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

Posted on July 26, 2018 by dtourtellot2018

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 24^th, 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.

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.

The frequency of each A on a piano

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

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:

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.

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.

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: Draggin’ The Line, July 21st, 2018

Posted on July 23, 2018 by dtourtellot2018

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 21^st, 2018

Weather Data from the Bridge

Latitude: 29° 11.6357’ N

Longitude: 093° 55.9746’W

Visibility: 10+ Nautical Miles

Sky Condition: 6/8

Wind: Direction: 224° Speed: 8.5 knots

Temperature:

Seawater: 30.4°C

Air: Dry bulb:31.5°C Wet bulb: 28.5°C

Science and Technology Log

In my previous post, I discussed the ship’s sonar. This time, I’ll go into more detail about the tools the Thomas Jefferson is using to complete its mission. The sonar that the ship uses is multi-beam echosounder sonar, which sends the pings down to the seafloor and receives echoes in a fan shape, allowing the ship to survey a wide swath beneath the ship.

An illustration of a ship using multi-beam sonar. Image courtesy of NOAA

In addition to the multi-beam sonar, NOAA Ship Thomas Jefferson utilizes two towfish, or devices that are towed in the water behind the ship.

The first is the side scan sonar. Like the multi-beam, this device uses pings of soundwaves to create images of its surroundings. However unlike the multi-beam, the side scan doesn’t capture any data from the area underneath it. Instead, it collects data to its sides. The side scan is connected to the ship via a cable, and is dragged through the water 6-15 meters above the seafloor. It is great for measuring the intensity of the return of the ping, which provides insights into the makeup of the seafloor.

The side scan towfish

The second towfish that the Thomas Jefferson is using is the MVP (like many things on the ship, MVP is an acronym, for Moving Vessel Profiler). The MVP truly gives the ship some of its most valuable data. As I discussed in my previous blog post, in order for us to accurately calculate the distance that the sonar’s pings are traveling, we need to know the amount of time it takes them to travel, as well as the velocity, or the speed, at which they’re moving. The singarounds I mentioned in my last post measure sound velocity, but only at the face of the sonar. Water conditions are not uniform – at the surface, water tends to be warmer, with less salinity. As you get deeper, however, the water tends to be colder and saltier. This means that the velocity of sound changes the deeper you get. Most of the time, the MVP rides just under the surface of the water, but periodically it will get cast down, to approximately 1 meter above the seafloor. It measures the water conditions of the entire water column from the surface to the seafloor, allowing us to calculate sound velocity all the way down.

The MVP towfish as it is being lowered into the water

The MVP measures the same water qualities as the CTD (a device I discussed in an earlier blog post), however, the MVP has a distinct advantage over the CTD. In order to use a CTD, the ship has to come to a stop while the CTD is lowered into the water. The MVP, however, can be used while the ship is in motion, which greatly increases productivity.

When surveying, many on the crew say it’s like mowing the lawn. The ship will capture a long stretch of data, called a line, and then turn around, and capture another stretch. 4% of these lines are cross lines, which run perpendicular, across a wide swath of lines of captured data. Cross lines allow the survey department to double check that the data they’ve captured is accurate.

A display of the lines of survey data the ship has captured. Cross lines can be seen running perpendicular to the majority.

Personal Log

The bridge of NOAA Ship Thomas Jefferson in the daylight

A couple of days ago, I went up to the bridge shortly after sunset, and I was surprised what I saw. All the lights were off, and the screens of the various instruments had been covered by red filters. I was told that this is for maintaining night vision when on watch. Red light interferes least with our night vision, so anything that gives off light is switched to red.

The bridge of NOAA Ship Thomas Jefferson at night

While on the bridge, I had the opportunity to ask ENS Garrison Grant (who had recently been selected for a promotion to Lieutenant Junior Grade – congratulations Garrison!) a little about the NOAA Corps. I must admit that I was largely unfamiliar with them before joining the Thomas Jefferson.

The NOAA Corps as we know it today began in 1970, though its roots are much older. As president, Thomas Jefferson (for whom NOAA Ship Thomas Jefferson is named) created the United States Survey of the Coast, which would later evolve into the United States Coast & Geodetic Survey. Their early operations were not unlike the survey work that NOAA Ship Thomas Jefferson is doing today, though their tools were more primitive: surveyors wanting to determine the depths of America’s bodies of water didn’t have the benefit of sonar, and instead used lead lines – lead weights tied to the end of ropes. These surveyors would also play a vital role in our military history. They would often assist artillery, and survey battlefields. This is what led to the United States Coast & Geodetic Survey (and later, the National Oceanic and Atmospheric Administration) to gain a commissioned uniformed service. Due to the rules of war, captured uniformed service members could not be tried as spies.

To join the NOAA Corps today, you need to first have a bachelor’s degree. ENS Grant received his degree from Stockton University in Marine Sciences, but he says that it isn’t a requirement that the degree be in a maritime field. He says that some of his classmates had degrees in fields such as English or Communications. After getting a degree, you then apply to join the NOAA Corps (anyone interested should check out this website: https://www.omao.noaa.gov/learn/noaa-corps/join/applying). If selected, you would then complete the Basic Officer Training Class (BOTC), which generally takes about 6 months. After that, you’d be given your first assignment.

Did you know? Before NOAA Ship Thomas Jefferson was operated by the National Oceanic and Atmospheric Administration, it belonged to the U.S. Navy and was known as the U.S.N.S. Littlehales

David Tourtellot: The Speed of Sound, July 15, 2018

Posted on July 17, 2018 by dtourtellot2018

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 15^th, 2018

Weather Data from the Bridge

Latitude: 28° 49.4115’N

Longitude: 93° 37.4893’W

Visibility: 10+ Nautical Miles

Sky Condition: 4/8

Wind: Direction: 240°, Speed: 7 knots

Temperature:

Seawater: 31.7°C

Air: Dry bulb:31.5°C Wet bulb: 27.5°C

Science and Technology Log

NOAA Ship Thomas Jefferson is well underway in its mission of surveying the seafloor. The primary tool that the ship (as well as its 2 Hydrographic Survey Launches) is using to accomplish this task is sonar. Sonar was originally an acronym for SOund Navigation And Ranging. If you are familiar with echolocation – the system that some animals (such as bats and dolphins) use to navigate their surroundings – then you already have a basic understanding of how sonar works. The sonar transmits a short sound (called a ping) that will travel down, away from the ship, until it hits the seafloor. At this point, it will reflect off of the sea floor, and echo back up to the ship, where it is detected by the sonar’s receiver. The crew aboard are then able to calculate the depth of the water.

To make the necessary calculations, there are 3 variables at play: the time that it takes for the ping to travel; the distance that the ping travels; and the velocity, or the speed, at which the ping moves through the water. If we know two of those variables, it is easy to calculate the third.

When using sonar to determine the depth of the water, distance is the unknown variable – that’s what we’re ultimately trying to figure out. To do so, we need to know the other two variables. Time is an easy variable for the sonar to measure. The sonar has a transmitter, which generates the ping, and a receiver, which hears it. These two components communicate with one another to give us an accurate measure of time. The third variable, velocity, is a bit trickier.

In saltwater, sound travels approximately 1500 meters per second. However, that rate can vary slightly based on water conditions such as temperature and salinity (how salty the water is). In order for sonar to get as accurate a reading as possible, it needs to calculate the precise speed of sound for the particular water it is in at the moment. The sonar is able to do that by using a component called a sound velocity sensor, known colloquially as a singaround.

The sonar on the hull of one of the Hydrographic Survey Launches. The orange rectangles are the projector (or, the transmitter) and the receiver, and the component in the green circle is the singaround

A singaround looks like a bar with a nub on each end. One nub is a projector, and the other is a reflector. The projector broadcasts a ping that travels parallel to the hull of the ship, bounces off of the reflector, and returns to the projector. We use that information to calculate velocity. The calculation uses the same 3 variables as above (time, distance, and velocity), but this time, distance isn’t the unknown variable anymore – we know exactly how far the ping has traveled, because we know how far the projector and reflector are from one another. The singaround electronically measures how long it takes for the ping to travel, and since we now know two of the variables (distance and time) we can calculate the third (velocity) for our particular water conditions at the face of the sonar.

Sound travels roughly 4 times faster in water than it does in air (this is because water is denser than air). To ensure that the sonar gets an accurate reading, it is important that air bubbles don’t get in the way. The boat’s hull (bottom) has a triangular metal plate directly in front of the sonar, which routes air bubbles around to the side of the sonar.

The hull of one of the Hydrographic Survey Launches.

Personal Log

Each day, the ship’s CO (Commanding Officer) publishes a POD, or Plan Of the Day. This is full of important information – it tells us what the ship will be doing; if/when we will deploy the launch boats, and who will be on them; what time meals will be; and the expected weather conditions. Below is an example from Friday, July 13^th.

NOAA Ship Thomas Jefferson Plan of the Day for Friday, July 13, 2018

On Friday, I had the opportunity to go out on one of the Hydrographic Survey Launches. Because of their smaller size, the launch boats are great for surveying difficult to maneuver areas. For instance, we spent most of the day surveying an area near an oil rig, and were able to get much closer than the Thomas Jefferson could.

Survey Tech Mike Hewlett collecting and analyzing survey data aboard a launch boat

An oil rig and a supply vessel

I’ve been very impressed by how multi-talented everyone on the ship seems to be. In addition to analyzing data, the ship’s survey techs can also be found handling lines as the survey boats are launched and recovered, and do a lot of troubleshooting of the hardware and software they’re using. The coxswains (people who drive small boats) double as engineers, fixing issues on the launch vessels when away from the ship. I’m surrounded by some very gifted people!

Coxswain Francine Grains and Survey Tech Brennan Walters fixing the air conditioner on one of the launch boats that had stopped working unexpectedly. They had it up and running in no time

Did you know?: As president, Thomas Jefferson ordered the first survey of the coastline of the United States. Because of this, NOAA Ship Thomas Jefferson is named for him.

Latest Highlight: While surveying, we spotted a water spout in the distance. A water spout is a tornado that forms over water. Luckily, we were a safe distance away. It was an amazing sight to see!

Brandy Hill: First Leg (hopefully not the last!) at Sea Complete: July 12, 2018

Posted on July 12, 2018 by bhill2018

NOAA Teacher at Sea

Brandy Hill

Aboard NOAA ship Thomas Jefferson

June 25, 2018 – July 6, 2018

Mission: Hydrographic Survey- Approaches to Houston

Geographic Area of Cruise: Gulf of Mexico

Date: July 12, 2018

Personal Conclusion

It was wonderfully impressive listening to ENS Jacquelyn Putnam’s orders to the Bridge while docking the ship. She and Lt. Klemm stood just outside the doors to the Bridge with a clear view of the dock at Pier 21. As she called out orders, the Bridge team would respond by making adjustments to the rudder, speed, or direction. I hadn’t realized how much of a team effort docking the ship would be. It was like parallel parking a car in busy downtown Portland on a much larger scale.

We arrived at Pier 21 in Galveston, Texas early Friday morning on July 6th. There were several fishing vessels flocked with birds. Sometimes you could see dolphin fins peeking up through the water around the boat.

After we were safely docked, all shipmates met in the mess where CDR Chris van Westendorp gave a speech of recognition and appreciation for his crew. These last couple legs at sea are especially meaningful for CO as they symbolize a transition of many years at sea to an upcoming land assignment. There were also several people taking much-deserved leave, or moving onto other job assignments.

Sunset from the bow during my two weeks aboard NOAA ship Thomas Jefferson.

I am so grateful to have been able to participate as a teacher at sea on the Thomas Jefferson. I knew it would be a learning experience, but I didn’t realize how impactful my relationships and interactions with the crew would be. There is something truly inspirational about being around a well-functioning team of people serving a meaningful purpose. People are excited to work for NOAA and to be a part of a higher scientific mission.

I also hadn’t realized the direct relationship between hydrographic surveys and hurricane relief. After a hurricane, the sea floor can shift and change/block major pathways for delivering supplies like oil and water. Last year, NOAA ship Thomas Jefferson responded to Hurricane Maria in Puerto Rico, “NOAA Ship Thomas Jefferson spent the last three weeks in Puerto Rico and the U.S. Virgin Islands surveying ports and bays in response to Hurricane Maria. Over the three week period, the crew surveyed 13 areas and no fewer than 18 individual port facilities, as well as conducted emergency repairs to three tide and weather stations.” (NOAA Office of Coast Survey, October 2017)

Looking towards next school year, I am excited to bring my experience into the classroom and provide students with meaningful learning opportunities. I am looking into using Citizen Science, ways of incorporating the Ocean Literacy Principles, and reaching out to have more diverse professionals interact with my classroom. One of my goals as a science and math teacher is to provide students with many opportunities to ask questions, explore, think critically, and be inspired to continue a lifelong journey of learning and growth.

My experience with NOAA and NOAA ship Thomas Jefferson will forever have an impact on my classroom and for that, I am extremely grateful.

4th of July goodies made by ENS Sydney Catoire, Julia Wallace, and Kevin Brown.

I practiced my Bowline knots on the long trek home.

David Tourtellot: Out To Sea and Gathering Data, July 11, 2018

Posted on July 12, 2018 by dtourtellot2018

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 11, 2018

Weather Data from the Bridge

Latitude: 28° 51.29’N.

Longitude: 093° 44.54’W

Visibility: 10+ Nautical Miles

Sky Condition: 6/8

Wind: Direction: 285°, Speed: 4 knots

Temperature:

Seawater: 30° C

Air: Dry bulb: 30.1°C Wet bulb: 26.8°C

Science and Technology Log

NOAA Ship Thomas Jefferson is currently anchored in the Gulf of Mexico, approximately 50 miles Southeast of Galveston, Texas. The ship is on a hydrographic mission, meaning it is in the process of mapping an approximately 1100 square nautical mile area in order to make updated nautical charts. These will be very useful for ships as they approach the Port of Houston, which is one of the busiest ports in the world.

NOAA Ship Thomas Jefferson carries 2 smaller survey vessels (also known as Hydrographic Survey Launches, or HSL’s) that assist in our research. These boats carry sonar systems (which I will go into greater detail about in a future blog post), as well as some other devices that are used to make various measurements. I was fortunate enough to be able to go out on one of these smaller boats as they collected a variety of data.

One of the small survey boats near NOAA Ship Thomas Jefferson

One device that is used is called a CTD. The name is an acronym, standing for conductivity, temperature, and depth. Conductivity refers to how well the water conducts electricity. That data can be used to determine the salinity of the seawater, or how salty it is. If a scientist knows the salinity and temperature of the water, they can determine the density of the seawater.

Kevin Brown putting a CTD into the water

Additionally, the boats carry devices that collect samples of the sea floor. The makeup of the seafloor varies greatly from one location to another – some areas are sandy, while others are rocky or muddy. This information can give mariners a better idea of what the underwater habitat is like, and is some of the most sought after data that NOAA Ship Thomas Jefferson is collecting.

Mud collected from the sea floor

The bottom sample that we collected was mostly mud. In addition to recovering a physical sample, the crew is experimenting with taking a photo of the seafloor using a GoPro camera. When I was on board, they had successfully mounted the camera to the bottom sampler, but were unable to get a good image.

Personal Log

Port side view of NOAA Ship Thomas Jefferson docked in Galveston, TX, where I got on board.

I arrived in Galveston, TX, on the morning of July 8th, which was a Sunday. I found the ship to be mostly empty, as most of the crew had gone into the city. I was greeted by ENS Garrison Grant, who gave me a tour of the ship. The ship left port on Monday afternoon, and it was fascinating watching the crew on the bridge navigate out into open water. The lanes going into Galveston and Houston were very busy with a wide variety of vessels – I saw everything from small fishing boats to huge container ships and cruise ships. Safe navigation requires clear communication and lots of attention to detail. I imagine that it could be quite stressful, but the bridge crew were all calm and professional.

Yesterday, we did two safety drills – the first was a fire drill, and the second was an abandon ship drill. The general principles of these drills are very similar to what we do at school – we make sure that every individual knows where they are supposed to be and what role they are supposed to play in an emergency situation. Hopefully we won’t need to put that knowledge to use, but practicing these procedures is essential to crew safety in the event of an emergency.

In the event that the crew needs to abandon ship, all of us will don survival suits before going to the life raft.

I’m delighted to say that I have found the crew to be very friendly and helpful – they’re very patient with me and good at explaining their complex systems in easy to understand terms, for which I am very grateful.

Before I left Missouri to join the ship, my friends, students, and colleagues asked me dozens of questions, but probably the most frequent one was about the living arrangements on board. I didn’t know what to expect, and I have found the stateroom I’ve been assigned to be quite pleasant. The room is equipped with a comfortable bunk bed, a small television, a refrigerator, and an en-suite bathroom. There are also a pair of desks and ample storage room.

The stateroom I am staying in while aboard the ship

Did you know?: When measuring the temperature of the air, NOAA Ship Thomas Jefferson uses both a dry bulb thermometer and a wet bulb thermometer. The difference between the two allows us to determine the relative humidity of the air.

Highlight of the Day: Yesterday, while aboard the small boat, I saw several dolphins playing in the water. I’ve never seen dolphins in person before, so it was really cool getting to watch them.

David Tourtellot: Introduction, July 5th, 2018

Posted on July 6, 2018 by dtourtellot2018

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 5, 2018

Personal Introduction: Greetings! My name is David Tourtellot, and in just a few days I will be joining the crew of NOAA Ship Thomas Jefferson as part of the Teacher At Sea program. I feel very fortunate having been chosen for this opportunity, and I couldn’t be more excited!

I received a degree in Music Education from the Conservatory of Music and Dance at the University of Missouri – Kansas City, and I just finished my fifth year teaching 5th and 6th grade orchestra classes at 4 elementary schools in Lee’s Summit, Missouri. We had a great year making music together!

David Tourtellot

I have long been fascinated by the field of acoustics, and I share that with my students. Not only do they learn the fundamentals of playing music, we also discuss how their instruments make sound, the properties that make one instrument sound different from another, and why our ensemble sounds different performing in one room than we do in another. Currently, NOAA Ship Thomas Jefferson is doing a hydrographic survey and is using sonar (which operates using sound waves) to detect what is underwater. I am very much looking forward to learning more about this, and helping my students to make deeper connections between science and the arts.

At the National Weather Service Forecast Office in Pleasant Hill, Missouri

I’m also looking forward to spending time on the ship. I’ve lived my entire life in the Midwest, and can count the number of boats I’ve been on on one hand. This will certainly be a new experience!

Brandy Hill: Weather Reports and Rock Hunting, July 5, 2018

Posted on July 5, 2018 by bhill2018

NOAA Teacher at Sea

Brandy Hill

Aboard NOAA ship Thomas Jefferson

June 25, 2018 – July 6, 2018

Mission: Hydrographic Survey- Approaches to Houston

Geographic Area of Cruise: Gulf of Mexico

Date: July 5, 2018

Weather Data from the Bridge

Latitude: 28° 53.4’ N

Longitude: 093° 44.6’ W

Visibility: 10+ NM

Sky Condition: 3/8 (Reminder: 3 out of 8 parts of the sky are covered with clouds.)

Wind: 6 kts

Temperature:

Sea Water: 29.1° C

Air: 27° C

Science and Technology Log

It is fitting to add a section on weather because tonight we are seeing a lightning storm! I can even hear the fog horn. During Bridge Watch, weather data is logged every hour around the clock. Every four hours, it is entered into a computer system. On most days, we are fortunate to get a weather report in various character voices over the intercom from ENS Krabiel.

This is the hourly weather log from June 26, 2018.

My favorite tools are the wind wheel, alidade, and relative humidity thermometers.

A somewhat complicated process allows one to find the true direction (opposed to relative) of the wind. Since the ship is not always traveling North, it is important to be able to calculate true wind direction. Officers typically use a reading on the computer to find true wind direction, but I thought it was a neat tool to try.

The alidade is located outside of the Bridge. It is a sighting device used for measuring angles. It has been helpful with measuring the swell direction. ENS Krabiel mentioned that it is also useful for checking bearings when a ship is anchored. For example, a bearing (like to an oil platform in the Gulf of Mexico) will change if the ship is drifting and/or dragging anchor.

On the Weather Log, there is a place for “dry bulb” and “wet bulb.” This information is collected using two thermometers outside of the Bridge. The dry bulb is a typical thermometer, while the wet bulb has a small sock-like covering wicking up water from a tray. The closer the two temperature values, the higher relative humidity.

I have also sat in on a number of data processing evenings with the Survey Team. In one evening, roughly 50 GB of data from multibeam sonar only was processed. It is estimated that a total of 11 TB has been processed since April. Data processing begins around 7:30 pm and the survey team analyzes all information collected during the hours of 7am- 7pm. Staying on top of processing is important because of the massive amounts that accumulate, especially from side scan sonar.

Julia Wallace, physical scientist, showed me one aspect of processing multibeam sonar. She takes a file of data and runs a “flier finder” with a parameter of 0.5 meters (appropriate for the depth of sonar.) Essentially, the flier finder is marking any outliers that fall outside of this range. Julia then manually goes through and “hides” these points so that they do not contribute to the data set. This is important because when this data is used to mark bathymetry (sea floor depth) on nautical charts, it will somewhat randomly “grab” these false sounding set numbers and could land on one of the outliers, resulting in a false depth.

Every dot in this picture of raw data is a sonar ping returning to the multibeam echosounder. The number of pings depends on the sonar sounding frequency. For example, one could expect 300 pings per second when operating at a sounding frequency of 300 hz.

From what I have witnessed and gathered through multiple conversations with the team, the data collected by the Thomas Jefferson for NOAA charts is extremely accurate. For example, every pixel (or node) on the multibeam sonar grid represents no coarser than 1 square meter of the sea floor. This has changed from about 30 years ago where the ratio was 1 nodel: 5 square meters. In addition, many processes are doubled-up as a check for validity. This includes crosslines for checking main scheme data and operating two multibeam frequencies at the same time.

One of the benefits to running two frequencies of multibeam is the ability to create an overlapped average of the two backscatter signals (with a false color scheme.) This information helped inform Lt. Anthony Klemm and survey technician Kevin Brown determine eight unique sites varying in backscatter intensity for bottom sampling. (Remember: intensity is a measure of how strong the sonar ping returns, depicting varying sea floor substrate.

The use of this technology paid off! All eight sites sampled varied in texture and sediment size. Using this process of selectively choosing sites of interest based on “multispectral” backscatter intensity has replaced taking numerous random bottom samples using a grid. Again, this is a highly accurate and time-saving process. It was also interesting seeing the actual sea floor that we are mapping.

In the bottom right corner, Bottom Sample #1 site is selected.

CHST Allison Stone manages the crane while Lt. Charles Wisotzsky directs the bottom sample claw and ENS Taylor Krabiel performs various substrate tests.

ENS Krabiel gives me a tutorial on bottom sampling. Krabiel enjoys creating short “Rock Hunting” clips for entertainment. His enthusiasm has made this trip a lot of fun.

All of the eight bottom sample sites had a different composition. One in particular had a lot of rocks and shells. The rock in the upper right appears to have remnant tunicate casings.

Notes from survey sheet H13044, BS# 001 (Bottom Sample #1) state the grain size: silt, muddy, coarse, and some shell fragments.

A GoPro is located in a cage on the bottom sample claw. Video footage of the sea floor enables hydrographers to view the substrate and current ripples in the sand. ENS Krabiel wears the control on his wrist to activate the camera.

Personal Log

I have enjoyed hearing the back-stories of the crew. For example, Allison Stone, Chief Survey Technician knew she wanted to be a part of NOAA when she was in 6^th grade- the same age as my students. She remembers going to a parent career night at school and speaking with a presenter from NOAA. The presenter was enthusiastic about their job which inspired Allison to pursue a placement with NOAA. Although she envisioned counting marine animals and snorkeling daily, she is still passionate about her work in hydrography geoscience and speaks highly of NOAA outreach.

Field Operations Officer, Lt. Anthony Klemm started out wanting to do a public service and became a teacher. Later, he joined the NOAA Corps and after completing basic training got a job at the Marine Chart Division in Washington DC. It was during this time that he was given a lot of flexibility and time to create and test his own ideas and experiments. In his words, some of them flopped. However, one idea that has recently captured attention is the idea of “crowdsourcing” bathymetry. Collecting, processing, and submitting data for the official approval and update of NOAA nautical charts is a long process. It can take months for charts to be updated and available to the public. Crowdsourcing bathymetry is a way for the general public to gather and submit sonar data using simple devices like a “fish finder” that one might find on a recreational boat. These could serve as interim bathymetry data until the areas can officially be surveyed and charted. It’s also simple (users select a setting), and free.

Visit the NCEI/IHO Data Center for Digital Bathymetry to view digital bathymetry data.

You can read more about this program at:

https://noaacoastsurvey.wordpress.com/2018/05/31/noaa-announces-launch-of-crowdsourced-bathymetry-database/

active captain shoaling hazard fl 2.PNG

This photo and thee above are snapshots of data collected using “crowdsourced” bathymetry.

Peaks

+ Participated in a simultaneous medical/fire drill.

“This is a drill, this is a drill. There has been a medical emergency on the starboard stairway of the bridge…” The person in this picture is only acting and not actually injured. The bridge had also simulated a fire which interfered with steering and communications.

A debrief was held in the Mess after the drills.

This was a day for drills. The FRB (Fast Rescue Boat) was manually unloaded using a hand brake to simulate loss of power. Earlier in the day, the launch boat was manually loaded back onto the ship. Passengers (including myself) boarded the ship using a rope ladder.

NOAA Teacher at Sea Blog

Tag Archives: NOAA Ship Thomas Jefferson

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

David Tourtellot: Draggin’ The Line, July 21st, 2018

David Tourtellot: The Speed of Sound, July 15, 2018

Brandy Hill: First Leg (hopefully not the last!) at Sea Complete: July 12, 2018

David Tourtellot: Out To Sea and Gathering Data, July 11, 2018

David Tourtellot: Introduction, July 5th, 2018

Brandy Hill: Weather Reports and Rock Hunting, July 5, 2018