seafloor mapping – Page 15 – NOAA Teacher at Sea Blog

July 1, 2007April 1, 2021

Beth Carter, July 1, 2007

NOAA Teacher at Sea
Beth Carter
Onboard NOAA Ship Rainier
June 25 – July 7, 2007

Mission: Hydrographic Survey
Geographical Area: Gulf of Esquibel, Alaska
Date: July 1, 2007

Weather Data from Bridge
Visibility: 4 miles
Wind direction: calm
Wind speed: calm
Sea wave height: none
Swell water height: none…flat, flat, flat
Seawater temperature: 12.2 degrees C
Sea level pressure: 1016.6 mb
Dry bulb temperature: 12.2 degrees C; Wet bulb temperature: 11.7 degrees C
Cloud cover: Fog, cloudy, 8/8
Depth: 18 fathoms,
New anchorage: near Sonora Island, part of Maurelle Island group

This is a single beam transducer on the hull of launch #1. The small blue oval on the hull is a “fish finder” or depth sounder. — This is a single beam transducer. The small blue oval on the hull is a “fish finder” or depth sounder.

Science and Technology Log

On Friday, I went out on the RA-1 boat with Coxswain Leslie Abramson, Seaman Surveyor Corey Muzzey, and Survey Tech Marta Krynytzky. The #1 boat is a jet boat, which operates like a jet ski…it has a nozzle that shoots water out, and it only draws one foot of water. The RAINIER likes to use the #1 boat in very shallow water, as it is able to get into shallow places without running aground. #1 is also has a single beam sonar, which means it is sending out “pings” in a single direction directly underneath the boat. Thursday night, Marta drew a grid of lines for the RA-1 to survey. The FOO (Field Operations Officer) asked her to develop a tight grid, with the lines being only 5 meters apart. If you have driven a boat, you know that this means that as you go up and down the parallel lines, your turning ratio is quite tight, and there will be wake and bubbles formed. The problem with this is that bubbles throw off the single beam sonar, and it “scrambles” the feedback from the sea floor.

This is the Echosounder machine that records the data from the single beam transducer.

We were operating in Warm Chuck Inlet, which has some freshwater creeks feeding it. Marta taught me to do a little part of the recording on the Echosounder machine, which is called doing “paper control.” She tracked our progress on her computer, and when we were over an area that needed to be mapped, she would say, “Start recording,” and I would hit a button that started the paper moving. The machine creates a line graph similar to that a seismograph might create during an earthquake, or in a medical scenario, it is similar to that of an EKG that graphs the activity of your heartbeat. When we ran through our own bubbles, it created dense gray shaded areas that obscured the data. We had to slow down, and change our course several times to allow for which way the tide was flowing so that tidal movements would carry our bubbles away from the next line we wanted to drive.

The single beam technology is rather outdated, and NOAA prefers to use the multibeam, as it creates real-time, 3-D pictures of the ocean floor. However, the multibeam transducers are very expensive, and very vulnerable to damage caused by running aground, and so the RAINIER uses both technologies to get as much information as possible without damaging or destroying the multibeams. After we returned to the ship, the RAINIER weighed anchor and moved to a new anchorage near Sonora Island in the Maurelle Islands group.

This is a sample of the paper “picture” of the bottom recorded by Launch #1. — This is a sample of the paper “picture” of the bottom

Personal Log

Friday was an interesting day, as most of the time, I was helping Marta with the recording. I goofed up a few times, as you have to stay so focused and attend to detail constantly. The survey techs have my true admiration…they go out day after day in cool to cold weather, rain or fog or drizzle, and collect intensely detailed data. There are no days off on the ship, really. Actually, everyone on the RAINIER is amazing with his/her ability to focus and stay on-task and get jobs done…from the cooks (who are great!) to the deck crew to the officers to the engineers. Last night (Saturday), Raul Quiros was fishing and caught a small shark…maybe 2 feet long. He cut him off the line, and had a bit of trouble picking him up to release him. The shark was gasping, so I tentatively grabbed his belly and threw him over the side. Then, a few of us saw some whales playing off the starboard side of the ship. I ran and got my videocam…finally! I actually got some footage of a whale! He was rolled over on his back, and slapping the water with both fins, over and over and over. It was amazing. Some people say whales breach and do these “slaps” to remove barnacles, but it looked to me as though he was just having fun!

Question of the Day

Go to the website and click on the “movie” on multibeam surveying. What do you think would happen if the boat passed over a whale or a sunken ship? What would NOAA do with information on sunken ships if they discovered some?
For my first graders: Look at a picture of a humpback whale and a jet plane. Can you see any ways that they are alike? Also, try that website in #1…the movie is definitely something you will understand!

June 29, 2007April 1, 2021

Beth Carter, June 29, 2007

NOAA Teacher at Sea
Beth Carter
Onboard NOAA Ship Rainier
June 25 – July 7, 2007

Mission: Hydrographic Survey
Geographical Area: Gulf of Esquibel, Alaska
Date: June 29, 2007

Weather Data from the Bridge
Visibility: 8 miles
Wind Direction: Light
Wind Speed: Aires
Sea Wave Height: None
Swell Wave Height: None
Seawater Temperature: 12.8 C
Dry bulb Temperature: 13.3 C, Wet Bulb Temperature: 12.2 C
Sea level Pressure: 1009.4 mb
Cloud Cover: Cloudy, light rain, 8/8
Depth: 31 fathoms

ENS Meghan McGovern and Elishau Dotson are recovering the CTD. After recovery, Elishau connects the CTD to her computer and downloads the readings on temperature, conductivity (a function of salinity), and depth. NOAA uses Wilson’s Equation of Sound Velocity to convert the CTD information to something usable in the software — ENS Meghan McGovern and Elishau Dotson are recovering the CTD. After recovery, Elishau downloads the readings on temperature, conductivity (a function of salinity), and depth. NOAA uses Wilson’s Equation of Sound Velocity to convert the CTD information to something usable in the software

Personal Log (Just have to tell you about the whale first!)

On Thursday, Aug. 28, I went out on the #4 launch from the RAINIER. When the hydrographic team goes out, they go out for the whole day…8:15 until 4:30 p.m. It was sunny and clear, our first sunny day! I went out with ENS Meghan McGovern, Elishau Dotson, Assistant Survey Tech, and our pilot, Jodie Edmond, Able Bodied Seaman – an all female boat crew! First, I have to focus on the wildlife that we saw – it was totally incredible! We saw several sea otters floating on their backs, whiskery and cute! We saw a doe leading her two fawns on the shore of an island. Eagles soared overhead all throughout the day, and one dove to catch a fish (missed), but later, he grabbed one in his talons. We got a quick glimpse of a mother harbor porpoise and her calf feeding near the shore.

The highlight of the day, though, was seeing a humpback whale breaching near the boat – to say that I was totally enthralled is not adequate. I don’t think the dictionary has any words that truly fit! First, I saw a silver/gray shape under the water near the stern, and thought it was a stingray, a common sight on the East Coast. Then, I heard a gasp/blow as the whale surfaced to breathe. The sound was like the “grunt” that Monica Seles makes as she serves up a tennis ball, only lower and longer. We saw the whale surface a few more times, and then his great leap. I was trying to videotape, and of course, I missed it. But it will stay in my memory forever, if not on a memory card.

Science and Technology Log

This is the multi-beam transducer mounted on the hull of the #4 launch of the RAINIER. It can produce a broad band of sounds to “ping” off the bottom of the sea, and provide the data to create a 3-D picture of the ocean floor under and near the boat. — This is the multi-beam transducer on the hull of the #4 launch. It can produce a broad band of sounds to “ping” off the seafloor and provide the data to create a 3-D picture.

Now, to focus upon the hydrographic mission! Before beginning the surveying, the crew lowers a CTD to the sea floor to collect a reading on the Conductivity, Temperature, and Depth of the water. The way that the sonar “pings” travel through water is affected by all three factors. The higher the percentage of salinity, the greater is the ability of the water to conduct sound waves. Higher temperatures also increase sound conductivity in water, and deeper water also conducts sound waves better than shallow water. For example, if the launch is surveying the sea floor in an area near where a freshwater creek is flowing in, the conductivity of the water would decrease; therefore, the survey tech crew that does the night processing of the data would be able to correct the resulting data taking into account the lower conductivity. Number 4 launch has a multibeam sonar transducer mounted on the hull. The transducer produces a broad band of sound “pings” that bounce off the sea floor and return to the launch to be recorded by a sophisticated computer with four screens. The operator of the sonar equipment can see a digital display of the depth, and a real-time three-dimensional picture of the sea floor beneath and around the launch. The boat driver is constantly aware of the depth, so as not to run the launch aground on rock formations.

Elishau is monitoring the real-time data streaming in from the transducer as Jodie drives the “lines” to create pictures of the ocean floor.

The driver steers the boat along a pre-set grid of lines that are programmed into the ship’s computer the night before. Jodie said it is rather like “mowing the grass,” on the surface of the water. You “mow” the water in neat rows until you’ve mowed over every line on the chart established by the hydrographers. After all the lines were run, we returned to the ship, and then, other hydrographic scientists began to run a correction program on the data we gathered. In this way, they clean out errors that are caused by extraneous noises, kelp, echoes, and other obstacles. In the afternoon, we were “snagged” by a gigantic clump of kelp that got wrapped around the transducer. There was so much kelp, the launch could not maneuver effectively. ENS McGovern stabbed the kelp with a boat hook, and Jodie reversed the engines until we shook the kelp loose. Learn more about seafloor mapping here.

Questions of the Day

Later that night, Martha Hertzog, Physical Scientist, looks at the data from the #4 launch, and applies a correction program to the data to eliminate errors. The night processors often work until 11:00 p.m. in order to process the day’s data collections from the 3-4 launches that were out that day. — Later that night, Martha Hertzog, Physical Scientist, looks at the data and applies a correction to eliminate errors. The night processors often work until 11:00 p.m. in order to process the day’s data collections.

These questions are particularly for Ms. Southgate’s oceanography students at Hoggard High School in Wilmington, N.C. (and any other curious people!)

I’m learning that salinity affects conductivity of sound waves. Why does a high concentration of salt in water make sound travel faster? Does electricity travel faster or slower through fresh and salt water? Why?
As we drove different lines yesterday, we took three different CTD readings? Why do you think the hydrographers felt we should collect data three times?
The islands here are very craggy and steep, and made up largely of granite and limestone rock. Much of the sea floor is also rock. Why is the coast of Alaska so vastly different to America’s Eastern coast?
The islands here drop very sharply off into deep water. For example, just 3-4 meters from shore, the depth can drop to 20 meters. Why is this common here? How much is 20 meters measured in feet? In fathoms?

June 27, 2007April 1, 2021

Beth Carter, June 27, 2007

NOAA Teacher at Sea
Beth Carter
Onboard NOAA Ship Rainier
June 25 – July 7, 2007

Mission: Hydrographic Survey
Geographical Area: Gulf of Esquibel, Alaska
Date: June 27, 2007

Weather Data from Bridge
Visibility: 6 miles
Wind direction: 034 degrees
Wind speed: 5 mph
Sea Wave Height: none
Swell Wave Height: none
Seawater temperature: 12.2 degrees C
Sea level pressure: 1017.2 mb
Dry Bulb Temperature: 12.2
Wet Bulb Temp: 11.7
Cloud cover, type: 8/8, stratus and cumulus
Depths: 31 fathoms

Researchers are kneeling in a sitka spruce forest as they check the computer that is collects and records tidal data on a small island in Nossuk Bay, Alaska. — Researchers are kneeling in a Sitka spruce forest as they check the computer that is collects and records tidal data on a small island in Nossuk Bay, Alaska.

Science and Technology Log

On Tuesday afternoon, June 26, I went out with a crew of researchers to check the equipment that collects tidal data for Esquibel Bay. There are six main pieces of equipment used to collect this data: 1) a cylinder of nitrogen, 2) a hose attached to the nitrogen cylinder that emits small bubbles of nitrogen into the water, 3) a computer that collects and records data, 4) a solar collector to power the computer’s battery, 5) a transmitter that sends the data to a satellite, and 6) the tide staff (an actual wooden staff in the water), and GPS benchmarks. The staff is set and readings taken so that the vertical measurements of the staff are linked to the benchmarks. The gage, which is officially a “tertiary” gage, is set up concurrent with a “primary” gage that has been acquiring data for over one epoch (19 years or more). Sitka, Alaska, is the site of NOAA’s primary gage, which has similar tidal characteristics to the area that we are working now. Thus, only an amplitude and phase differential must be applied to the Sitka gage to get a water level for this area. Without the staff readings, there would be no way to tie the “bubbler” level to the ground surrounding the gage site, and thus no way to recover the actual local vertical datum (water level) relative to the gage in Sitka.

The nitrogen cylinder slowly leaks bubbles through the hose, which are released into the water. When the tide is high, there is more water and pressure above the hose which makes it more difficult for the bubbles to escape the hose. When the tide is low, there is less water above the hose, and therefore less pressure, which makes it easier for the bubbles to escape. Readings are recorded digitally every six minutes, averaged every six seconds. Staff-to-gage measurements are also recorded every six minutes whenever the site is visited, and 3 hours’ worth are recorded at installation and removal, so that the vertical measurements of the station are effectively “tied” to the measurements at the primary water level station at Sitka. (Good Working Question: Download data from both stations and compare the two – are there differences? Next, compare Sitka and Ketchikan and Kodiak – are there bigger differences?).

ENS Meghan McGovern, Junior Officer of RAINIER, and Shawn Gendron, survey technician, position the tripod which will hold the transmitter to collect the GPS information needed by the RAINIER.

For some reason, the transmitter is not emitting signals that can be read by the satellite, and therefore by the scientists at NOAA headquarters. This is why the skiff took several technicians over to check the equipment to see if it is still functioning and recording properly. They downloaded the water level data to send to headquarters via email while also setting up GPS equipment so that an ellipsoidal (GPSrelative) height can also be linked to the orthometric (gravitational) elevation determined through water level measurement, and will return to the ship and process the GPS data. The tides are important to hydrographic surveying, because obviously, the water is deeper at high tide than at low tide. The goal is to collect accurate information on tides, and then combine that with the data collected by the launches, in order to get accurate depth information. The tide-corrected depths on the chart they want to show are relative to the mean low low water, which is the average of the lowest of daily tides taken over the last 19 years. On the Atlantic Ocean, tides are semi-diurnal. This means that there are two high tides and two low tides per 24 hours. But, on the Northeastern Pacific, tides are mixed. See here for more details.

Today, (Wed. June 27), the crew returned to the small island to check on the HorCon station, which stands for Horizontal Controls. The RAINIER established this water level station in April of 2007, and set into place 5 benchmarks which are tied into the international framework of benchmarks that make it possible to utilize GPS, or Global Positioning Satellites to determine one’s exact location. RAINIER’s researchers placed a receiver antenna on top of a tripod, which was positioned exactly above the center of the metal disc benchmark cemented into a rock. The antenna receives from some of the 11 Global Positioning System satellites that orbit the earth and constantly change their relative positions. For a final position to be accurate, at least four satellites must be recorded in two different sessions of more than six hours duration separated by at least one day. They connected the cables, turned on the GPS receiver and then waited for the satellite constellation (also known as the ephemeris) to be downloaded so that all available satellites could be tracked. The first satellite was tracked around 1 hour later, and then we left the island, as the equipment was to be left in place for at least 6 hours. When we returned 6 hours later, 8 satellites had made contact, and the recordings were noted and will be taken for evaluation onboard the ship.

Anna-Liza Villard-Howe, the Navigation Officer of the RAINIER, explained to me that the GPS measurements of benchmarks are being conducted in order to get as precise a determination of sea level as is possible, so that all the hydrographic information collected by the RAINIER can be referenced to the ellipsoid. Sea level has changed in Alaska in the recent past due to glacial rebound, which means that as the glaciers recede, the land is actually rising. Also, many large earthquakes have occurred in Alaska in the last century, which also changed the shape of some landforms and affected sea level readings. Online Sea Floor Mapping Activity Targets Kids (CED, OCS). In celebration of World Hydrography Day, NOAA’s Ocean Service Communications and Education Division, in cooperation with NOAA’s Office of Coast Survey, launched a new educational offering — Sea Floor Mapping — on the National Ocean Service Education Web site. It is designed for students at the 3^rd – 5th grade level, and the media-rich activity teaches young people about mapping the seafloor and why it is important. This activity also conveys information about NOAA’s missions of discovery and service. The Sea Floor Mapping Activity is available online here.

Questions of the Day

Why are tides in the Pacific and Atlantic different? What are the factors that affect tidal changes?
Look up a tidal chart for the inlet or beach nearest to your home. How far apart are the high and low tides?
Who (which country or countries/which agencies) is responsible for the maintenance of the 11 Global Positioning Satellites that are now orbiting the earth? If a satellite fails, would it be replaced? By what agency?

Personal Log

While on the tiny island, one of the officers carried a shotgun…in case we met a bear! I’m pleased to say we didn’t encounter a bear, but did discover animal scat, and two eagle feathers. One was a tail feather – beautifully white – and we didn’t collect the feathers because it is illegal to collect eagle feathers. We also saw 7-8 harbor seals on a rock outcropping. We tried to sneak up on them to get good photographs, but they bobbed and rocked and slipped into the water before we got very close. Also, on the island I was surprised to find many clumps of saltwort, which Eastern coast students (and my first grade class!) should recognize from the mud flat near the salt marsh. It tastes….salty! No surprise there.

On Wednesday, there were so many white gnats that we sent the skiff back to the ship for bug repellant. They were like No-See-Ems, only we could See Em and Feel Em! We built a small, smoky fire, which made things somewhat better. The highlight of the day for me was kayaking after dinner with the XO (Executive Officer) of the ship, and Ian Colvert, an assistant survey technician. We saw a rainbow and paddled through a misty rain, then sunshine…a beautiful evening.

June 24, 2007April 1, 2021

Rebecca Himschoot, June 24, 2007

NOAA Teacher at Sea
Rebecca Himschoot
Onboard NOAA Ship Oscar Dyson
June 21 – July 10, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific Ocean, Unalaska
Date: June 24, 2007

Weather Data from Bridge
Visibility: less than .5 nm (nautical miles)
Wind direction: 260° (SW)
Wind speed: 18 knots
Sea wave height: 4-6 foot
Swell wave height: 0 feet
Seawater temperature: 2.9°C
Sea level pressure: 1006.0 mb (millibars)
Cloud cover: fog

Science and Technology Log: What Is the Summer Pollock Survey?

The Alaska Fisheries Science Center (AFSC) is one of six regional centers charged with monitoring commercial fish stocks in the United States. The AFSC is located in Seattle, Washington, however the data the scientists from the Center collect is gathered from coastal areas across the state of Alaska. For over 20 years the AFSC has been surveying Pollock stocks in the Bering Sea of northwestern Alaska in the summer months. More recently they have also been surveying stocks in the Gulf of Alaska during the same season. During the Pollock spawning months of February-March surveys are also conducted in known spawning areas. The AFSC scientists’ data are one part of the fishery management triangle: The summer Pollock survey on the OSCAR DYSON will take place in three sessions of three weeks each. The first day of each leg is spent calibrating the acoustic equipment to make sure it is accurate for the rest of the research in the next three weeks. Once the OSCAR DYSON reaches the Bering Sea, the navigation team locates the transects that have been surveyed in years past. The science team begins collecting acoustic data, and fishing intermittently to collect more data about the fish, such as exact lengths, gender and age information.

The acoustic data are collected every second. Sound waves are emitted from a transducer affixed to the hull of the ship; when these sound waves strike a surface, they return to the transducer. By calculating the time the sound waves traveled it is possible to “see” where the objects are the sound waves bounced off of. The bottom of the ocean shows up as a very strong, solid line, whereas fish in groups show up as “clusters” in the water column (the sound waves bounce off the air-filled swim bladders of the fish). By using different frequencies, the scientists are able to determine if the clusters are larger or smaller fish, including plankton-sized euphausids (i.e., krill). This amazing system for “seeing” fish using sound waves is modeled on the feeding strategies of some of the oldest and best-adapted fishers, the toothed cetaceans such as dolphins and sperm whales.

Personal Log

Luckily the crew of the OSCAR DYSON were able to give me some very good advice about seasickness medication. We entered some moderate seas our first day out, but I’m slowly getting my sea legs. The Bering Sea is a very shallow body of water, less than a hundred meters deep in many places, so that it has a great deal of wave action in any kind of windy weather. Today we passed the Pribilof Islands, but it was too foggy to see them.

Question of the Day

Answer to Day 1 question about solstice: The word “solstice” comes from the Latin words “sol,” which means sun, and “sistere,” which means to rest or relax. The solstice occurs twice each year, when the Sun is at its northern- or southernmost point from the equator. The solstice is the turning point at which we experience either increasing or decreasing increments of daylight (paraphrased from the Encyclopedia Britannica online).

Today’s Question: The scientific method includes controlling the variables in an experiment. What are some examples of variables the science team from the AFSC is controlling in the summer Pollock survey?

August 16, 2006March 26, 2021

Candice Autry, August 16, 2006

NOAA Teacher at Sea
Candice Autry
Onboard NOAA Ship Thomas Jefferson
August 7 – 18, 2006

Mission: Hydrographic Survey
Geographical Area: Northwest Atlantic
Date: August 16, 2006

“Experiences on the Fast Rescue Boat”

TAS Candice Autry prepares to use the CTD instrument which collects water information related to conductivity, temperature, and depth. — Candice Autry prepares to use the CTD instrument which collects water information related to conductivity, temperature, and depth.

Science and Technology Log

Today I had the opportunity to go out on the Fast Rescue Boat (FRB) to use the conductivity, temperature, depth (CTD) instrument in various places in the harbor. The CTD looks like a simple white tube; however, the capabilities of the CTD are far from simple! This devise provides essential data for scientists. Three of us boarded the small FRB, loaded the CTD, and were off to our locations. The first observation noted is that being on the fast rescue boat is a different boating experience compared to the launches and the THOMAS JEFFERSON. The “fast” part of the description is fitting; the boat moves quickly! The main function of the CTD is to collect data about how the conductivity and temperature of water changes relative to depth. Conductivity and temperature information is important because the concentration of the salt of the seawater can be determined by these two changing variables.

Candice Autry holds the CTD instrument. We collected information from three locations; once in the morning and then again in the afternoon.

The CTD devise can also help surveyors determine the speed of sound in the water. The information from the CTD is used in conjunction with multi-beam sonar providing accurate data about the depths of obstructions on the seafloor. The metal frame seen in the picture on the outside of the mechanism is called a rosette. We attached a rope to the rosette of the CTD, turned it on to collect data, held the devise in the water for two minutes for adjustment, then lowered the instrument down to the bottom of the seafloor. Once the CTD hits the bottom of the seafloor, the rope is pulled back up, the devise is put back into the fast rescue boat, turned off, and it is off to the next location to collect data. We deployed the CTD in three different locations in the morning and three different locations in the afternoon. At each place where data collection occurred, the location was recorded by using a global positioning system. Back on the THOMAS JEFFERSON, the information that the CTD collected is downloaded to a computer where specialized software is used to understand the data.

Personal Log

All of the experiences on the THOMAS JEFFERSON have been interesting and fun. Tomorrow I will be helping some of the crew on the deck of the ship. Exposure to saltwater often causes rust to occur; a ship requires constant maintenance! I am also realizing that this adventure will be over soon, with less than two days left. Until tomorrow…..

Senior Surveyor Peter Lewit shares the chart used as a guide for the launches to collect data. The red lines in the white area of the chart represent the paths the launches took to collect data using side scan sonar and multi-beam sonar technologies. — Surveyor Peter Lewit shares the chart used to collect data. The red lines in the white area represent the paths the launches took.