocean floor. The bottom image shows you what it looks like when backscatter is overlaid over the bathymetry layer. You are able to see intensity of the sound return, but floor features are more noticeable. Photo credit: NOAA OER

XBT

An Expendable Bathy-Thermograph (XBT) provides you with information on the temperature gradients within the water. When the temperature profile is applied to a salinity profile (taken from World Ocean Atlas) you are able to determine sound velocity or the rate at which the sound waves can travel through the water. When sound moves through water it does not move in a straight line. Its path is affected by density which is determined by water type (freshwater or saltwater) and temperature. Freshwater is less dense than saltwater and cold water is denser than warm water. The XBT information accounts for sound refraction (bending) through various water densities. When near shore XBTs are launched more frequently because the freshwater inputs from land alter density of the water and temperatures in the water column are more varied. XBTs are launched less frequently when farther from shore since freshwater inputs are reduced or nonexistent and the water column temperature is more stable. However, ocean currents such as the Gulf Stream (affecting us on this cruise) can affect density as well. The Gulf Stream brings warm water from the Gulf of Mexico around the tip of Florida and along the eastern coast of the United States. Therefore, one must also take into account which ocean currents are present in the region when determining the launch schedule of XBTs.

Loading the XBT Launcher
Senior Survey Technician Charlie Wilkins and Explorer in Training, Jahnelle Howe, loading the XBT launcher. XBTs are launched off the stern of the ship.
XBT Capture
Sound speed or velocity is determined by the density of the water, which is determined by temperature and salinity. Focus on the blue line in each graph. The first graph takes the information from the temperature and salinity graphs to determine sound speed. If we look at the first graph, we see that sound speed slows with depth. Sound speed slows because according to the second graph the temperature is colder making the water denser, thus affecting sound speed. Salinity does not vary much according to the third graph so its effect on density is most likely limited. Photo credit: NOAA OER

Simrad EK60 and EK80 Split-beam Sonar

Split-beam sonar sends out sound in single beam of sound (not a fan like the multibeam). Each transducer sends out its own frequency (example 18 kHz, 38 kHz, 70 KHz, 120 kHz, and 200 kHz). Some frequencies are run at the same time during mapping operations. Mapping operations typically do not use the 38 kHz frequency since it interferes with the multibeam sonar. Data collected with the use of the EK60 or EK80 provides information about the water column such as gaseous seeps, schools of fish, and other types of dense organism communities such as zooplankton. If you remember my “did you know” from the second blog, I discussed how sonar can be used to show the vertical diurnal migration of organisms. Well the EK60 or EK80 is the equipment that allows us to see these biological water column communities and their movements.

Water column information
Water column information collected with the EK60 or EK80 split beam sonar. If you look at the first row you can see, in the image to the left, the blue dots are at the top and in the second image the blue dots are moving back down into the water column as the sun rises. The process of organisms’ movement in the water column at night to feed is known as vertical diurnal migration. Photo Credit: NOAA OER

Knudsen 3260 Sub-bottom Profiler

The purpose of using a sub-bottom profiler is to learn more about the layers (up to 80 meters) below the ocean floor. It works in conjunction with the sonar mapping the ocean floor to provide more information about the bottom substrate, such as sediment type and topography features. Sub-bottom data is used by geologists to better understand the top layers of the ocean floor. A very low frequency is used (3.5 kHz) because it needs to penetrate the ocean sediment. It will give you a cross section of the sea floor so floor features can be detected.

Cross section of the ocean seafloor
Cross section of the ocean seafloor shows you substrate characteristics. Photo Credit: NOAA OER

Telepresence

Telepresence aboard the ship allows the science team to get mapping products and raw data to land on a daily basis. The science team can also live feed data collection to shore in real time. By allowing a land based shore team to see the data in real time you are adding another system of checks and balances. It is one more set of eyes to make sure the data being collected looks correct and there are no issues. It also allows a more collaborative approach to mapping, since you are able to involve a worldwide audience in the mission. Public viewers can tune in as well.  Support for the technology needed to allow telepresence capabilities comes in partnership with the Global Foundation of Ocean Exploration (GFOE). With GFOE’s help, the protocols, high-speed satellite networks, Internet services, web and social media interfaces, and many other tools are accessible when out to sea. The NOAA Office of Exploration and Research (OER) provides the experts needed to develop, maintain, and operate the telepresence systems while at sea, but also at shore through the Exploration Command Centers (ECCs) and the University of Rhode Island’s Inner Space Center.

Live interaction
Live interaction with Okeanos Explorer, Inner Space Center at URI/GSO, and a group of high school students. Photo credit: NOAA OER

All in all, the equipment aboard Okeanos Explorer is impressive in its abilities to provide the science team with a high quality and accurate depiction of the ocean floor and water column. The science team aboard is able to interpret the data, clean out unwanted data points, store massive data files on computers, and send it back to land daily, all while rocking away at sea. Very impressive and very cool!

Personal Log

I learned all about memes today. Apparently they are very popular on the ship. So popular, we are even in the middle of a meme contest. For those of you unfamiliar to memes like I was, a meme is a funny picture with a clever caption that makes you laugh or relates to something in your life. After my tutorial in meme making, we had a great time out on the bow of the ship playing corn hole and hanging out. The night was beautiful. The humidity subsided and there was a great breeze. After the sun set, I watched the stars come out and then went inside to learn more about the mapping process. I am starting to get a better understanding of what the science team is doing. You know the how and the why of it all. After I couldn’t keep my eyes open any longer, I made my nightly venture out onto the bow to look from some bioluminescence, the glittering of zooplankton in the night. A magical site. I will leave you wondering how the ocean glitters until one of my future blogs when I describe the process of bioluminescence.

Corn hole
General Vessel Assistant Sidney Dunn (left) and General Vessel Assistant Christian Lebron (right) playing corn hole on the bow at sunset.

Did You Know?

The SOFAR (Sound Fixing and Ranging) channel occurs in the world’s oceans between depths of 800 to 1000 meters in the water column. Because of the density and pressure around this channel, sound waves travel for an extended distance. It is thought that fin whales travel to this channel to communicate with other fin whales many kilometers away.

Lona Hall: Launchin’ and Lunchin’ Near Kodiak Island, June 6, 2019

NOAA Teacher at Sea

Lona Hall

Aboard NOAA Ship Rainier

June 3 – 14, 2019


Mission: Kodiak Island Hydrographic Survey

Geographic Area of Cruise: Kodiak Island, Alaska

Date: June 6, 2019

Time:  2000 hours

Location: Underway to Isthmus Bay, Kodiak Island

Weather from the Bridge:

Latitude: 57°39.2266’ N
Longitude: 152°07.5163’ W
Wind Speed: 11.6 knots
Wind Direction: NW (300 degrees)
Air Temperature: 11.37° Celsius
Water Temperature: 8.3° Celsius


Science and Technology Log

Lona on launch RA-5
Yours truly, happy on RA-5

Today I went out on a launch for the first time.  The plan was to survey an area offshore and then move nearshore at low tide, with the water at its lowest level on the beach of Kodiak Island.  Survey Techs, Carl Stedman and Christina Brooks, showed me the software applications used to communicate with the coxswain and collect data. To choose the best frequency for our multibeam pulse, we needed to know the approximate depth of the area being surveyed.  If the water is deeper, you must use lower frequency sound waves, since higher frequency waves tend to attenuate, or weaken, as they travel. We chose a frequency of 300 kilohertz for a 60 meter depth. Periodically, the survey techs must cast a probe into the water.  The Sea-bird SeaCAT CTD (Conductivity, Temperature, Depth) measures the characteristics of the water, creating a sound velocity profile. This profile can tell us how quickly we should expect sound waves to travel through the water based upon the water’s temperature, salinity, and pressure.

Seabird SeaCAT CTD
Seabird SeaCAT CTD
Carl Stedman deploying the probe
Carl Stedman deploying the probe

Using the sound velocity profile allows the computer’s Seafloor Information System (SIS) to correct for changes in water density as data is being collected.  Once the profile was transmitted to SIS, we were ready to begin logging data.

Imagine that you are mowing your lawn.  To maximize efficiency you most likely will choose to mow back and forth in relatively straight paths, overlapping each new row with the previous row.  This is similar to how the offshore survey is carried out. As the boat travels at a speed of about 7 knots, the Kongsberg EM2040 multibeam sonar transducer sends out and receives pulses, which together create a swath.  The more shallow the water, the wider the base of the swath.

Close up of chart
Close up of chart, showing depth gradient by color

After lunch we changed to a nearshore area closer to Kodiak Island between Sequel Point and Cape Greville. It was important to wait for low tide before approaching the shore to avoid being stuck inshore as the tide is going out.  Even so, our coxswain was very careful to follow the edges of the last swaths logged. Since the swath area extends beyond the port and starboard sides of the boat, we could collect data from previously uncharted areas without driving directly above them.  In this way we found many rocks, invisible to the naked eye, that could have seriously damaged an unlucky fisherman!


Career Focus – Able Seaman

Our coxswain driving the boat today was Allan Quintana.  

Allan, aka "Q", driving the boat
Allan, aka “Q”, driving the boat

As an Able Seaman, Allan is part of the Deck Department, which functions primarily to keep track of the ship, manage the lines and anchoring, and deploy and drive the launches.  Allan started out working for the Navy and later transitioned to NOAA. A Miami native, he told me how he loves working at sea, in spite of the long stretches of time away from his friends and family back home.


Personal Log

If you have never been on a boat before, it is a unique experience. Attempts have been made by poets, explorers, scientists, naturalists, and others throughout history to capture the feeling of being at sea.  Although I’ve read many of their descriptions and tried to imagine myself in their shoes, nothing compares to experiencing it first-hand.

Standing on the bow of the anchored ship, looking out at the water, my body leaning to and fro, rising and falling, I am a sentient fishing bobber, continuously rocking but not really going anywhere.  My head feels somehow both heavy and light, and if I stand there long enough, I just might fall asleep under the spell of kinetic hypnosis. The motion of the launch is different. A smaller boat with far less mass is bullied by the swells. For a new crew member like me, it’s easy to be caught off guard and knocked over, unless you have a good grip. I stand alert, feet apart, one hand clasping a rail, as the more experienced crew move about, casually completing various tasks. I wonder how long it would take to become accustomed to the boat’s rising and falling.  Would my body gradually learn to anticipate the back and forth rocking? Would I eventually not feel any movement at all?

View over the bow
A ship with a view


Word of the Day

draft – the vertical distance between the waterline and the hull of a boat, a.k.a. the draught

The draft of NOAA Ship Rainier is 17 feet.

Meredith Salmon: Deciphering the Data! July 30, 2018

NOAA Teacher at Sea

Meredith Salmon

Aboard NOAA Ship Okeanos Explorer

July 12 – 31, 2018

Mission: Mapping Deep-Water Areas Southeast of Bermuda in Support of the Galway Statement on Atlantic Ocean Cooperation

Date: July 30, 2018

Latitude: 35.27°N

Longitude: 73.24.°W

Air Temperature: 27.5°C

Wind Speed:  18.17 knots

Conditions: Partly Sunny  

Depth: 3742.65 meters

Qimera is a hydrographic processing software that was used during this expedition. This computer program allows scientists to edit and process the survey line data as it was being collected. 

Qimera Survey Area

The survey area 200 nautical miles off the coast of Bermuda projected in Qimera. Warmer colors indicate depths close to 4,000 meters while the cooler colors represent deeper regions up to 5,500 meters.

To successfully edit incoming multibeam data, it was necessary to isolate a specific section of the line and use Qimera’s 3D Editing Tool. The 3D Editing Tool was utilized to remove outliers that skew the data.

Essentially, each colorful point in the diagram below is a sounding from the multibeam sonar. The soundings are return signals that bounce back and reach the receivers on the sonar. When scientists are previewing and editing data, certain points are considered outliers and are rejected. The rejected points are shown as red diamonds in the diagram below. Once the edits are made, they are saved, and the surface is updated.  

3D editor qimera

Examples of a data set being processed by the 3D Editing Tool in Qimera. The red dots are rejected points that will not be included when the data is completely processed.

It is especially important to ensure that we are collecting as much data as possible as we continue to survey this area. In order to accomplish this, factors such as required resolution, sea state, water depth and bottom type are used to determine line plans.  By partially overlapping lines, we ensure there is quality data coverage on the outside beams. More overlap tends to mean denser, high quality coverage which will allow our team to develop accurate maps of the seafloor.

Qimera Survey Area

Side view of a section of the survey area projected in Qimera. The warmer colors indicate depths around 4,000 meters while the cool colors indicate depths closer to 5,500 meters.

Another program that was used to process data was known as Fledermaus. This interactive 4D geospatial processing and analysis tool is used to reproject Qimera projects as well as export the Daily Product that was completed and sent onshore where it is publicly available. We also projected the edited data on Google Earth (see below) and would include this in the Daily Product that was sent to shore as well.

Google Earth view

The survey and transit lines are displayed in blue, while previously mapped areas of the seafloor are shown in green.

 

Personal Log

Now that we have left the survey area, we are transiting back to Norfolk and still collecting and processing data. We are scheduled to arrive early on the 31st and a majority of us will depart that evening. Since we are still collecting return transit data, it is still necessary for processing to occur. Although we’ve been working diligently, we still like to make time for fun. On Friday night, we hosted a Finer Things Club Gathering complete with fancy cheese, crackers, sparkling apple juice, and chocolate! It was great! On Saturday, we played the final cribbage tournament game as well as other board games, and on Sunday we had an ice cream party!

Finer Things Club

The Mapping Team hosts a Finer Things Club Meeting complete with sparkling apple juice, crackers, cheese, and chocolate!

Finer Things

Our fancy spread of gourmet snacks!

final match

Charlie and Mike in the FINALS!

ice cream social

Sundaes on Sunday!

 

View of calm seas

Super calm seas on the way home!

Calm Seas

Calm Seas

 

Did You Know?

One of the first breakthroughs in seafloor mapping using underwater sound projectors was used in World War I.

Resources:

https://oceanexplorer.noaa.gov/explorations/03fire/background/mapping/mapping.html

David Tourtellot: A Musical Perspective of Sonar, July 24, 2018

NOAA Teacher at Sea

David Tourtellot

Aboard NOAA Ship Thomas Jefferson

July 9-26, 2018

Mission:  Hydrographic Survey – Approaches to Houston

Geographic Area of Cruise: Gulf of Mexico

Date: July 24th, 2018

Weather Data from the Bridge

Latitude: 29°09.1270’N

Longitude: 093°46.5544’W

Visibility: 5 Nautical Miles

Sky Condition: 8/8

Wind: Direction: 70.1°, Speed: 13.3 knots

Temperature:

Seawater: 29.24°C

Air: Dry bulb:26.9°C          Wet bulb: 24.7°C

 

Science and Technology Log

Coming to NOAA Ship Thomas Jefferson, I was eager to learn all I could about sonar. I am amazed that we have the ability to explore the ocean floor using sound.

uncharted wreck

An uncharted wreck discovered by NOAA Ship Thomas Jefferson

Over the course of my previous blog entries, I have described the tools and processes used to survey using sonar. This time, I am going to try to frame the sounds that the sonars are using in a musical context, in the hope that doing so will help students (and myself) better understand the underlying concepts.

Note – many aspects of music are not standardized. For the purpose of this blog post, all musical tuning will be in equal temperament, at A=440. When I reference the range of a piano, I will be referencing a standard 88-key instrument. Many of the sonar frequencies do not correspond exactly to an in-tune pitch, so they have been written to the nearest pitch, with a comment regarding if the true frequency is higher or lower than the one written.

In sonar and in music, when considering soundwaves it is important to know their frequency, a measure of how many waves occur over the course of a set period of time. Frequency is measured in a unit called Hertz (abbreviated as Hz), which measures how many soundwaves occur in one second. One Hertz is equal to one soundwave per second. For example, if you heard a sound with a frequency of 100Hz, your ears would be detecting 100 soundwaves every second. Musicians also are concerned with frequency, but will use another name for it: pitch. These words are synonymous – sounds that are higher in pitch are higher in frequency, and sounds that are lower in pitch are lower in frequency.

Below are the eight octaves of the note A that are found on a piano, each labeled with their frequency. The notes’ frequencies have an exponential relationship – as you move from low to high by octave, each note has a frequency that is double that of its predecessor.

Piano As with frequencies

The frequency of each A on a piano

The highest note on a piano, C, has a frequency of 4186.01Hz

Highest Note on a piano

The frequency of the highest note on a piano

Average, healthy young humans hear sounds ranging from 20Hz to 20,000Hz. All sounds outside of that range are inaudible to people, but otherwise no different from sounds that fall within the human range of hearing. The highest note we would be able to hear would be an E♭, at a frequency of 19,912.16Hz (a frequency of exactly 20,000Hz would fall in between E♭ and E♮, though would be closer to E♭). If put on a musical staff, it would look like this:

High Eb 19kHz

The frequency of the highest note in the human range of hearing

The hull of NOAA Ship Thomas Jefferson is equipped with several sonar transmitters and receivers, which can operate at a wide variety of frequencies.

TJ Sonar

The hull of NOAA Ship Thomas Jefferson, with several sonars. Note that the projectors that transmit lower frequencies are larger than the ones that transmit higher frequencies. This is similar to musical instruments – instruments that make lower sounds, like the tuba or the double bass, are larger than instruments that make higher sounds, like the trumpet or the violin

Higher frequencies provide higher resolution returns for the sonar, but they dissipate more quickly as they travel through water than lower frequencies do. Surveyors assess the depth of the water they are surveying, and choose the frequency that will give them the best return based on their conditions. Most of the sonar frequencies are too high for humans to hear. The ship’s multi-beam echo sounder has a variable frequency range of 200,000Hz-400,000Hz, though as I’ve been on board they’ve been scanning with it at 300,000Hz. Likewise, the multi-beam sonars on the launches have also been running at 300,000Hz. The ship has a sub-bottom profiler, which is a sonar used for surveying beneath the seafloor. It operates at a frequency of 12,000Hz, and has the distinction of being the only sonar on the ship that is audible to humans, however, we have not had a need to use it during my time aboard the Thomas Jefferson.

The ship’s side scan towfish (which I described in my previous blog entry) operates at 455,000Hz.

Here, we can see what those frequencies would look like if they were to be put on a musical staff.

Assorted Sonars and reference pitches

The frequencies of sonar, with reference pitches

Altering the frequency isn’t the only way to affect the quality of the reading which the sonar is getting. Surveyors can also change the pulse of the sonar. The pulse is the duration of the ping. To think about it in musical terms, changing the pulse would be akin to switching from playing quarter notes to playing half notes, while keeping the tempo and pitch the same. Different sonar pulses yield different readings. Shorter pulses provide higher resolution, but like higher frequency pings, dissipate faster in water, whereas longer pulses provide lower resolution, but can reach greater depths.

Personal Log

Mariners have a reputation for being a rather superstitious bunch, so I decided to ask around to see if that held true for the crew of the Thomas Jefferson. Overall, I found that most didn’t strictly adhere to any, but they were happy to share some of their favorites.

Everyone I spoke to told me that it is considered bad luck to leave port on a Friday, though the Commanding Officer, CDR Chris van Westendorp, assured me that you could counteract that bad luck by making three 360° turns to the left as soon as the ship is able. Many on the crew are also avid fishermen, and told me that bringing bananas aboard would lead to a bad catch, and one went so far as to be mistrustful of yellow lighters as well.

Certain tattoos are said to bring good luck – I was told that sailors often have a chicken and a pig tattooed on their feet. According to custom, those animals were often stored in wooden crates that would float if a ship went down, and having them tattooed onto you would afford you the same benefit. When asked if he was superstitious one of our helmsmen Jim proudly showed me a tattoo he has of a dolphin. He explained that having a sea creature tattooed on your body would prevent drowning. “It works!” he said with a grin, “I’ve never drowned!”

Several maritime superstitions deal with foul weather. Umbrellas are said to cause bad weather, as is split pea soup. Whistling while on the bridge is said to “whistle in the winds.” While not a superstition per se, many crew members told me variations of the same meteorological mantra: Red sky at night, sailor’s delight. Red sky in the morning, sailors take warning.

One of the NOAA Corps Officers aboard, ENS Garrison Grant, knew several old superstitions related to shipbuilding. When laying the keel (the first piece of the ship to be put into place), shipbuilders would scatter evergreen boughs and tie red ribbons around it to ward off witches. Historically, having women aboard was considered bad luck, though, conversely it was said that if they showed their bare breasts to a storm, it would subside. This is why several ancient ships had topless women carved into the masthead. Legend has it that in order to assure that a ship would float, when it was ready to be launched for the first time, virgins would be tied to the rails that guided the ship from the ship yard into the water. The weight of the ship would crush them, and their blood would act as a lubricant, allowing the ship to slide into the water for the first time. Yikes! Thankfully, as society became more civilized, this practice evolved into the custom of breaking a bottle of champagne against a ship’s bow!

Did you know? Musical instruments play an important role in ship safety! In accordance with maritime law, ships will use auditory cues to make other vessels aware of their presence in heavy fog. For large ships, this includes the ringing of a gong at regular intervals.

Latest Highlight: During this week’s fire drill, I got to try the fire hose. It was very powerful and a lot of fun!

David Tourtellot during a fire drill

David Tourtellot during a fire drill

Meredith Salmon: Setting Sail! July 12, 2018

NOAA Teacher at Sea

Meredith Salmon

Aboard NOAA Ship Okeanos Explorer

July 12 – 31, 2018

 

Mission: Mapping Deep-Water Areas Southeast of Bermuda in Support of the Galway Statement on Atlantic Ocean Cooperation

Geographic Area:  Atlantic Ocean, south of Bermuda

Date: July 12, 2018

Weather Data from the Okeanos Explorer Bridge – July 12, 2018

Latitude: 32.094°N

Longitude: 69.591°W

Air Temperature: 26.2°C

Wind Speed:  10.7 knots

Conditions: Sunny

Depth: 693 meters

Survey Area

Map showing the planned operations area for the expedition outlined in yellow. Image courtesy of the NOAA Office of Ocean Exploration and Research.

Science and Technology Log

According to the Oceanic Institute, the oceans cover 71% of the Earth’s surface. This is calculated to be 335,258,000 square kilometers! Recently, the Okeanos Explorer mapped over 1,000,000 square kilometers of the seafloor using high- resolution multibeam sonar. Although this may not seem like much, that region is larger than the areas of Arizona and Texas combined!

So why is it so important for the Okeanos Explorer to map the seafloor? The ocean’s terrain plays a very important role in ecosystems since underwater valleys determine currents and weather patterns, sea topography influences fishery management, and seamounts serve as protection against unpredictable storms. Therefore, high-resolution maps allow scientists to categorize marine habitats, provide information vital to protecting and tracking marine life, and enable us to make smart decisions for solid, sustainable conservation measures.

In order to successfully map the ocean floor, multibeam sonar is used. The Okeanos Explorer uses an EM 302 multibeam system that is designed to map a large portion of the ocean floor with exceptional resolution and accuracy. The EM 302 transducers point at different angles on both sides of the ship to create a swath of signals. Transducers are underwater speakers that are responsible for sending an acoustic pulse (known as a ping) into the water. If the seafloor or object is in the path of the ping, then sound bounces off the object and returns an echo to the transducer. The EM 302 has the ability to produce up to 864 depth soundings in a single ping. The time interval between the actual signal transmission and arrival of the return echo (two way travel time) are combined with a sound velocity profile to estimate depth over the area of the swath. In addition, the intensity of the return echo can be used to infer bottom characteristics that can be utilized for habitat mapping. Since the EM 302 creates high density, high-resolution data as well as water column features, this sonar system is ideal for exploring the seabed for geographic features.

The image below shows data being collected by the multibeam sonar on the Okeanos Explorer. The colors are used to indicate swath depth (warm colors indicate shallow waters while cool colors indicate deeper waters).

Multibeam sonar data

Multibeam sonar data including backscatter (lower left), depth (upper center) and water column data (lower center) from 7/12/2018 the Okeanos Explorer

 

As this data is being collected, it must be “cleaned” to eliminate any erroneous points.  Data is collected and cleaned in both the Dry Lab and Mission Control Room.

Dry Lab

Dry Lab, equipped with 12 computer monitors, used to process data onboard the Okeanos Explorer

Mission Control

Mission Control Room aboard the Okeanos Explorer

 

Since we have not reached the survey area yet, we have been monitoring the depth of our path thus far. We are collecting transit data which is considered to still be valuable data for unmapped seafloor area, but it may not be as high quality as focused mapping data. We will continue to collect transit data until we reach the survey area near Bermuda.

Personal Log

Life onboard the Okeanos Explorer has been a very interesting and fun learning experience! The ship runs on a 24/7 operation schedule and people are working diligently at all hours of the day. Everyone on the ship has been really welcoming and willing to share their stories and insights about their careers at sea. I am really looking forward to speaking with more people to learn about their experiences!

We set sail out of Norfolk today and began our 3.5 day/4 day transit to the survey area near Bermuda. This morning, we found out that we will need to schedule an emergency dry dock towards the end of our mission to solve an issue with a stern thruster necessary for ROV cruises. As a result, we will not be ending up in port in St. George, but we will still be able to map the area 200 nautical miles off the coast of Bermuda, so that is great!

norfolk out to sea!

NOAAS Okeanos Explorer (port quarter aspect) navigating the Elizabeth River outbound for sea from the NOAA pier in Norfolk, VA on July 12, 2018. [Photo by Commander Briana Hillstrom, NOAA

 

Did You Know?

Sonar is short for Sound Navigation and Ranging.

Check out this video for a visual representation of the process sonar uses to generate data! https://oceanservice.noaa.gov/caribbean-mapping/mapping-video.html

 

Resources:

https://www.oceanicinstitute.org/aboutoceans/aquafacts.html

https://oceanexplorer.noaa.gov/okeanos/one-million/welcome.html