echosounder – Page 5 – NOAA Teacher at Sea Blog

NOAA Teacher at Sea
Jacob Tanenbaum
Onboard NOAA Ship Henry Bigelow
October 5 – 16, 2009

Mission: Survey
Geographic Region: Northeast U.S.
Date: October 11, 2008

Science Log

Greetings from Canada, my son Nicky’s favorite place! We are now in Canadian waters. We have crossed the international boarder. More amazing things keep coming up in our nets. Today we had some interesting sea-stars. Take a look. The larger ones are called Sun-Stars. Do they look like the sun to you? Sea stars are scavengers. They will move around the bottom looking for whatever food is laying around. The legs of the sea star have small tentacles that push food towards the mouth in the center.

Did you know that squid can change color? Often male squid change color to attract a mate or to scare off other males who are competing with them. If there are two males near one female, they able to turn one color on the side facing the female, and then turn another color on the other side facing the male.

We had more dolphins circling the ship last night. We think our lights may be attracting certain fish or squid, then the dolphins come to eat that. They are not with us during the day at all. One of the benefits, I guess, of being on the night watch. I cannot shoot still photos due to the low light, but have wonderful video. The sounds that you hear on the video were recorded with the ship’s hydrophone. This is a special microphone that can record sounds underwater. The sounds were recorded as the dolphins swam around the ship. You can hear the sound of them swimming by as well as the sound of their sonar as they locate fish to eat. Click here to watch and listen. Thanks to survey technician Pete Gamache for recording this for us. Click here to see the video. Don’t miss it!

We drove past some seaweed called sargasum weed. It normally grows in an area towards the middle of the Atlantic called the Sargasso Sea. We are well west of the Sargasso, but this seems to have drifted our way. Sargasum Weed grows on the surface of the water. These huge mats of seaweed support an entire ecosystem of sea creatures. Many come to seek shelter in the weeds. Many more come to feed on smaller creatures hiding there.

Snuggy and Zee paid a visit to the fantail of the ship.

The fantail is an area by the stern of the vessel where the nets are deployed. The photos show the area where the work gets done. Our ship works all night long, of course, and trawls are done at night as well as during the day. Take a look at this video which explains how trawls are done.

Our ship is shadowing another NOAA ship, the Albatross. Why? The Albatross is an old ship and will be replaced by the Bigelow in the years to come. At this point, the ships are trawling in exactly the same place to see if they get similar results in their surveys. Making sure the vessels measure the same thing the same way is called calibration. Right now we are doing calibration with the Albatross.

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Now some answers to your questions:

RM – No we did not see Nantucket yet. We were too far out to sea. We may see it on the way back. Thanks for writing.

T – I love Block Island too. Thanks for the warning about rough seas. I am glad you and your mom are both enjoying the blog as much as I enjoy writing it for you. I’m used to the 12 AM shift now. I that I finally got 8 hours of sleep.

AR – There were TONS of skates in the water.

Hello to Mrs Eubank’s Class. Its great to hear from you. Great questions. Now for answers:

— Amanda, I think fish can get smaller pieces of plastic confused with tiny plankton, but our buoy is too large for that. I don’t think it will hurt fish. I think they will stay away from it.

–Tiffany, this is a tough question and a very good question. I guess over time, our buoy will stop working and will become floating trash. The truth is all science effects the environment you study. The trick is to do more good with your work than harm. Our buoy will help us understand our environment better so that all of us will do less harm in the future. Our ship also burns fuel as we study the ocean. That pollutes a little, but hopefully through our work, we do more good than harm to what we study.

Weston, It felt like the drifter weighs about 35 pounds or so.

Bryce, we use a large net to scoop along the bottom. The opening is about 4 meters wide.

Luke, we have not, nor do I expect to find new species. Our purpose is to learn more about the species that we already know about.

Bryce, we were about 140 miles from the nearest land the last time I looked.

RJ, some scientists made our drifter.

Weston, there are about 1000 drifters right now in the open sea.

I enjoyed your questions. Thanks for writing.

Mr. Moretti’s class, I’m not sure what killed the whale, but remember, all things the live also die. We cannot assume that something human beings did killed that whale. With all the pollution we create, we cannot assume, however, that we did not hurt it. We should stop polluting just to be sure we do not hurt other living things.

Many of you have are working hard to figure out our math question from the other day. Here is how it works. If we are going 8 knots for 24 hours, we multiply 8 times 24 and get 192 knots in a day. If we want to convert that to miles, we multiply again by 1.15 because each knot is 1.15 miles. We get 220.8 Congratulations to all who got this correct. It was a tough question.

Several of you have asked how long I would be on the ship. I will be here until the end of next week. I leave the ship on Friday October 17th.

LP – I enjoy the show Deadliest Catch very much. I think it is cool that scientists sometimes do that same kind of exciting work.

SD, there is no way for me to videotape under that water, but tomorrow I will show you how our sonars (we call them echosounders) work. That is one way to see under the water.

DT from SOMS dont’ worry, there is no light pollution out here. I am on the back deck of a working ship, so right where I am there are lights. I need them to do my job. I just have to go to the upper decks to get away from it or ask the bridge to shut them down for a bit.

NOAA Teacher at Sea
Jessica Schwarz
Onboard NOAA Ship Rainier
June 19 – July 1, 2006

Mission: Hydrographic Survey
Geographical Area: Alaska
Date: June 26, 2006

Rock hunters: SS Corey Muzzey and ENS Sam Greenaway after a productive morning of investigations. Corey, Sam and Jamie have been very giving of their time and are excellent at explaining data acquisition and processing!

Science and Technology Log

So I hope everyone remembers what RAINIER’s Captain, Guy Noll, told me last week before I went out on a launch: “We hit rocks so that you don’t have to.” When I first heard him say this, I kind of laughed, figuring it was somewhat of an exaggeration, he was only kidding with me. I found out this morning he actually wasn’t.

An added component to running lines and collecting sonar data is doing nearshore feature investigation. If you are involved in feature investigation, your job is to either prove or disprove whether or not a feature (rock, ledge, islet, wreck, etc.) actually exists in the position it’s been historically claimed to be. When I say “historically” I mean some of these features were last charted based on data collected in the 1940s or earlier. Therefore, NOAA needs to update the data used in developing their charts and resurvey various areas with updated technology.

For the last several years, NOAA has been augmenting its ship-based sonar surveys with airborne bathymetric LIDAR (LIght Detection and Ranging) data. LIDAR uses high powered laser pulses (invented in 1962!) transmitted from aircraft. The laser sweeps back and forth across the earth’s surface, and the reflections are detected by a receiver. Much like sonar, the distance to the ground can be inferred from the amount of time required for the light to travel from the airplane, to the earth, and back. If the position and altitude of the airplane are measured very accurately, the height and shape of features on the earth’s surface can be determined.

ENS Jamie Wasser, monitoring the Echosounder onboard RA1 during investigative surveys.

NASA and the U.S. Navy were among the first to use airborne LIDAR. Later, with the involvement of NOAA, Airborne Oceanographic LIDAR was developed for use in the marine environment. After continued progress in development and technology, Airborne Hydrographic LIDAR (AHL) was invented. AHL uses a wavelength of light which penetrates the water rather than reflecting off the surface, allowing for measurement of water depths in addition to land topography. Keep in mind that although ALH was first developed in the mid 80s it was not practical for utilization on the Alaska Peninsula until the 90s. Although an exciting new addition to NOAA’s hydrographic survey “toolbox”, LIDAR is not able to run nearly as deep as sonar. In shallow water close to shore, however, it can reduce the need for inefficient and potentially unsafe small boat operations. Both LIDAR and sonar are used to assist in determining what features are navigationally significant to those at sea and essentially what features will end up being charted.

RAINIER receives a list of questionable sea features based on information collected from LIDAR, past hydrographic data, and in some cases reports made by mariners. Based on this collection of data, they are asked by the Pacific Hydrography Branch (the folks in Seattle who compile RAINIER’s data for addition to the charts) to investigate certain features (i.e. rock, ledge, islet etc.) that cannot be resolved with certainty based on the LIDAR or other.

After finishing investigations, TAS Jessica Schwarz is getting a feel for steering a jet-propelled boat!

So, today, ENS Sam Greenaway, ENS Jamie Wasser, Seamen Surveyor (SS) Corey Muzzey, and I went out looking for rocks☺. That doesn’t sound nearly scientific enough does it? There’s a lot involved in looking for rocks actually, and it’s not nearly as easy as it might sound. For me, as someone new to hydrographic surveying, my big question was, “Okay, and then what happens when we find one?” What’s this whole, “hitting rocks so you don’t have to” idea? Do we really hit the rocks? I rode today in launch RA1 to do investigations. RA1 is unique because it is a jet propelled boat. This means it does not use a rudder and propeller, like you would expect to find on most power boats. Instead, RA1 is propelled (and steered) using water that is sucked in through a grill in the hull of the boat, accelerated by an impeller driven by a diesel engine, and expelled out a nozzle in the boat’s transom. Changing the direction of the discharge nozzle is what steers the boat. This allows RA1 to go into much shallower water. In fact it only needs 1 foot of water to stay afloat and move around. Also, don’t be fooled by me saying “jet propelled”. That might give someone the impression these boats are extremely fast. RA1 is actually quite slow, with a cruising speed of 12 kts, which I figure was good for the crew while I was at the helm.

There are different ways of investigating features and doing a disproval (determining if a feature is there or not). One is to use RA1’s single-beam sonar. This is different from multi-beam sonar (like what I’ve discussed before) because instead of sending out between 140-250 pings of sound over an area of between 120°-150° from the boat, single-beam sonar sends only one ping directly beneath the hull to the ocean floor. While single-beam sonar is running, the echosounder printer draws an outline of the sea floor features. Check out the picture of ENS Jamie Wasser with the echosounder to get an idea of what it might look like.

If you’re wondering why they aren’t using multi-beam instead, it’s because they’re in shallow water, extremely close to rocks, and it would be much too easy to knock off the multi-beam transducer attached to the hull. Multi-beam sonars cost around $300,000 so it wouldn’t be very cost effective for NOAA to lose or damage one. The single-beam sonar is imbedded in the hull and won’t be knocked off if the boat does happen to hit a rock.

Not all survey boats were running item investigations today. In fact today three survey boats were launched, two launches were running main scheme lines with multi-beam sonar (what I’ve participated in on past days) and one, the launch I was involved with today, was running investigations.

In order to do this, the launches need to get extremely close to shore and extremely close to these “hypothesized” features, often times physically nosing the boat up to them to check the positions (remember, “we hit rocks so you don’t have to”). Depending on the sea conditions, this can be a very difficult process.

Personal Log

Today was an excellent day. It was beautiful and sunny all day. We stopped the launch and had lunch in one of the little bays. On our way home, SS Corey Muzzey let me drive. The jet drive boats drive much differently than the boats with rudders and propellers. The helm didn’t feel nearly as touchy and seemed more forgiving of my exaggerated turns of the wheel ☺. We saw several humpbacks out there today…around the time whales started showing up near the boat was when I lost interest in driving.

The landscape here is so incredible. I keep trying to take digital pictures of it and am always disappointed by what little justice the pictures serve. Tonight is a crew beach party. Everyone on the ship who wants to go can get a ride to a nearby beach to spend some time on land for a change. I’m looking forward to it!

Soon we’ll be crossing the Gulf. I’ve been hearing some horror stories about this crossing, not just from the crew, but also from some of the people I met while I was in Sitka before I came onboard RAINIER. I’m actually looking forward to being on the open ocean. We’ve spent a lot of time anchored and well protected in the bay. Crossing the Gulf will be a new experience. I’m excited!

Calling All Middle Schoolers-We Need Help Answering a Few Questions!

Sonar technology wasn’t utilized for hydrographic purposes until the 1940s. Before this, how did surveyors chart the sea floor? Remember, hydrographic surveying and the development of nautical charts, dates all the way back to 1807 with Thomas Jefferson. So, how did they do it back then? Let me know what think!

Tag: echosounder

Jacob Tanenbaum, October 11, 2008

Jessica Schwarz, June 26, 2006