Tag: multibeam mapping

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Karen Rasmussen, June, 27, 2011

NOAA Teacher at Sea: Karen Rasmussen
Ship: R/V Tattoosh
Geographical area of the cruise: Olympic Coast NMS
Date: June 27, 2011
Cruise to: Port Angeles Harbor
Crew: Nathan Witherly, Karen Rasmussen
Time: Start 10:30 – End 12:2

Mission
The first part of mission is to conduct Multibeam mapping and to collect ground-truthings at the LaPush/Teahwhit areas of the Olympic Coast National Marine Sanctuary. We will also service  the OCNM buoy, Cape Alava 42 (CA42). The second week of this mission is to explore the  Teahwhit Head moorings, ChaBa and sunken ships, and North and South moorings.

Weather Data
Calm seas/wind

Science and Technology Log

The Tatoosh at dock
The Tatoosh at dock

We began this morning at 8:00 a.m. Tatoosh had been dry  docked at the Port of Port Angeles to have the multibeam  fixed. This mission was to  have started last week but had  to be postponed because of a small leak in the multibeam. This morning the Tatoosh was  lowered into the water to take the measurements in order to  check the accuracy of the multibeam. Nathan drove the boat to Hollywood Beach (Port Angeles, WA) so we could help take readings. Rick and Nancy stayed onshore and used a surveyor’s tripod with an optical level. I held the surveyor’s rod and we completed a dynamic draft measurement of the Tatoosh. Rick took 3 readings from each position the Tatoosh was in over approximately two hours. Later Nancy and I entered their data into the Hypack software program. I read the data as she typed it in. We finished and found that our computer software programs are not interfacing with each other.

Here we are on the Tatoosh trying to work with the computer programs that will collect the data we need.
Here we are on the Tatoosh trying to work with the computer programs that will collect the data we need.

The HYPAK Program Inc. is Windows-based software created for the hydrographic
and dredging industries. It includes ways to complete surveys, collect data, process it, and generate final products.  It can be used on small or large vessels and is also used to collect environmental data.

HYSWEEP is a module of HYPACK and is used with multibeam and side scan sonar.  It gives on-the-spot information  about the ocean’s bottom  condition and data quality from  your multibeam devise.

HYSWEEP measures:

  • Depth – Nadir beam depth in survey units (ten units to one foot)
  • Time (Event)
  • Tide  Corrections
  • Draft Correction
  • Heave (in survey units, positive upward)
  • Roll – port side
  • Pitch – bow up
  • Heading
  • Easting/Northing (Like XY coordination, X= Easting, Y=Northing)

Personal Log
My learning curve is tremendous today and I am extremely tired. Last night I stayed at the Red Lion in Port Angeles. I was up until almost 4 a.m. Apparently, they are having teenager issues. Lots of horn blowing, yelling, and fighting all night long. I am hoping that tonight will be better.

I really enjoyed being part of the team today. Nancy, Rick, and Nathan have been wonderful with answering all of my questions.  Some of the questions I’ve been asking must seem so obvious to them, but my knowledge of underwater geography is so limited. Every aspect of this day has been interesting. I am truly amazed at what these people are doing with the limited and older materials they are using.

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Beth Carter, July 10, 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 10, 2007

Weather Data from the Bridge
Visibility:  2 nautical miles
Wind direction:  125 degrees
Wind speed:  11 knots
Sea wave height: 0-1 feet
Swell wave height: none
Seawater temperature:  11.7 degrees C
Dry bulb temp: 12.8 degrees C; Wet bulb temp:  12.2 degrees C
Sea level pressure:  1021.0 mb
Cloud cover: 8/8, fog and drizzle

The NOAA ship RAINIER, also known as S221, at anchor in Alaska.
The NOAA ship RAINIER, also known as S221, at anchor.

Science and Technology Log

Yesterday, I went out on launch #6, which utilizes a sonar system called the “C3D,” that produces interferometric sonar, which is a combination of side scan and multibeam sonar, to produce bathymetry.  Interferometric sonar is the latest technological advance in hydrographic mapping. This is the third technology I’ve been able to observe at work. The RAINIER has two launches that use single beam technology ( June 29 log), three launches that use multibeam technology (June 28 log), and Launch 6 has the side scan sonar.  There are advantages and disadvantages to each. Erin Campbell, my Tarheel buddy who is a physical scientist from the Pacific Hydrographic Branch of NOAA, took the time to explain some of the features and limitations of side scan sonar. The greatest advantage to side scan is that it produces sound waves that can cover a much wider swath of ocean floor, with very good resolution. This means that NOAA can be more fuel-efficient with its launches and cover more floor in less time.  Side scan can form accurate 3-D images of rocks, wrecks, and features of concern and interest on the ocean floor.  Hydrographers say that the side beam enables them to “paint the ocean floor.”

Erin Campbell, physical scientist, and Beth Carter, Teacher at Sea…two Tarheels at a rainy beach party near Bushtop Island, Alaska.
Erin Campbell, physical scientist, and Beth Carter, Teacher at Sea…two Tarheels at a rainy beach party near Bushtop Island, Alaska.

The greatest disadvantage to side scan sonar is that it does not actually provide depths associated with those features.  In other words, the hydrographers can look at the side scan images and locate a downed plane accurately on the ocean floor, but not know the exact depth of the plane. Another disadvantage to use of side scan in Alaska is that the extreme angles of slope of the islands and landforms cause the sound waves to create shadows on the resulting data. This means that some features in the shadows are missed.  Side beam sonar is used with great success on the eastern coast of the U.S., where the sea floor is sandy, is more uniform, and has less slope than in Alaska. Therefore, NOAA uses side scan to cover wide areas of territory, and then examines the images collected.  If the technicians see rocks or other potential hindrances to navigation, they send out the multibeam sonar launches to collect more detailed information on the depths.  If the concern is in a really shallow area, they might send out the single beam launches, which can get into shoal areas more easily with less threat of damage to the sonar equipment.

The C3D sonar transducer on the hull of the launch
The C3D sonar transducer on the hull of the launch

Side scan sonar is still evolving as a technology. NOAA provides valuable feedback and information to the makers of this technology, which enables the manufacturers to fine-tune and improve the technology. As I prepare to leave the RAINIER, I am impressed with the depth of knowledge of the Commanding Officer, the survey crew, and officers on the ship. They take very seriously their work, which is to take information gathered utilizing sonar, and to produce the most accurate bathymetric products possible.  The resulting charts and hydrographic maps are critical aids to shipping companies and fishermen, whose lives and safety and economic livelihood depend on the accuracy of the maps. I’ve also learned that NOAA hydrographers are called in to assist after hurricanes.  Erin, for example, was called upon to join a NRT (Navigational Response Team) after Hurricane Katrina.  There were many container ships and other ships waiting in the Gulf of Mexico for the hydrographers to survey the waters in order to locate hazards (debris in the water, wrecks, storm damage) in the water that were blocking the port and docks. NOAA has six such teams that assist when there are oil spills, wrecks, storms, etc.

Erin Campbell operating the C3D sonar aboard the launch.
Erin Campbell operating the C3D sonar aboard the launch.

Terms Used

Bathymetry:  the science of measuring ocean depths.  It is the underwater equivalent to altimetry, or measuring altitude of land forms.  Bathymetry is utilized to create DTM’s, or digital terrain models, or three-dimensional models of the ocean floor.

Hydrography: the study and science of ocean mapping.

Questions of the Day: 

  1. What kind of sonar would be best utilized in the search for a tugboat that sank unwitnessed, suspected to be in a deep harbor – vertical beam, multibeam, or sidescan sonar?
  2. To see an example of a chart created with interferometric sonar, take a look at this website.

Personal Log

I want to close out my last log with a few pictures, which definitely communicate the Alaska experience better than my words.  I also want to thank the entire crew of the RAINIER for its kind hospitality, for teaching me so much, and for reminding me what it feels like to not understand something.  I can empathize with my students so much better, as I have been in their shoes now for almost 3 weeks…struggling to understand technologies that were totally unfamiliar to me, feeling frustrated, feeling glimmers of hope when a few concepts dropped into place in my brain. Alaska is incredibly beautiful, incomprehensibly vast…I hope to return someday.

A humpback whale breaching… breathtaking sight!
A humpback whale breaching… breathtaking sight!
A bald eagle on the fly above Alaskan waters.
A bald eagle on the fly above Alaskan waters.
Alaska…known for its snow-topped majestic mountains.
Alaska…known for its snow-topped majestic mountains.  
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Beth Carter, July 9, 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 9, 2007

Weather Data from Bridge 
Visibility:  6 miles
Wind direction:  135 degrees
Wind speed:  9 knots
Sea wave height: 0-1 feet
Swell wave height: none
Seawater Temperature:  12.2 degrees C
Dry Bulb: 11.1 degrees C  Wet Bulb:  11.1 degrees C
Sea level pressure:  1022.1 mb
Cloud cover: 8/8, fog & drizzle
Depth: 22.6 fathoms

This is a view of strands of kelp as seen from the launch. Kelp appears as brown masses in thick beds.
This is a view of strands of kelp as seen from the launch. Kelp appears as brown masses in thick beds.

Science and Technology Log: 

Bull kelp…just amazing stuff.  Today I want to focus upon bull kelp and its role in the Alaskan coastal ecosystem, and its impact on hydrographers and fishermen. First of all…it is a fast-growing type of brown algae that can grow in strands from 40-65 feet long. It grows close into shore and anchors itself to rock surfaces by a root-like growth called a holdfast.  The scientific name is nereocystis leutkeana. Bull kelp has leaves called blades that grow outward from the main stem, but its most distinguishing feature is its long (2-3 feet) “bullwhip” stalks that have air bladders on their ends that can be 4” in diameter…rather like a stiff rope with a hollow onion on the end. Bull kelp can live for eight years, and reproduces via spores. Rocky substrates just off the coasts and islands of Alaska provide perfect places for the kelps’ holdfasts, and large kelp beds form in and around the islands of southeastern Alaska where the RAINIER is sailing.

In a closer view, bull kelp has some very stiff “bullwhip” like strands with air bladders on its ends. The air bladders are hollow, and look like onions or bulbs.
Bull kelp has some very stiff “bullwhip” strands with hollow air bladders on the end that look like onions or bulbs.

Bull kelp provides food and protective cover for all types of fish, invertebrates, birds and marine mammals.  Kelp beds are literally teeming with life.  Kelp waves and moves with the currents and tides. Sea otters are the most visible of the animals who depend on kelp.  They feed off the sea urchins and other invertebrates that live at the bases of the kelp. Sea urchins feed upon the holdfasts that anchor the kelp, so the sea otters keep the urchins in check in a healthy kelp bed. The otters can be seen bobbing in the kelp, lying on their backs enjoying snacks of sea urchins, clams, etc. Commander Guy Noll of the RAINIER says that kelp is a natural navigational aid in Alaska and Pacific coastal waters. If you are in a boat of any kind and you see kelp strands on the surface of the water, stay clear. Hydrographers are not particularly fond of kelp.  On the one hand, the presence of kelp indicates a rocky bottom, which is one of the features that chartmakers want to indicate on their maps.  But.RAINIER’s launches try to stay out of kelp beds, as the kelp can become caught on the sonar transducers, which are suspended from the hulls of the boats. Kelp can also be a “heads up” that there may be a hidden rocky feature that is a danger to navigation.  The launches are very careful around kelp.

The sound waves that hydrographers use for charting can also be distorted by kelp, as it is very dense in its coverage. Also, the whips and floating blade “bladders are hollow, so the echoes do not reach the underlying rocky ground. NOAA sometimes has to send divers down to get a least depth in kelpy areas, and diving in kelp is difficult because of entanglement issues. Fishermen give kelp beds a wide berth to avoid fouling their nets and equipment in the heavy, leafy, stalky bull kelp. However, they will sometimes try to trawl near kelp beds, as the kelp provides excellent cover for salmon and other fish as they hide from orcas and other predators.

Small leaves, or blades of bull kelp washed into shore add decorations to the black pebble beaches.
Small leaves, or blades of bull kelp washed into shore add decorations to the black pebble beaches.

Personal Log 

I became fascinated by kelp last week as I kayaked through some island passages that were thick with kelp. As you look into the water, you see dozens, hundreds of small snails on the blades of the kelp…I think they were black turban snails.  I tasted some of the kelp and found it, predictably…salty!  It was also chewy and gummy and difficult to swallow. Perhaps there are wonderful ways to prepare kelp to eat, but out of the water as a snack – not for me. From the launches, it is fun to see the sea otters’ heads pop up in and near the kelp beds. They manage to get their heads and shoulders out of the water…they must be standing on the kelp to get such a clear look at us! Several of the moms we saw had babies hitching rides on their bellies, or perhaps nursing. They are unbelievably cute and quick, and I am too slow to get good photographs of them.

Correction! 

Early in the trip, I wrote about the GPS, Global Positioning Satellites, and stated that there are 11 in geosynchronous orbits above the earth.  I looked up GPS on the NOAA website and found that there are 24 satellites, so I stand corrected!

Questions of the Day

1. What do you think would be the environmental impact of an oil spill on or near the rocky coasts of Alaska?  

2. What effects would it have on kelp beds? If you want a real life example of what could and has happened, “Google” the story of the Exxon Valdez, which created a huge oil spill in Prince William Sound, Alaska in 1989.

* Note: Commander Guy Noll explained that the RAINIER was one of the responding vessels after the Valdez oil spill. RAINIER did the hydrographic work needed by the Navy ships that did the cleanup. At that time, the world’s focus turned upon Prince William Sound, and as the RAINIER did the surveying, they discovered many chart errors. They spent a great deal of time surveying the area, and provided more accurate charts for the cruise ships and tourists that became interested in the beautiful area in and around Prince William Sound.

This sea otter mom and baby are floating near a kelp bed. This photograph is courtesy of Ensign Tim Smith, an excellent officer and photographer on the RAINIER.
Sea otter mom and baby are floating near a kelp bed. Photograph courtesy of Ensign Tim Smith.
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Beth Carter, July 4, 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 4, 2007

Weather from the Bridge
Visibility:  10 miles
Wind Direction:  080
Wind Speed:  3 knots
Sea wave height: 0-1 feet
Swell wave height: none
Seawater temp: 12.2 degrees C
Dry bulb temp: 12.2 degrees C; Wet bulb temp:  11.1 degrees C
Sea level pressure:  1012.2 mb
Cloud Cover: Partly cloudy, 5/8
Fathoms:  18.3

Survey technicians Shawn Gendron and Matt Boles are retrieving the “grab” from sampling the bottom.
Survey technicians Shawn Gendron and Matt Boles are retrieving the “grab” from sampling the bottom.

Science and Technology Log

On July 2, I went on launch #2 to observe the process of bottom sampling.  I would like to write in simpler language so that perhaps my first graders can read this and understand what we did. Our boat driver today Corey Muzzey, and the two surveyors were Matt Boles and Shawn Gendron. Their job today was to take samples of the sea floor. To do that, they use a special brass “claw” that is weighted down by a lead weight. They drop the claw down on a very long rope, and when it hits the bottom, a spring snaps the claw shut, and it grabs whatever is on the bottom. Then, they pull the rope and claw back up with a special winch and pulley, and look at what they got.

Sometimes, the claw picked up seaweed and mud.  Sometimes, the claw grabbed pebbles, coarse sand, fine sand, or gravel. A few times, it didn’t pick up anything, because the claw landed on solid rock. The boat driver had a special chart that he looked at to find the 19 places where they were supposed to drop the claw. Some of the spots were over 300 feet deep! They were taking these samples for two reasons: 1) The RAINIER is checking for new, safe places for anchoring for boats that use this area.  2) It is important to know what the sea bottom is like because different kinds of animals live on different types of bottom. Note that sound waves bounce off sand and rock and pebbles in very different ways. For example, sound waves that hit mud return to the boat softly. Sound waves that hit rock bounce back with more “force”, and the surveyors can tell the difference!

Matt is holding a mixture of mud and shells that came out of the grab.
Matt is holding a mixture of mud and shells that came out of the grab.

The RAINIER’s small boats, or launches, use the sound waves much as bats use them to locate obstacles when they fly. Dolphins also send out high-pitched sounds to “echolocate” their food or enemies or boats. The RAINIER uses sound waves to create maps of the sea floor. They do this by sending out sound waves, or sonar, from the bottoms of the launches.  Then they watch and record carefully how the sound waves bounce back.  They turn those recordings into maps of the ocean floor.  So, the bottom samples help them to label the maps and charts for fishermen and boaters.  They write labels on the charts like “RKY” for “rocky” areas, and “S” for sand, “SH” for shells, etc.

Personal Log 

Today we had some crazy weather. First it was sunny and calm, then windy, cloudy, rainy, and then calm again.  We saw several whales feeding near us. We also saw a small rocky island that had 30-40 Steller sea lions…the males were huge! They have just had their pups, but we couldn’t get close enough to them to see the pups.  It was a bit rough out today, and so when I tried to shut a door, I banged my shin on a door frame.  I bled so much my whole sock was bloody!  I was glad the boat had a great first aid kit.   

Questions

  1. When I saw the “claw” (look at the picture), I thought of two things…one is a piece of construction equipment, and one is a game that you can usually find at a video arcade or place like “Jungle Rapids” in Wilmington, N.C.  Can you imagine what I am thinking of?
  2. Why does it matter to a fisherman how deep the water is where he is fishing, or what kind of bottom there is below him?
A colony of Steller sea lions lies on jagged rocks in the Arriaga Passage.
A colony of Steller sea lions lies on jagged rocks in the Arriaga Passage.
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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.
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 

  1. 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?
  2. 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!