Weather
Cloudy Visibility: 6 nm
Wind direction: Light
Wind speed: AIRS
Wave direction: 200
Swell height: 2-3ft.
Seawater temperature: 8.9 degrees C
Sea level pressure: 1018.0 mb
Temperature dry bulb: 12.2 degrees C
Temperature wet bulb: 12.2 degrees C
Personal Log
We are anchored in East Bight and I continue to work on lesson plans. We are scheduled to get underway today for Seward. I am excited because I can spend two days in Seward seeing glaciers and fjords. Although, the weather has changed and it is cloudy and overcast, there is an up side to the weather. Geologic features that are often obscure when the sun is shining show up when the weather is overcast and more contrast is provided. I take the opportunity to showcase another basic geologic feature that is well exposed.
A scenic view of part of the Shumagin Islands and the Haystacks formationThis is a type of drainage pattern is known as radial. The drainage originates from a central point and occurs on elevated features such as volcanoes.
Weather
Clear Visibility: 10 nm
Wind direction: 290
Wind speed: 6 knots
Seawater temperature: 10.6 degrees C
Sea level pressure: 1020.5 mb
Temperature dry bulb: 15.6 degrees C
Temperature wet bulb: 12.8 degrees C
Personal Log
We are anchored in East Bight and I continue to work on lesson plans. It is a beautiful clear day with many great photo opportunities. I take advantage of the expertise of Intern Umeko Foster, who gives me a crash course in using the sextant. I reluctantly admit to owning a sextant for many years and not using it to navigate. Umeko is an excellent teacher and for the first time I am able successfully move the sun to the correct position on the horizon! As a bonus, Umeko demonstrates the correct way to read degrees and minutes. After dinner, Able Seaman Leslie Abramson drives the liberty boat to and from the beach so crew members can enjoy a little r and r. I ask Leslie to take me on a cruise to a nearby outcrop of rocks with many geologic structures.
Geologic structures are everywhere in this outcrop. Save this picture to your desktop and enlarge it. How many faults, dikes, sills, and folds do see?
TAS Jacquelyn Hams uses a lead line to determine depth during a shoreline survey
Weather
Cloudy Visibility: 10 nm
Wind direction: Light
Wind speed: AIRS
Swell Waves direction: 350
Swell height: 0-1
Seawater temperature: 10.0 degrees C
Sea level pressure: 1018.5 mb
Temperature dry bulb: 15.0 degrees C
Temperature wet bulb: 12.2 degrees C
Science and Technology Log
Today I go out on a small boat with Jim Jacobson, Chief Survey Technician, ENS Megan McGovern, RAINIER Junior Officer, Erin Campbell, Survey Technician, and Corey Muzzy, Seaman Surveyor and Coxswain to conduct a shoreline survey in Porpoise Harbor. The objective of the shoreline survey is to verify some points which were identified by LIDAR (Airborne laser mapping) which may or may not be rocks along the shoreline. LIDAR is an emerging remote sensing technology that integrates the following three subsystems in to a single instrument mounted in a small airplane to rapidly produce accurate maps of the terrain beneath the flight path of the aircraft.
LIDAR (LIght Detection And Ranging) is similar to radar or sonar in that it transmits laser pulses to a target and records the time it takes for the pulse to return to the sensor receiver
Fixed reference systems
Global positioning satellite system (GPS).
Bathymetric chart reflecting points for investigation during shoreline survey
LIDAR utilizes a pulsed laser rangefinder mounted in the aircraft. While most LIDAR systems are designed to measure land elevations (“topographic LIDAR”), the technology can also measure water depths if designed with a light wavelength which will pass through water (“bathymetric LIDAR”). Bathymetric LIDAR accurately measures the travel time for both the laser return from the sea surface and the return from the seabed. If the speed of light is known and one corrects for angle, scattering, absorption at the water surface and other biases, the distance to the sea surface and seabed can be computed from these times. The difference between these distances is the water depth. In general, bathymetric LIDAR is less accurate and lower resolution than the multibeam sonar systems on RAINIER’s launches, but it can be much faster and safer in some areas.
This is a picture of a sonar image taken on the boat. The spike on the image represents a rock.
We have several LIDAR points to verify. RAINIER has been asked to investigate these points because they are around kelp which LIDAR cannot penetrate. The boat is equipped with vertical beam echo sounders so that the bottom depth is known. Once the boat reaches the point of investigation, the coxswain drives a star pattern around the point to make sure that all sides of the potential obstacle have been covered. Lead lines are used to confirm depths close to the shoreline.
The presence of a rock is indicated by the peak in the sonar image on the left. Depth of the recorder is 32.4 feet. We are able to survey all but three of our points until we have engine problems after crossing on the edge of a thick patch of kelp. Unfortunately, the engine will not start and we have to call for a tow. On the way back to the ship, I have yet another photo opportunity for some geology pictures. Nagai Island lies within a major fault zone of the Aleutian Islands so many of the rocks are folded and uplifted into spectacular structures. The beds pictured in the photograph below were deposited according to the Principle of Original Horizontality; therefore they should be stacked on top of each other in a horizontal position. Look at them now!
ENS Megan McGovern, RAINIER Junior Office and Leslie Abramson, Able Seaman.Imagine the stress that tilted these beds to the current position.
NOAA Teacher at Sea
Dena Deck
Onboard NOAA Ship Hi’ialakai June 26 – July 30, 2006
Mission: Ecosystem Survey Geographical Area: Central Pacific Ocean, Hawaii Date: July 12, 2006
Integrating backscatter with bathymetry, showing the seafloor in rich detail
Science and Technology Log
When soldiers from Napoleon’s army found the Rosetta Stone, it was a breakthrough discovery. Carved in ancient Egypt, it contained pieces of a message in known languages and also a language that had been dead for centuries. Without any link to other known languages, historians had been unable to decipher this language until the stone was found, which provided the necessary clues to translate it. Modern day ocean mappers are looking for their own Rosetta Stone that will allow them to link backscatter data to other ecological information.
A backscatter map, indicating substrate characteristics. Dark areas represent a harder seafloor, while lighter areas are indicative of a soft, sandy bottom.
Our ship, the NOAA ship Hi`ialakai, has a set of three sonars that, when used in conjunction, can provide accurate data about the seafloor. When emitted by a sonar, a “ping” comes back bringing two pieces of information with it: travel time and strength. The two-way travel time (the time it took from emission, bouncing off the seafloor and return back to the ship), coupled with the measured velocity of sound in the specific water location where the ship is traveling in, gives mappers a bathymetric view of the seafloor, revealing the depth of each of its points. (See “Painting the Seafloor” article.)
A second piece of data obtained from each ping is the strength of the signal. When sound hits a surface, above water or below, some of it is absorbed and the rest bounces back in what we experience as an echo. The strength of this echo depends on the hardness of the material that the sound is bouncing from. This is a very convenient fact of nature that is used when mapping to compliment the bathymetric map that provides the depth. The acoustic hardness of a substrate, or ocean bottom, affects the strength of the ping coming back to the sonar. In a real sense, the loudness of the echo changes if it is bouncing off sand or rock. Sand, being soft and full of small holes in between grains, will absorb quite a bit of sound. A more solid surface like a rock will provide a bigger echo for each ping that hits it.
A diver armed with a camera is towed from a boat, obtaining many pictures that will be used to groundtruth mapping data.
This strength of the signal coming back is called “backscatter” and provides mappers with a second view of the seafloor. While bathymetry is a measure of the depth, backscatter gives us a clue about the nature of the seafloor being mapped. Since coral reefs, with their calcium carbonate, provide a much harder surface than a sandy sea bottom, the two will appear differently in the backscatter map. Values of intensity range from low intensity, showing up as white and representing soft, sandy bottom, to high intensity, represented as dark areas for harder substrate in the backscatter gray scale map.
When the backscatter map shows up binary data – white and black – it is easy to infer on the type of substrate being mapped. The challenge is presented with all of the gray areas in the map. Does light gray represent coarse sand? Is dark gray indicative of sand over rocks, or thousands of coral polyps? Or maybe just rock covered by sand? Every shade of gray has a value that can indicate a type of substrate.
Mapping
Backscatter alone cannot give you these answers. With so many variables present in the mapping process, data needs to go through a “ground-truthing” process, or compared to visual observations of the sites. To do this, researchers collect video, photographs and perform actual dive observations of many of the sites that are mapped. These video and images need to be analyzed by a person. It’s a tedious process that cannot be automated – it requires having a person able to classify types of substrate from watching hour after hour of video data or many photographs. And all of these data needs to be “geo-rectified,” or coupled with GIS information to know exactly where each video segment and photograph was taken. Sometimes the payoff for “groundtruthing” backscatter is unexpected: wrecks or rich coral beds can be discovered.
We do not have yet a backscatter “signature” for each type of substrate, or sea bottom, yet. This would be the Rosetta Stone of mapping, a development which will allow mappers to correctly identify some of the ecological characteristics of each area mapped. For instance, mappers are working towards refining their backscatter analysis to allow them to tell apart live coral from bleached ones.
The NOAA Coral Reef Conservation Program has built a pilot data set from the French Frigate Shoals, consisting of large amounts of video footage, observations, and other data. They are in the process of compiling all of this information with their backscatter maps they have for the area, and study how they relate, trying to find meaning to each gray area in these maps.
When mapping, additional and unexpected discoveries can take place. Sometimes what we think of as featureless terrains are revealed to have rich topographies. In 2004, an ocean area off the island of Oahu in Hawai`i, thought to be featureless and plain, was discovered to have sand dunes and ridges, providing important habitat to the marine fauna. Interpretation of backscatter data has improved in quality over the years, and when combined with videos and photographs, remote characterization of sea floor habitats becomes possible.
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!
