Meg Stewart: Data Acquisition on a Small Boat: Tips and Tricks, July 14, 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 14, 2019

Weather Data from the Bridge
Latitude: 58° 36.7 N
Longitude: 162° 02.5 W
Wind: 9 knots SE
Barometer: 1005.0 mb
Visibility: 10 nautical miles
Temperature: 61° F or 15.5° C
Weather: Overcast with fog, no precipitation

Fairweather in fog
The other day while on a survey launch, we came up on the Ship Fairweather as fog was rolling in.


Science and Technology Log

Launch preparation
A launch getting ready to survey. The setup process takes some time and all of the preparation is necessary for accuracy in the data.
Heave, pitch, roll, and yaw describe the movements of a boat (or a plane). An inertial measurement unit reads those discrete movements. Source: wikipedia

In the last post I talked about hydrographic surveying, the software used and the multibeam echosounder on the survey boats (called launches). The software is setup in the cabin by the hydrographer in charge. It takes a good five minutes to get an accurate read from the GPS (global positioning system) receiver. Then it takes time for the IMU (inertial measurement unit) to respond and start to read the boat’s heave, pitch, roll, yaw, and heading values. 

hydrograpers
The hydrographer in charge (standing) is showing the hydrographer in training (seated) how to setup the day’s survey project using the echosounder software.
launch data storage
The four Fairweather launches have the same, high-end technology in their cabins used to collect data from the multibeam echosounder, CTD sensor, a sound speed system, and a positioning and altitude system.

Often, the launch drives in a circle eight in order for the positioning receivers to be “seen” by the satellites, as a  stationary object is more difficult to detect than one that is moving. Setting up the day’s project using the multibeam echosounder software also takes some time but all the steps need to be done properly and to the correct specifications prior to starting the sounder. If not, the locational data will be wildly off and the depths inaccurate.

Another task that must be done from the launch before starting to transect is to test the salinity and water temperature using a CTD probe, which is called a cast. I mentioned this in a previous post. CTD stands for conductivity, temperature and depth. In the general area where the launch will survey, the CTD drops slowly to the bottom of the seafloor, collecting data that will be fed into the hydrographic program. Salinity and temperature at different depths will slightly change the rate at which sound travels in water. Again, the CTD process makes the location and depths as accurate as possible and must be done.

Meg casts CTD probe
Casting the CTD probe into the survey location to get conductivity, temperature and depth readings.

Usually, the chief hydrographer sets the defined area to be transected for the day and this is usually a polygon. The launch will sweep with the multibeam echosounder the outside lines and then scan at parallel set distances between the lines, either in a roughly north-south direction or a roughly east-west direction. For this particular hydrographic project, coverage of survey lines can be spaced at about 400 meters apart or greater apart depending on the depth. Recall that the nautical chart of Bristol Bay from the last post showed soundings dotting the area. Solid bathymetric coverage is not always needed on these projects. The Cape Newenham area has proven to have gradually varying depths and is mostly quite flat so free from obvious obstructions like large boulders and sunken ships. 

Once the technology setup is complete in the cabin, the hydrographer shares the map window with the coxswain (the person in charge of steering or navigating the boat). The hydrographer sets the points and the lines so that the coxswain knows where to direct the launch. And by direct, I mean the coxswain uses compass direction and boat speed to get from place to place for the survey. And the hydrographer in charge turns the echosounder on and off when the launch is in position or out of position.

Coxswain
The coxswain navigates the survey line set by the hydrographer in charge.

Because the transects run parallel to each other and are equally spaced apart, the hydrographers call this technique “mowing the lawn,” (see video below) for they are essentially mowing the surface of the ocean while the multibeam echosounder is collecting soundings of the surface of the seafloor.

A video of someone mowing a lawn on a riding lawnmower

A day out on a launch will go from about 8:30am to about 4:30pm but sometimes an hour or so later. If the Alaskan weather is cooperating, the hydrographers want to do as much as they can while out on the launch. Once surveying is complete for the day, the hydrographer in charge has to close up and save the project. Then data get transferred to the larger workstations and shared drive on the Fairweather.

Meg on launch
Every day on the launch, at least on this leg, has been great with perfect weather. And today, the added bonus for me was the phenomenal geology as we surveyed right along the shore.


Personal Log

I’ve taken loads of photos and video while at sea. I have tried to post just those pictures that help explain what I’ve been trying to say in the text. I haven’t posted any video on here as the internet on the ship is very weak. These next photos are a tour of different parts of the NOAA Ship Fairweather.

  • view of the bridge 1
  • view of the bridge 2
  • view of the bridge 3
  • barometer

The above slide show gives an idea of what the bridge is like. The ship is steered from the bridge. All the navigational instruments and weather devices, among other tools, are found on the bridge.

emergency billet
These emergency billets are for me, TAS Stewart, Meg, and it’s posted on my door. For each emergency situation, Fire, Abandon Ship, or Man Overboard, there is a bell sound and the location on the ship where I am to muster. Life at sea is all about being ready for anything.
mess
This is the mess (where we eat. And eat. And eat!) The food is fantastic but I’ve gained some pounds for sure.
Ice cream spot
Maybe this is why. Sometimes the Ice Cream Spot looks like this. Ha!
The galley
The galley
Laundry
Laundry machines available and detergent is supplied. No need to bring all your clothes. Also, sheets and towels are supplied.
Stairs
Stairs are called ladders on a ship. Makes sense to me – they’re often pretty steep. You must always hold a rail.
The Lounge
The Lounge
DVD collection
DVD collection of over 500 films
Lounge full of people
Yes, so this is the lounge and there can be meetings in here, training, movies, games, puzzles, quiet space, etc.
DVD in stateroom
Or, you can pop a DVD into a player in the Lounge, go back to your stateroom and watch. Or fall asleep. This is the original Blade Runner (which I never saw) and which I didn’t care for.
Finer things
The good folks of Ship Fairweather like to have a nice time every now and again, so they set up evenings, about once a leg, to have Finer Things. People come by, bring fine cheeses, fine chocolates, fine almonds, fine fig jelly, and fine maple sugar candy from Rhinebeck, NY, and have a fine time. And a disco ball.


Did You Know?

Inertial Measurement Units (IMU) technology that is so important for accurate hydrographic survey mapping was developed by the U.S. military. IMUs were used in the development of guided missiles, unmanned aerial vehicles (and now drones), battlefield reconnaissance, and target practice.

Quote of the Day

“A ship in port is safe, but that’s not what ships are built for.” – Grace Hopper

Brandy Hill: What Lies Beneath the Surface, July 1, 2018

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 1, 2018

 

Weather Data from the Bridge

Latitude: 29° 10.1’ N

Longitude: 093° 54.5’ W

Visibility: 10+ NM

Sky Condition: 3/8

Wind: 16 kts

Temperature:

Sea Water: 29.4° C

Air: 27° C

 

Science and Technology Log

At this point I have been able to understand more of the sonar technology taking place during the survey aboard the Thomas Jefferson. The ship uses two types of sonar: multibeam and side scan. Both work together transmitting and receiving sound pulses to and from the ocean floor. This provides a multispectral analysis.

Julia Wallace, a physical scientist, works at the sonar acquisition station. This requires a large amount of multitasking as she communicates with the bridge (ship steering deck), watches the safety cameras, and makes sure both sonar devices are working correctly.

Julia Wallace, a physical scientist, works at the sonar acquisition station. This requires a large amount of multitasking as she communicates with the bridge (ship steering deck), watches the safety cameras, and makes sure both sonar devices are working correctly.

Multibeam sonar is located underneath the hull of the ship. Multibeam is used to detect bathymetry (the depth of the ocean floor). Multibeam backscatter (reflected wave energy) gives a reading of the surface intensity. For example, a strong signal would mean a harder surface like rock or pipeline. With multibeam sonar, you can also adjust the sound wave frequency. For example, high frequency (primarily used during this survey in the Gulf of Mexico) is used for shallower waters allowing for higher resolution images. Images from multibeam have a color gradient to allow for clear vision of contours and depth differences. One way surveyors aboard the TJ may use backscatter images is to determine areas where bottom sampling might be applicable.

A NOAA ship using mulitbeam sonar. (Courtesy of NOAA)

A NOAA ship using mulitbeam sonar. (Courtesy of NOAA)

Bathymetry acquired using multibeam echosounder layered over a nautical chart.  Blue and green wave lengths penetrate further in water, so the coloring corresponds to this observation. This poster is from a previous Thomas Jefferson hydrographic survey near Savannah, Georgia. (Prepared by CHST Allison Stone)

Bathymetry acquired using multibeam echosounder layered over a nautical chart.  Blue and green wave lengths penetrate further in water, so the coloring corresponds to this observation. This poster is from a previous Thomas Jefferson hydrographic survey near Savannah, Georgia. (Prepared by CHST Allison Stone)

3D bathymetry imagery from the Okeanos Explorer. (NOAA)

3D bathymetry imagery from the Okeanos Explorer. (NOAA)

A close-up view of multibeam data. The third window down shows multibeam backscatter.

A close-up view of multibeam data. The third window down shows multibeam backscatter.

The side scan sonar is used alongside multibeam to provide black and white scans of images. Like multibeam backscatter, side scan measures the intensity of the sound returning from the sea floor. For example, a side scan return with high intensity could indicate a difference in material like pipeline or a wreck. A low intensity value could mean that the side scan sonar waves have reached a muddy substrate. Julia used the analogy of a tennis ball being bounced against a wall of different materials. For example, the tennis ball hitting a concrete wall would bounce back with higher intensity than one being bounced against a soft wall. Side scan sonar is very effective at detecting features that protrude off the sea floor, and for shallow water surveys, typically can see farther and cover a greater area the sea floor than multibeam echosounders alone.

The side scan sonar sensor is located on a torpedo-shaped “towfish” and pulled behind the boat. When viewing side scan images, surveyors typically look for the acoustic shadow cast by a feature protruding off the sea floor. By measuring the length of the acoustic shadow, hydrographers can determine whether the feature requires additional investigation. For example, the outline of a shipwreck, bicycle, or pipeline. However, it can also detect mammals like dolphins or schools of fish.

Diagram of side scan sonar. (Courtesy of thunder bay 2001, Institute for Exploration, NOAA-OER)

Diagram of side scan sonar. (Courtesy of thunder bay 2001, Institute for Exploration, NOAA-OER)

The Thomas Jefferson sidescan sonar on deck.

The Thomas Jefferson sidescan sonar on deck.

In the early morning, the sidescan sonar picked up the image of an incorrectly charted shipwreck. Height is estimated using the "shadow" of the wreck.

In the early morning, the sidescan sonar picked up the image of an incorrectly charted shipwreck. Height is estimated using the “shadow” of the wreck.

Sidescan sonar imagery layered on a nautical chart. It is important to remember that sidescan data does not account for depth, it is a measure of differences in sea floor substrate.

Sidescan sonar imagery layered on a nautical chart. It is important to remember that sidescan data does not account for depth, it is a measure of differences in sea floor substrate.

Look closely and you can see arc lines in the sidescan imagery. Lt. Anthony Klemm explains that these arcs are from ships dragging anchor and stirring up the sea floor.

Look closely and you can see arc lines in the sidescan imagery. Lt. Anthony Klemm explains that these arcs are from ships dragging anchor and stirring up the sea floor.

While this is happening, surveyors are also towing a MVP or Moving Vessel Profiler to capture information about the water column. This is important because multiple factors in the water column need to be corrected in order for accurate sonar calculations. For example, the speed of sound in salt water is roughly 1500 m/s but may change while the ship is traveling over different parts of the sea floor or passing through a thermocline (steep temperature gradient) or halocline (steep salinity gradient). The MVP is similar to the CTD used on the launch boat (see previous post), but the MVP allows the ship to continue moving at about 10 knots (average survey speed), while the CTD must be cast when the ship is stationary.

Information from the Moving Vessel Profiler. From left to right, the MVP tracks sound speed, temperature, and salinity in relation to depth.

Information from the Moving Vessel Profiler. From left to right, the MVP tracks sound speed, temperature, and salinity in relation to depth.

For more information on multispectral analysis and sonar, see these resources:

https://oceanexplorer.noaa.gov/explorations/09bermuda/background/multibeam/multibeam.html

https://oceanservice.noaa.gov/education/seafloor-mapping/how_sidescansonar.html

Personal Log

One of my goals in the classroom is to teach students to be comfortable making and learning from mistakes. Making mistakes in math and science is common and welcome because they lead to great discussion and future change. Often, my sixth graders get discouraged or so caught up in failure that they become paralyzed in making further attempts. While aboard the Thomas Jefferson, I have witnessed several aspects not go according to plan. I think these experiences are important to share because they provide real-life examples of professionals coming together, learning from mistakes, and moving forward.

Around 4:00 am, the towfish side scan sonar became entangled with the MVP. This was a horrendous disaster. The crew spent about 16 hours contemplating the issue and collecting data using the multibeam only, which is less than ideal.  One of XO LCDR McGovern’s many roles aboard the ship is to serve as the investigator. She reviewed tapes of the early morning, talked with the crew, and later held a debrief with all involved. When something like this happens, the ship must write a clear incident report to send to shore. There were many questions about why and how this happened as well how to best proceed. In the end, the towfish and MVP were untangled with no damage present to the sensor. Within the same day, both were cast out and back in use.

I find this to be an astounding example of perseverance and teamwork. Despite being disappointed and upset that a critical tool for collecting accurate data was in dire shape, the crew came up with a plan of action and executed. Part of the engineering and scientific processes include evaluation and redesign. Elements of the sea and a center drift of the side scan lead to a documented new plan and refiguring the process so that this is unlikely to happen again.

Lt. Charles Wisotzsky's sketch of the complications with launching both the sidescan sonar (which tends to centerline) and MVP towfish with a current coming from port side.

Lt. Charles Wisotzsky’s sketch of the complications with launching both the sidescan sonar (which tends to centerline) and MVP towfish with a current coming from port side.

This camera image captures the entanglement of the sidescan sonar and MVP.

This camera image captures the entanglement of the sidescan sonar and MVP.

Peaks

+Saw a tuna eat a flying fish

Flying Fish. (www.ocean.si.edu)

Flying Fish. (www.ocean.si.edu)

+There is a large sense of purpose on the ship. Despite complex sleep schedules to enable 24 hour operations with a smaller crew, people are generally happy and working hard.

+ There seems to be an unlimited supply of ice cream in the ice cream freezer. Junior Officer, ENS Garrison Grant introduced me to a new desert- vanilla ice cream, a scoop of crunchy peanut butter, and chocolate syrup. I also found the rainbow sprinkles.

Vickie Obenchain: Safety First! June 26, 2018

NOAA Teacher at Sea

Victoria Obenchain

Aboard NOAA Ship Fairweather

June 25th-July 6th, 2018

Mission: Arctic Access Hydrographic Survey

Geographic Area of Cruise: Northwest, Alaska

Date: June 26th, 2018

Weather Data from the Bridge:

  • Latitude: 58o 11.3’ N
  • Longitude: 134o 23.2’ W
  • Wind Speed: 6 knots
  • Wind Direction: East
  • Visibility: 7 nautical miles
  • Air Temperature: 12.5o C
  • Current Sky Conditions: 99% Cloud over made up of mainly stratus clouds, with a consistent drizzle

(Picture taken before consistent drizzle started.)

(Picture taken before consistent drizzle started.)

Science and Technology Log

I joined the NOAA Ship Fairweather in Juneau where it has been undergoing upgrades to its propulsion control. Due to these upgrades, yesterday and today the ship has been conducting sea trials to learn how the new upgrades work, train their crew on them and to make sure everything is calibrated accurately before we head out to sea and continue on the ship’s mission.

NOAA Ship Fairweather is a 231 foot long hydrographic (hydro meaning “water”, graphic meaning “drawing”) survey ship which helps map the sea floor and update nautical maps using sonar. A communications specialist contracting for NOAA, Gina Digiantonio, said it best (I will paraphrase her here): Would you jump into a body of water not knowing how deep it was? Or would you want to know you weren’t going to get hurt? This is the same thing ships and vessels have to plan for; will they run aground, hit rocks, is it safe enough for them to get through? By knowing the depth of the sea floor, mariners can avoid dangerous and expensive accidents to both their vessels and the environment.

This research is done not only with NOAA Ship Fairweather, but with the help of 4 smaller boats, or launches, on board. Each launch is equipped with its own sonar equipment which when all in use, help get large areas of the sea floor mapped at once.  Below you can watch one of these 8 ton launches being lowered into the Juneau harbor.

This work is incredibly important. Some nautical charts in the area date back to before the 1900’s with lesser bottom coverage and some areas in use are not mapped at all. With the forecast of complete loss of summer sea ice by 2050 in the Northwestern Alaska area, and with that the increase in commercial vessel traffic; the need for accurate maps to ensure safety of all vessels and the surrounding environment is important work.


Since I am a visitor on the NOAA Ship Fairweather; I, along with a few other visitors and new employees, took part in a safety orientation in case of emergencies. We learned where life vests and life boats are located, where to go in case of an emergency and what calls are used to notify those on the ship, as well as the procedures associated with each situation. Additionally, we had to practice getting into an immersion suit in case we had to abandon ship. These are full body wet suits which are waterproof and help prevent hypothermia.  Mine was a bit big, so I was given a smaller one. You can see me modeling a larger one here:

(Picture of me in immersion suit kindly taken by ENS Lawler)

(Picture of me in immersion suit kindly taken by ENS Lawler)

Personal Log:

I got to Juneau a day before the ship was set to start sea trials so I was able to visit Mendenhall Glacier which is about 12 miles outside of Juneau with two other visitors of NOAA Ship Fairweather.   As many glaciers are retreating around the globe, I felt lucky to go visit this one!

Mendenhall Lake inside a fairly large valley which the glacier has helped to carve over the last 3,000 years

Mendenhall Lake inside a fairly large valley which the glacier has helped to carve over the last 3,000 years

The 13 mile glacier stops at the Mendenhall Lake inside a fairly large valley which the glacier has helped to carve over the last 3,000 years.  Evidence of the glaciers movement is seen on the rocks, as they are polished from where miles of heavy ice has slid over them, over time.   This glacier has been retreating for the last 500 years and in doing so it has made new ecosystems around Juneau. These ecosystems include: a wetland for migrating birds, Mendenhall Lake which provides a wildlife habitat for native animals such as beavers and bears, not to mention a recreation area to kayak in, and a beautiful conifer rain forest I got to hike through (pictured below). The glacier’s retreat is noticeable from pictures taken over time at the visitor center.

Mendenhall Lake which provides a wildlife habitat for native animals such as beavers and bears, not to mention a recreation area to kayak in, and a beautiful conifer rain forest I got to hike through

Mendenhall Lake which provides a wildlife habitat for native animals such as beavers and bears, not to mention a recreation area to kayak in, and a beautiful conifer rain forest I got to hike through

 

Cassie Kautzer: Survey Methods! August 22, 2014

NOAA Teacher at Sea
Cassie Kautzer
Aboard NOAA Ship Rainier
August 16 – September 5, 2014

Mission: Hydrographic Survey
Geographical Area of Survey: Woody Island Channel, Kodiak, Alaska
Date: August 22, 2014

Temperature & Weather:  11.5° C  (53° F), Cloudy, Rainy

Science & Technology Log

Today was ‘Day 4’ of surveying in the Woody Island Channel next to Kodiak, Alaska.  The Woody Island Channel is a very busy waterway leading ships, boats, and vessels of all sizes into Kodiak.  The problem at the moment is that much of the Woody Island Channel has shoals (shallow areas) and rocks.  This can be very dangerous, especially since the channel has not been surveyed or mapped since the 1940’s!  At that, in the 40s, surveyors were using Lead Lines to map the ocean floor.  Lead Lines were long ropes, marked with measurements, and with a weight at the end, that were thrown out to measure the depth of the water.  Lead Lines were considered very accurate for their time.  The problem with Lead Lines is that there was no way for surveyors to map the entire ocean floor–the lead line only gave a measurement of depth in one location (point) at a time.

Drawing of Lead Line Survey, formerly used to survey water depths one point at a time.

Drawing of Lead Line Survey, formerly used to survey water depths one point at a time.

Today, NOAA Hydrographers use Multibeam Echosounders.  A Multibeam Echosounder uses sonar to send out hundreds of sound pulses and measures how long it takes for those pulses to come back.  The multibeam echosounder is attached to the hull, or bottom, of the survey launches.  To find out how deep the ocean floor is in an area, depths are generated by measuring how much time it takes for each of hundreds of sound pulses to be sent out from the echosounder, through the water to the ocean floor and back again.  The sound pulses are sent out from the echosounder in an array almost like that of a flashlight.

Image shows swath of echosounding from the hull of the launch.  Different colora represent different depths. (Courtesy of NOAA)

Image shows swath of echosounding from the hull of the launch. Different colors represent different depths. (Courtesy of NOAA)

The deeper the water, the wider the swath (band of sound pulses).  The more shoal (shallow) the water, the smaller the swath.  Basically, a wider area can be surveyed when the water is deeper.  This means that surveying near shore, near rocky areas, and near harbors can be very time consuming.  These surveys do need to be completed, however, if they are in navigationally significant areas, like the Woody Island Channel that Rainier is surveying right now.

Image of hydrographic survey methods as they've changed over time.

Image of hydrographic survey methods as they’ve changed over time.

Technological advances over the years have made it more efficient and more accurate to survey the oceans.

Using multibeam sonar, the Rainier has surveyed thousands of linear nautical miles of ocean in the past couple of years.  In 2012 the Rainier was away from its home port in Newport, Oregon for 179 days–surveying 605 square nautical miles and 9,040 liner nautical miles.  In 2013 Rainier was away from its home port for 169 days – surveying 640 square nautical miles and 7,400 linear nautical miles.  It is NOAA’s goal to get 10,000 linear nautical miles surveyed each field season between all four of its Hydro ships: Rainier, Fairweather, Thomas Jefferson, and Ferdinand R. Hassler.  Several years, the Rainier has come close to this on its own!

Personal Log

I have spent the last four days out on the survey launches, gathering data, with a bunch of amazing people.  I have had the opportunity to drive a launch several times, with skilled Coxwain and Able Seaman Jeff Mays supervising me and helping me adjust to the differences in driving/steering a heavy boat versus driving my car at home.  Jeff always took back over when we got to a rocky area or area that was shoaling up quickly.  I am grateful to him, however, for the opportunity.  As with any skill that needs to be practiced, I got a little better each time I drove.  (Trying to steer in a straight line/path on the water when dealing with wind, water currents, waves, wakes from other boats, and the boats themselves is tough! At least for me.  Coxwains Dennis Brooks and Jeff Mays make it look easy, and always kept me feeling safe aboard the launch boats!)

Me, at the wheel of a survey launch.  (Photo courtesy of HST Jackson Barry)

Me, at the wheel of a survey launch. (Photo courtesy of HSST Barry Jackson )

For My Students

Below is an update on my Alaskan Wildlife sightings.  Remember, these are all animals I have been within 20 feet of (except for the bear).  Along with the wildlife in the graph below, I have also seen hundreds of birds from a distance and several romp of otter (large groups).

Wildlife I have seen thus far, graphed using Create A Graph (nces.ed.gov/nceskids/createagraph)

Wildlife I have seen thus far, graphed using Create A Graph (nces.ed.gov/nceskids/createagraph)

Can you help me identify the pictures below?  It can be quite difficult to identify creatures and “stuff” in the dark ocean waters.

IMG_0129IMG_0138

What is it?

What is it?