Helen Haskell: From Raw Data to Processed Data, June 16, 2017

NOAA Teacher at Sea

Helen Haskell

Aboard NOAA Ship Fairweather

June 5 – 26, 2017

 

Mission: Hydrographic Survey

Geographic Area of Cruise: Southeast Alaska – West Prince of Wales Island

Date: June 16, 2017

Weather Data

Wind:  3 knots from the east (272° true)

Visibility: 6 nautical miles

Barometer:  997.6 hPa

Air temperature: 9 °C

Cloud: 100% cover, 1000’

Location

54°54.4’N  132°52.3’W

Science and Technology Log

It would be easy to assume that once the small boat surveys are conducted and data from the larger sonar equipment on Fairweather is also acquired, that the hydrographers’ work is done and the data can be used to create navigational charts. As I have learned, pretty quickly, there are many parameters that affect the raw data, and many checks and balances that need to be conducted before the data can be used to create a chart. There are also a significant amount of hurdles that the crew of Fairweather deals with in order to get to their end goal of having valid, accurate data.  Some of the parameters that affect the data include tides, salinity of the water, temperature of the water, and the density of the data.

Tides:

Tides play a huge role in data accuracy.  But how do tides work and how do they influence navigational chart making? Tides on our planet are the effect on water due to forces exerted by the moon and the sun.  The mass and the distance from the Earth to these celestial bodies play significant roles in tidal forces. While the sun has a much greater mass than the moon, the moon is much closer to the Earth and it is distance that plays a more critical role.  Gravity is the major force responsible for creating tides. The gravitational pull of the moon moves the water towards the moon and creates a ‘bulge’. There is a corresponding bulge on the other side of the Earth at the same time from inertia, the counterbalance to gravity.  The moon travels in an elliptical orbit around the planet and the Earth travels in an elliptical orbit around the sun. As a result, the positions of the moon to the Earth and the Earth to the sun change and as a result, tide height changes.   The tides also work on a lunar day, the time it takes the moon to orbit the Earth, which is 24 hours and 50 minutes. So high tide is not at the same time in one area each solar day (Earth’s 24 hour day). There are three basic tidal patterns on our planet.  Here is southeast Alaska, the tides generally are what is called ‘semi-diurnal’, meaning that there are two high tides a day and two low tides a day of about the same height. Other areas of the world may have ‘mixed semi-diurnal’ tides, where there are differences in height between the two high and two low tides, or ‘diurnal’ tides, meaning there is only one high and one low tide in a lunar day.   The shape of shorelines, local wind and weather patterns and the distance of an area from the equator also affect the tide levels.  How does this affect the hydrographers’ data? If data is being collected about water depth, obviously tide levels need to be factored in.  Hydrographers factor this in when collecting the raw data, using predicted tide tables.  However, later on they receive verified tide tables from NOAA and the new tables will be applied to the data.

IMG_0211

The tide times of the day

Sound Speed Profiles:

Traveling down through the water column from the surface to the seafloor, several factors can change, sometimes significantly.  These factors include temperature, pressure and salinity.  These variables affect the accuracy of the sonar readings of the MBES (Multibeam Echo Sounders), so have to be factored in to account with the raw data analysis.  What complicates matters further is that these factors can vary from location to location, and so one set of readings of salinity, for example, is not be valid for the whole dataset.  Many fresh water streams end up in the waters off the islands of southeast Alaska.  While this introduction of freshwater has effects on the community of organisms that live there, it also has impacts on the hydrographers’ data.  To support accurate data collection the hydrographers conduct sound speed casts in each polygon they visit before they use the MBES.  The data is downloaded on to computers on the boat and factored in to the data acquisition.  The casts are also re-applied in post processing, typically on a nearest distance basis so that multiple casts in an area can be used.  In the picture below, the CTD cast is the device that measures conductivity (for salinity), temperature and depth.  It is suspended in the water for several minutes to calibrate and then lowered down through the water column to collect data. It is then retrieved and the data is downloaded in to the computers on board.

 

 

Data Density:

Hydrographers also need to make sure that they are collecting enough sonar data, something referred to as data density.  There are minimum amounts of data that need to be collected per square meter, dependent on the depth of the sea floor in any given area.  Having a minimum requirement of sonar data allows any submerged features to be identified and not missed. For example, at 0-20 meters, there need to be a minimum of five ‘pings’ per square meter.  The deeper the sea floor, the more the beam will scatter and the ‘pings’ will be further apart, so the minimum of five pings occupy a greater surface area.  Hydrographers need to make sure that the majority of their data meets the data density requirements.

Crossline Acquisition:

After much of the initial raw data has been collected, and many of the polygons ‘filled in’, the hydrographers will also conduct crossline surveys. In these surveys they will drive the small boat at an angle across the tracklines of the original polygon surveys. The goal here is basically quality control. The new crossline data will be checked against the original MBES data to make sure that consistent results are be acquired. CTD casts have to be re-done for the crossline surveys and different boats may be used so that a different MBES is used, to again, assure quality control.  At least 4% of the original data needs to be covered by these crossline surveys.

Shoreline verification:

Low tides are taken advantage of by the hydrographers. If the research is being conducted in an area where the low tide times correlate with the small boat survey times, then a vessel mounted LIDAR system will be used to acquire measurements of the shoreline.  Accurate height readings can be extracted from this data of different rocks that could prove hazardous to navigation.  Notes are made about particular hazards and photos are taken of them.  Data on man-made objects are also often acquired. Below are pictures produced by the laser technology, and the object in real life. (for more on LIDAT: http://oceanservice.noaa.gov/facts/lidar.html)

 

 

 

 

 

 

Night Processing:

Each evening once the launches (the small boats) return, the data from that day has to be ‘cleaned’. This involves a hydrographer taking an initial look at the raw data and seeing if there were any places in the data acquisition that are erroneous.  None of the data collected is deleted but places where the sonar did not register properly will become more apparent.  This process is called night processing as it happens after the survey day. After night processing, the sheet managers will take a look at remaining areas that need to be surveyed and make a plan for the following day.  By 6 a.m. the next day, the Chief Scientist will review the priorities made by the managers and let the HIC (Hydrographer In Charge) know what the plan in for their survey boat that day.

IMG_0281

Night Processing

Personal Log 

Throughout the Science and Technology log in this blog post, I keep referring to technology and computer programs.  What stands out to me more and more each day is the role that technology plays in acquiring accurate data.  It is an essential component of this project in so many ways, and is a constant challenge for all of the crew of Fairweather.  Daily on Fairweather, at mealtimes, in the post survey meetings, or on the survey boats themselves, there is discussion about the technology.  Many different programs are required to collect and verify the data and ‘hiccups’ (or headaches) with making this technology work seamlessly in this aquatic environment are a regular occurrence. I am in awe of the hydrographers’ abilities, not only in knowing how to use all the different programs, but also to problem solve significant issues that come up, seemingly on a regular basis.  Staff turnover and annual updates in software and new equipment on the ship also factor significantly in to technology being constantly in the foreground.  It often eats in to a large amount of an individual’s day as they figure out how to make programs work in less than forgiving circumstances.  Tied to all of this is the fact that there is a colossal amount of data being collected, stored and analyzed each field season.  This data needs to be ‘filed’ in ways that allow it to be found, and so the tremendous ‘filing system’ also needs to be learned and used by everyone.

 

 

Word of the day:   Fathom

Fathom is a nautical unit of measurement, and is the equivalent of 6 feet.  It is used in measuring depth.

Fact of the day:

Prince of Wales Island, west of which this research leg is being conducted is the fourth largest island in the United States. 4,000 people live on the island, that is 2,577sq mi.

What is this? 

fullsizeoutput_178

(Previous post: a zoomed in photo of ‘otter trash’ (Clam shell)

Acronym of the day:  

LIDAR: Light Detecting and Ranging

 

Cassie Kautzer: High Tide, Low Tide , August 30, 2014

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

Mission: Hydrographic Survey
Geographical Area of Survey: Terror Bay
Date: August 30, 2014

Temperature & Weather:  10 ° C (50° F), Cloudy, Windy (NNW winds, 5-10 kt)

Science & Technology Log

NOAA ship Rainier anchored in Japanese Bay.

NOAA ship Rainier anchored in Japanese Bay.

Since my last blog, we have come and gone from Japanese Bay, and moved on to Terror Bay.  As we were coming into Terror Bay through a narrow passage, we all got a dangerous reminder about how important hydrographic survey work is.

The nautical charts used to map our route into Terror Bay showed a depth of 25 Fathoms (150 feet), at a specific point we were traveling over.  The actual depth at that point, however, was only 7 Fathoms (42 feet).  That is only one third of the depth that was charted.  The Rainier’s draft is slightly over 14 feet (the depth from the waterline to the bottom of the Rainier’s hull, or bottom), so we were safe traveling over the 7 Fathom location.  Seeing this big of a DTON (Danger to Navigation) from the nautical charts to the actual depth, however, could be a cause for alarm.  How many other measurements are wrong?  Can we safely get the ship back out of Terror Bay?  With these thoughts in mind, one Launch boat was sent out today to survey and recon (explore/inspect) Terror Bay and ensure that we have a safe path out!

While a Launch Boat surveys, many other crew members have been busy installing and leveling new tide gauges in Terror Bay.  Tides are the daily rise and fall of the oceans, caused by the Sun and Moon’s gravitational pulls on Earth’s oceans.  The difference between low tide and high tide is the tidal range.  (The world’s biggest tidal range can be observed in Bay of Fundy, Canada.  At Bay of Fundy, high tide can be as much as 53 feet higher than low tide- all in a matter of six hours.  (onegeology.org)

high tide low tide

tidal range

Gauging sea level is trickier than just sticking a ruler or tape measure in the water because ocean waters don’t have one steady level.  Tides and currents constantly flow up and down, causing tides and water levels to be very important for hydrographic survey and other work at sea.  Hydrographic surveys are conducted at all different levels of tides.  This means shoal areas, rocks, shipwrecks, and other hazards are surveyed and recorded at all different levels of tides.  After hydrographers survey an area, they bring all the recorded data back to the ship for processing.  In processing, the depth around any hazards or dangers to navigation must be corrected based on the changing water levels.  In order to determine the necessary changes due to tides, tide stations are set up near survey areas.

A tide gauge and horcon station (horizontal control) is being set up in Terror Bay.  (Photo by Barry Jackson)

A tide gauge and horcon station (horizontal control) is being set up in Terror Bay. (Photo by Barry Jackson)

To set up a tide station, a team needs to go ashore near the area to be surveyed and explore- looking for good, stable, permanent places (like bedrock) to install tide gauges and a tide staff.  After an area is identified, a team is sent to install benchmarks.  Benchmarks for tides are like those that can be found at national landmarks and mountain peaks. Tidal benchmarks are multipurpose: they provide a frame of reference to ensure the tide staff and tide gauge orifice are stable (not moving relative to the land), they allow for comparison data in later years if we return to survey or work in this area again, and they provide stability data (the Earth’s surface, including under the oceans, is constantly changing).

Senior Survey Tech Barry Jackson drill into bedrock, preparing to install a benchmark.

Senior Survey Tech Barry Jackson drill into bedrock, preparing to install a benchmark.

Here is a benchmark cemented into bedrock near the shore line.

Here is a benchmark cemented into bedrock near the shore line.

Along with installing benchmarks, a tide staff must be set up.  A tide staff is large meter stick used for both leveling of benchmarks and for taking readings on water depth over an extended period of time.  After all instruments for the tide station are set up, the tide staff must be observed for several hours.  While observing, the water level must be measured with the tide staff and recorded every six minutes.  This data will then be compared with the data gathered by the tide gauge instruments, and hopefully, will match.

Cheif Survey Tech Jim Jacobson and Assistant Survey Tech Thomas Burrow install the Terror Bay tide staff during low tide.

Cheif Survey Tech Jim Jacobson and Assistant Survey Tech Thomas Burrow install the Terror Bay tide staff during low tide.

ENS Micki Ream reads measurements from the tide staff during higher tide.

ENS Micki Ream reads measurements from the tide staff during higher tide.

While benchmarks and a tide staff are being installed, often another team is working to install the tide gauge.   Tide gauge stations are instruments used to measure the change in sea level, over time.  They are powered by solar panels and include tubing and a sensor that must be secured under the water by a dive team.  The sensor, or orifice, must be placed on the seafloor, and anchored there, where it will always be underwater, even in low or negative tide.  The sensor uses air pressure, from a pump on shore, to measure the water depth.

Dive Master ENS Katrina Poremba and Diver ENS Micki Ream work to weight down the orifice tubing and anchor the sensor to the seafloor.

Dive Master ENS Katrina Poremba and Diver ENS Micki Ream work to weight down the orifice tubing and anchor the sensor to the seafloor.

Once everything is set up, a team will do a leveling run to measure the height of the benchmarks relative to the tide staff.  Meter sticks are held level at each of the benchmarks.  One person then reads a top, middle, and bottom thread measurement from each benchmark through a special vertical level on a tripod (kind of like a telescope).   Benchmarks are measured and compared from A to B, B to C, C to D, D to E, and the primary benchmark to the tide staff.  Then, these are all read again in a backwards run to double check and hopefully close the deal.

Assistant Survey Tech Eli Smith sets up for a level run while ENS Micki Ream prepares for data collection.

Assistant Survey Tech Eli Smith sets up for a level run while ENS Micki Ream prepares for data collection.

This is the level, put on the tripod, that allows Hydrographers to take vertical thread measurements from each benchmark.

This is the level, put on the tripod, that allows Hydrographers to take vertical thread measurements from each benchmark.

Survey work nearby can now begin, because hydrographers will have the appropriate tides data to make necessary corrections to the depth measurement gathered by the survey launches in the area!

Personal Log

This slideshow requires JavaScript.

For My Students

Find out more about TIDES *here*

Avery Marvin: Ebbs and Flows and Puffins! July 11, 2013

NOAA Teacher at Sea
Avery Marvin
Aboard NOAA Ship Rainier
July 8 — 25, 2013 

Mission: Hydrographic Survey
Geographical Area of Cruise: Shumagin Islands, Alaska
Date: July 11, 2013

Current Location: 54° 49.6 N, 159° 46.6 W

Weather data from bridge: 8.7°C, good visibility (6-8 miles), light and variable wind, overcast

View of Bird Island Cove from tide gauge installation point

View of Bird Island Cove from tide gauge installation point

Science and Technology Log:

Today, Rosalind and I were scientists in the field, helping the ship’s crew install tidal equipment in preparation for ocean floor survey work.  This was a complex process, so we decided to walk you through it in a step-by-step question format.

What does a navigation chart show you?

The image below shows a chart of the area that we are in right now. Our first anchor point was off the north coast of Bird Island in a cove. On the chart, you can see many tiny numbers in the water areas, which represent various depths.  These depths are measured in fathoms (1 fathom=6 feet).  This depth information helps mariners stay in safe areas that are not too shallow. The charts also show known hazards such as sub-surface rocks and ship-wrecks. This chart clearly has a lot of white space, signifying many areas were never surveyed.

Shumagin survey area

Part of our survey area. Notice the white spaces around Bird and Chernabura Islands!

But wait, why are the depth numbers “fixed” on the charts? Doesn’t the water level change with the tides?

Yes! It sounds easy to say, “the water is 10 fathoms deep at this point”. However, water is subject to the gravitational pull of the moon and sun, resulting in various water levels or tides throughout the day.  So the water will not always be “10 fathoms deep at this point.” For navigational purposes, the most hazardous water level is the lowest one, so nautical charts show the depth at the low tide water level.  Depending on the location, some places have two high tides and two low tides per day (semi-diurnal) and some places have one high tide and one low tide per day (diurnal). Here in the Shumagin Islands we are on a semi-diurnal mixed tide schedule (meaning that the two highs and two lows are not the same height).

How do you measure the tides each day?

shumagin_tide_zone

Map of the Shumagin Island-Sand Point Tide Zones. Notice how the eastern Shumagin Islands are 6 minutes ahead of Sand Point.

There are permanent tide measuring stations all over the globe that provide information on how to “correct for” and figure out your local tide conditions. For our case, there is a tide station at Sand Point on Popof Island, which is west from our survey area.  Our survey area is in two zones, one which is in the same zone as Sand Point and the other which is in a different zone. Therefore, we installed a tide gauge in the latter to verify that the tidal times and heights of this zone are accurately predicted by the Sand Point values. According to the current information, it says that in the different zone the tides should occur 6 minutes before the tides in Sand Point and to multiply the heights by 0.98.

A tide gauge is a pretty cool device that works by the laws of physics. It is installed (by divers) on the sea floor near a coast-line, in relatively deep water, so that it will always be covered with water. The tide gauge uses the water pressure above to determine the depth of the water column (density of water and gravity are the important factors in making this calculation). The tide gauge stays in place for at least 28 days (one full tidal cycle), after which there is a record of the water level throughout that time period (as we were gathering data), as well as a rough idea of the tidal cycle each month, ready for comparison to the Sand Point data.

How do you know if the tide gauge is working?

To verify that the tide gauge is working, humans (i.e.: Rosalind and I), take water level  measurements (in an area close to the tide gauge) using a giant meter stick or “staff”. In our case, we recorded the average water level height every 6 minutes for 3 consecutive hours.  This 3-hour data set can then be compared to the tide gauge data set for that same time period, and hopefully they will show similar trends.  

Geiger_IMG_1279 (25)

Mike (XO) and Avery, taking water level data using the staff (big meter stick)

Tide staff

This is the tide staff we used to gather water level data for comparison to the tide gauge.

Map of the Shumagin Island-Sand Point Tide Zones. Notice how the eastern Shumagin Islands are 6 minutes ahead of Sand Point.

Graph showing the water height measurements from the tide staff and the tide gauge. Notice how they appear to be increasing at the same rate! That’s good.

What happens if the survey terrain changes over time? Will that affect the water depth?

The ocean floor is above a liquid mantle, so it is possible for there to be terrain changes and this would affect water depth measurements. Thus, as scientists, we must make sure the location of our survey area is “geologically stable”. To do this, we installed “benchmarks”. If you’ve ever been to the highest point on a mountain in the United States, you might have already seen something like this: they are bronze disks that mark important places, used by NOAA as well as other agencies. We stamped our benchmarks with the year and our station data, letter A-E (by hand! with a hammer and letter stamps!), and installed them at roughly 200-foot intervals along the coastline in what we hope is bedrock. Once they were cemented in place, we determined each benchmark’s relative height in relation to the staff using a survey instrument called an optical level – this process is also called “leveling.” At the end of the survey season, the ship will come back and re-level them. If the area is geologically stable, the benchmarks should all be at the same relative heights to one another as they were when they were initially installed. More so, the scientists will also be very pleased because their ocean depth measurements will be reliable going forward in time.

Stamping a benchmark

Stamping a benchmark

Cemented benchmark

A benchmark firmly cemented in place.

Avery cements her first benchmark :)

Avery next to her first cemented benchmark 🙂

Rosalind measuring distance between benchmarks

Rosalind measuring the distance between benchmarks

So what next?

Now that we have completed all necessary pre-survey measurements and research, we are ready to begin surveying the coastline and ocean floor.  Happy Hydro!

Personal log

It’s a pretty cool feeling to know that you stepped foot on an island that hasn’t seen human visitors in 20+ years. It was also refreshing to get off the big boat and head to shore for some science fieldwork. I learned all about tide gauge and benchmark installation.  I had several small but important tasks:

  • stamp each bronze benchmark with year and appropriate code using hammer and metal letter stamps
  • mix up cement batter and add to drilled rock hole and under benchmark disc to secure it in place for years to come (much harder than it looks because the cement was like “oobleck” and not very cooperative)
  • measure distance between each benchmark using extra long tape measure
  • take water level data using staff (big meter stick) in water every 6 minutes
Cool anemome I found!

Cool sea anemone I found!

In between tasks, I perused the tide pools for various critters. I saw a few new anemones and got a great shot of one with my new underwater camera.  I absolutely love tide pooling and could spend most of the day doing it.  I also enjoyed observing the puffins flying in and out of their cliff-side home. They tended to leave the cliff in packs probably to do some offshore fishing for herring and capelin. Upon return, presumably with a belly full of fish, some puffins would fly in large circles near their dwelling a few times before finally landing. This bewildered me. I thought, what a waste of energy! So I researched this and found out the following:  Puffins are much better swimmers than flyers and have poor maneuverability while in the air. They sometimes are involved in mid-air collisions or crash landings into rocky slopes. Thus, they “size up” their landing a few times by circling near it before finally flying directly into their vertical burrow entrance.

Their body is mostly adapted for swimming, with short rigid wings helping them to “fly” underwater, to 30+ ft. depths! They have durable bones that endure pressure changes while diving and their body tissues store oxygen. They use anaerobic respiration for long dives. To waterproof their wings, puffins rub their bill on their oil gland several times and then smear this oil all over their feathers. How cool!

We are seeing a lot of Tufted Puffins out here in the Shumigans because it is breeding season (June-August), the time when they return from lonely open waters to rocky islands to mate and raise young. Puffins are monogamous, usually having one partner for many years. Interestingly, a female puffin only lays one egg, which is incubated for around 45 days! Both parents share incubation and feeding duties. Right on! The chick then stays in the nest for around 45 days until ready to fly. I love puffins! They are not only adorable but very well-adapted creatures.

Fun/sad factoid: Alaskan and Canadian natives made reversible parkas out of puffin skin. When it was rainy out, they wore the feathers on the outside and in cold dry weather, they wore the feathers on the inside. It took 45 puffins to make one parka!

Rosalind Echols: Ebbs and Flows, July 11, 2013

NOAA Teacher at Sea
Rosalind Echols
Aboard NOAA Ship Rainier
July 8 — 25, 2013 

Mission: Hydrographic Survey
Geographical Area of Cruise: Shumagin Islands, Alaska
Date: July 11, 2013

Current Location: 54° 49.6 N, 159° 46.6 W

Weather data from bridge: 8.7°C, good visibility (6-8 miles), light and variable wind, overcast

View of cove

View of our anchorage from the installation point in a sunny moment.

Science and Technology Log:

Today, Avery and I were scientists in the field, helping the ship’s crew install tidal equipment in preparation for ocean floor survey work.  This was a complex process, so we decided to walk you through it in a step-by-step question format.

What does a navigation chart show you?

The image below shows a chart of the area that we are in right now. Our first anchor point was off the north coast of Bird Island in a cove. On the chart, you can see many tiny numbers in the water areas, which represent various depths.  These depths are measured in fathoms (1 fathom=6 feet).  This depth information helps mariners stay in safe areas that are not too shallow. The charts also show known hazards such as sub-surface rocks and ship-wrecks. This chart clearly has a lot of white space, signifying many areas were never surveyed.

Shumagin survey area

Part of our survey area. Notice the white spaces around Bird and Chernabura Islands!

But wait, why are the depth numbers “fixed” on the charts? Doesn’t the water level change with the tides?

Yes! It sounds easy to say, “the water is 10 fathoms deep at this point”. However, water is subject to the gravitational pull of the moon and sun, resulting in various water levels or tides throughout the day.  So the water will not always be “10 fathoms deep at this point.” For navigational purposes, the most hazardous water level is the lowest one, so nautical charts show the depth at the low tide water level.  Depending on the location, some places have two high tides and two low tides per day (semi-diurnal) and some places have one high tide and one low tide per day (diurnal). Here in the Shumagin Islands we are on a semi-diurnal mixed tide schedule (meaning that the two highs and two lows are not the same height).

What are your experiences with high and low tides? What do you notice when you go to the beach? Leave me a comment!

How do you measure the tides each day?

shumagin_tide_zone

Map of the Shumagin Island-Sand Point Tide Zones. Notice how the eastern Shumagin Islands are 6 minutes ahead of Sand Point.

There are permanent tide measuring stations all over the globe that provide information on how to “correct for” and figure out your local tide conditions. For our case, there is a tide station at Sand Point on Popof Island, which is west from our survey area.  Our survey area is in two zones, one which is in the same zone as Sand Point and the other which is in a different zone. Therefore, we installed a tide gauge in the latter to verify that the tidal times and heights of this zone are accurately predicted by the Sand Point values. According to the current information, it says that in the different zone the tides should occur 6 minutes before the tides in Sand Point and to multiply the heights by 0.98.

A tide gauge is a pretty cool device that works by the laws of physics. It is installed (by divers) on the sea floor near a coast-line, in relatively deep water, so that it will always be covered with water. The tide gauge uses the water pressure above to determine the depth of the water column (density of water and gravity are the important factors in making this calculation). The tide gauge stays in place for at least 28 days (one full tidal cycle), after which there is a record of the water level throughout that time period (as we were gathering data), as well as a rough idea of the tidal cycle each month, ready for comparison to the Sand Point data.

How do you know if the tide gauge is working?

To verify that the tide gauge is working, humans (i.e.: Avery and I), take water level  measurements (in an area close to the tide gauge) using a giant meter stick or “staff”. In our case, we recorded the average water level height every 6 minutes for 3 consecutive hours.  This 3-hour data set can then be compared to the tide gauge data set for that same time period, and hopefully they will show similar trends.  

Tide staff

This is the tide staff we used to gather water level data for comparison to the tide gauge.

Map of the Shumagin Island-Sand Point Tide Zones. Notice how the eastern Shumagin Islands are 6 minutes ahead of Sand Point.

Graph showing the water height measurements from the tide staff and the tide gauge. Notice how they appear to be increasing at the same rate! That’s good.

What happens if the survey terrain changes over time? Will that affect the water depth?

The ocean floor is above a liquid mantle, so it is possible for there to be terrain changes and this would affect depth measurements. Thus, as scientists, we must make sure where our survey area is “geologically stable”. To do this, we installed “benchmarks”. If you’ve ever been to the highest point on a mountain in the United States, you might have already seen something like this: they are bronze disks that mark important places, used by NOAA as well as other agencies. We stamped our benchmarks with the year and our station data, letter A-E (by hand! with a hammer and letter stamps!), and installed them at roughly 200-foot intervals along the coastline in what we hope is bedrock. Once they were cemented in place, we determined each benchmark’s relative height in relation to the staff using a survey instrument called an optical level – this process is also called “leveling.” At the end of the survey season, the ship will come back and re-level them. If the area is geologically stable, the benchmarks should all be at the same relative heights to one another as they were when they were initially installed. More so, the scientists will also be very pleased because their depth measurements will be reliable going forward in time.

Benchmark gear

This is the benchmark-stamping set-up.

Rosalind chiseling

Rosalind chiseling away at the rock to ready it for benchmark installation.

Rosalind and Avery with cement

Rosalind and Avery cementing a benchmark in place for posterity.

Cemented benchmark

A benchmark firmly cemented in place.

Rosalind holding stick

Rosalind holding the level rod for the benchmark leveling process. It turns out that it is incredibly difficult to hold 12 feet of leveling rod level.

So what next?

Now that we have completed all necessary pre-survey measurements and research, we are ready to begin surveying the coastline and ocean floor.  Happy Hydro!

Personal log

One of my favorite parts about this particular activity was exploring the coastal wildlife along the way. A Harbor Seal spent a good portion of the day swimming near by and keeping an eye on what we were doing. Unfortunately, every time I tried to get closer for a picture he ducked under water. He was clearly very curious, though. No doubt the installation of the equipment seemed rather bizarre.

Installation point

This is a view of the installation point we used for the tide gauge. You can tell that the tide is low because of all the exposed animal and plant life at the base of the rocks.

Being on the rocky outcropping where we installed the tidal gauge and the beach nearby reminded me a great deal of my childhood. From the washed up bull kelp still clinging to a barnacle (sometimes still alive) to the hermit crabs scurrying away from my hand in tide pools to the brightly colored sea anemones untucking as the tide came in, it brought back a lot of fond memories and definitely re-inspired my childhood enthusiasm for exploring nature and learning about biology by experiencing it. It also brought back that sense of heightened physical awareness as I scrambled from barnacle-covered rock to barnacle-covered rock, trying to avoid the slippery foot placements that would inevitably lead to lengthy gashes on my hands. All is well. I returned from my beach adventure in one very intact piece, slightly rosy-cheeked despite the overcast conditions.

Sea anemone!

An open sea anemone. They also come in red, orange, pink, and purple!

Wildlife!

Sea Anemones, barnacles, and other rock-dwelling critters exposed at low tide.

Aside from that, as someone who loves food and eating, the Rainier has treated me very well so far. We have some wonderful stewards and cooks, who do a far better job feeding 50+ people than I do feeding one or two. Every meal includes several gourmet options, including stuffed peppers, chicken or tofu stir fry, braised beef, and countless other delicious things. And there is dessert at every meal. And a freezer full of ice cream. No wonder the crew on the Rainier seems so happy!

Robert Ulmer: Build Upon a Strong Foundation, June 19, 2013

NOAA Teacher At Sea

Robert Ulmer

Aboard NOAA Ship Rainier

Underway from June 15 to July 3, 2013

Current coordinates:  N 56⁰35.547’, W 134⁰36.925’

(approaching Red Bluff Bay in Chatham Strait)

Mission:  Hydrographic survey

Geographical area of cruise:  Southeast Alaska, including Chatham Strait and Behm Canal, with a Gulf of Alaska transit westward to Kodiak

Log date:  June 19, 2013

Weather conditions:  10.93⁰C, less than 0.5 km visibility in thick fog, 95.42% relative humidity, 1013.38 mb of atmospheric pressure, light variable winds (speed of less than 3 knots with a heading between 24⁰ and 35⁰)

 

Explorer’s Log:  Survey, sample, and tide parties

Scientists are explorers, wandering the wilderness of wonder and curiosity their with eyes and minds wide open to events, ideas, and explanations that no other humans may have previously experienced.  And by definition, explorers — including scientists — also are builders, as they construct novel paths of adventure along their journeys, built always upon the strong foundations of their own reliable cognitions and skill sets.

Ensign Rosemary Abbitt making a level sighting measurement

Ensign Rosemary Abbitt making a level sighting measurement

Starting from their own observations of the world around them, prior knowledge, and context, scientists inject creativity and insight to develop hypotheses about how and why things happen.  Testing those ideas involves developing a plan and then gathering relevant data (pieces of information) so that they can move down the path of whittling away explanations that aren’t empirically supported by the data and adding to the collective body of knowledge, so that they and others might better fathom the likely explanations that are behind the phenomena in question.

Rainier lowering a launch vessel

NOAA Ship Rainier lowers launch vessel RA-5 for a survey excursion.

Because progress along the scientific path of discovery and explanation ultimately depends on the data, those data must be both accurate and precise.  Often these terms are confused in regular conversation, but each word has its own definition.

Approaching the shore from the skiff

A view from the skiff of the shoreline where the benchmarks and tide gauge staff already are installed.

Accuracy is a description of the degree of closeness or proximity of measurements of a quantity to the actual value of that quantity.  A soccer player who shoots on goal several times and has most of his shots reach the inside of the net is an accurate shooter.  Likewise, a set of measurements of the density of a large volume of seawater is more accurate if the sample data all are near the actual density of that seawater; a measurement that is 0.4% higher than the actual density of the water is just as accurate as another measurement of the same water that is 0.4% below the actual density value.

HAST Curran McBride visually examining the condition of the tide staff

Before making more detailed data collections, Hydrographic Assistant Survey Technician (HAST) Curran first conducts a visual inspection of the previously-installed tide staff upon arriving at the shore.

Precision (also called reproducibility or repeatability), on the other hand, is the degree to which repeated measurements under unchanged conditions show the same results.  If every shot attempted by the soccer player strikes the left goalpost four feet above the ground, those shots aren’t necessarily accurate – assuming that the player wants to score goals – but they are very precise.  So, similarly, a set of measurements of seawater density that repeatedly is 5.3% above the actual density of the water is precise (though not particularly accurate).

HAST Curran McBride collecting data near the tide staff

HAST Curran collects data near the tide staff during the closing level run in Behm Canal.

The NOAA teams that conduct hydrographic surveys, collect seafloor samples, and gather data about tide conditions must be both accurate and precise because the culmination of their work collecting data in the field is the production of nautical charts and tide reports that will be used around the world for commerce, recreation, travel, fisheries management, environmental conservation, and countless other purposes.

Cabin of the launch vessel

Crew of the survey/sample team in the cabin of the launch vessel (and the Coxswain piloting the boat)

Hydrographic surveys of some sort have been conducted for centuries.  Ancient Egyptian hieroglyphs show men aboard boats using ropes or poles to fathom the depths of the water.  In 1807, President Thomas Jefferson signed a mandate establishing the Survey of the Coast.  Since that time, government-based agencies (now NOAA’s Office of Coast Survey) have employed various systems of surveying depths, dangers, and seabed descriptions along the 95,000 miles of navigable U.S. coastlines, which regularly change due to attrition, deposition, glaciation, tectonic shifts, and other outside forces.

Analyzing data aboard the launch

Hydrographic Senior Survey Technician Barry Jackson and Physical Scientist Kurt Brown analyze historic and new data from multi-beam sonar aboard the launch vessel.

For most of that history, data were collected through a systematic dropping of weighted lines (called “lead lines”) from boats moving back and forth across navigable channels at points along an imaginary grid, with calibration from at least two shore points to assure location of the boat.  Beyond the geometry, algebra, and other mathematics of measurement and triangulation, the work was painstakingly slow, as ropes had to be lowered, hauled, and measured at every point, and the men ashore often traveled alongside the boat by foot across difficult and dangerous terrain.  However, the charts made by those early surveys were rather accurate for most purposes.

Starboard of launch vessel RA-4

Starboard of launch vessel RA-4

The biggest problem with the early charts, though, was that no measurements were made between the grid points, and the seafloor is not always a smooth surface.  Uncharted rocks, reefs, or rises on the seabed could be disastrous if ships passed above them.

HSST Barry Jackson collecting sea floor sample

HSST Barry Jackson pulls a line hand over hand to retrieve a scooped sea floor sample from a depth of more than 45 meters in Behm Canal.

HSST Barry Jackson analyzing sea floor sample

… and then analyzes what the scoop captured: mud and gravel in this case.

Starting in the 1990s, single-beam sonar became the primary mechanism for NOAA’s surveys.  Still looking straight down, single-beam sonar on large ships and on their small “launch vessels” (for areas that couldn’t be accessed safely by larger craft) provided a much more complete mapping of the seafloor than the ropes used previously.  Sonar systems constantly (many times per second) ping while traveling back and forth across and along a channel, using the speed and angle of reflection of the emitted sound waves to locate and measure the depth of bottom features.

Handwritten notes about sea floor samples

Data about sea floor samples first are recorded by hand on a chart aboard the launch vessel before being uploaded to NOAA computers later.

Sound waves travel at different speeds through different materials, based on the temperature, density, and elasticity of each medium.  Therefore, NOAA also deploys CTD devices through columns of surveyed waterways to measure electrical conductivity (which indicates salinity because of ionization of salts dissolved in the water, thus affecting solution density), temperature (which usually is colder at greater depths, but not necessarily, especially considering runoff from glaciers, etc.), and depth (which generally has a positive-variation relationship with water pressure, meaning more pressure – and thus, greater density – as depth below the surface increases).

CTD device about to be deployed

This CTD device measures conductivity, temperature, and depth in the water. All three affect the speed of the sound waves in water, and the speed of sound is a necessary bit of data when using sonar (which tracks reflected pings of sound) to determine the distance to the sea floor.

The most modern technology employed by NOAA in its hydrographic surveys uses multi-beam sonar to give even more complete coverage of the seafloor by sending sound waves straight downward and fanned outward in both directions as the boat travels slowly forward.  Even though sonar beams sent at angles don’t reflect as much or as directly as those sent straight downward, uneven surfaces on the seabed do reflect some wave energy, thus reducing the occurrence of “holidays” (small areas not well-defined on charts, perhaps named after unpainted bits of canvas in portraits because the painter seemed to have “taken a holiday” from painting there).

Acquiring hydrographic data

FOO Mike Gonsalves and HAST Allix Slagle acquire hydrographic data with the ship’s Kongsberg EM-710 multi-beam sonar.

TAS Rob Ulmer retrieving sea floor sample in Behm Canal

Aboard the small launch vessel, everyone works. This is Teacher At Sea Rob Ulmer hauling in a sea floor sample in Behm Canal.

But that’s not all.  To help sailors make decisions about navigation and anchoring – and often giving fishermen and marine biologists useful information about ecology under the waterline – NOAA also performs systematic samples of the types of materials on the sea floor at representative points in the waterways where it conducts surveys.  Dropping heavy metallic scoop devices on lines* dozens of meters long through waters at various locations and then hauling them back aboard by winch or hand-over-hand to inspect the mud, sand, silt, gravel, rocks, shells, plants, or animals can be physically demanding labor but is necessary for the gathering of empirical data.

* A note about terminology from XO Holly Jablonski:  Aboard the ship, lines have a job.  Think of a “rope” as an unemployed line.

Additionally, Earth’s moon and sun (along with several underground factors) affect the horizontal and vertical movement of water on Earth’s surface, especially due to their gravitational pulls as Earth spins on its axis and orbits the sun and as the moon orbits Earth.  Therefore, information about tides is extremely important to understanding the geography of nautical navigation, as the points below the waterline are identified on charts relative to the mean low water mark (so sailors know the least amount of clearance they might have beneath their vessels), and points above the waterline are identified relative to the mean high water mark (including notation of whether those object sometimes are fully submerged).

Evidence of tidal changes along the shoreline of Behm Canal

Can you see the evidence of tidal changes along the shoreline of Behm Canal? Color differences form strata along the rocks, and lowest leaves of the trees give further evidence of the highest reach of the water.

Ensign Damian Manda manually levels the sighting rod

Ensign Damian Manda manually levels the sighting rod upon the “turtle” using a carpenter’s bubble-leveling device.

To gather accurate and precise data about tidal influences on local waters, NOAA sends tides-leveling shore parties and dive teams into difficult conditions – commonly climbing up, down, and across rock faces, traversing dense vegetation, and encountering local wildlife (including grizzly bears here in Alaska!) – to drill benchmarks into near-shore foundation rocks, install (and later remove) tidal gauges that measure changing water heights and pressures, and use sophisticated mathematics and mechanics to verify the levels of those devices.

Pondering the next measurement

Ensign Rosemary Abbitt and HST Brandy Geiger ponder the placement of equipment before the next level measurement.

Needless to say, this description is significantly less detailed than the impressively intricate work performed at every level by NOAA’s hydrographic scientists, and in the end, all of the collected data described in the paragraphs above – and more, like the velocity of the sonar-deploying vessel – must be analyzed, discussed, and interpreted by teams of scientists with broad and deep skills before the final nautical charts are published for use by the public.

Portable tools of the trade

A leveling rod is balanced on the highest point of a “turtle,” positioned carefully to be seen from multiple points.

As you choose where and how to proceed in your own journeys, remember that you can be more confident about your decision-making by using information that is both accurate and precise.  And keep exploring, my friends.

View from the benchmark

This is the view from the benchmark atop a rocky outcropping (under an 80-foot evergreen) along Behm Canal while righting a measurement rod with the tide gauge leveling party.

Did You Know?

NOAA Ship Rainier in Behm Canal with launch vessels underway

NOAA Ship Rainier in Behm Canal with launch vessels underway

Every ship in the NOAA fleet also is a voluntary mobile weather station, and so are many other seagoing vessels around the world.  For many years ships have been required to report their locations and identities on a regular basis to agencies like the U.S. Coast Guard and local or regional harbormasters.  Those periodic reports were (and still are) vital for local traffic control on the waters and for helping to provide quick response to emergency situations on vessels at sea.

View aft while launch is underway

The view aft through Behm Canal from the launch vessel

Eventually, someone insightful realized that having the ships also provide weather reports from their positions along with those identity-and-location reports would make a much richer and broader network of timely data for the National Weather Service, which is another branch of the National Oceanic and Atmospheric Administration.  As NWS adds the weather data from those many boats to the data gathered at land-based NWS stations and from voluntary land-based reporters of conditions, their models and forecasts become stronger.

(For more info about being a volunteer weather observer or volunteering with NOAA in some other capacity related to oceans, fisheries, or research, please visit www.volunteer.noaa.gov.)

Especially because weather conditions are the results of interactions among local phenomena, regional climate, and the global systems, building more accurate and precise forecast models depends on information from everywhere, but the result is that everyone benefits from the better forecasts, too.

Evidence of tectonic activity and rundown

Southeast Alaska is area with frequent tectonic activity, including uplift and earthquakes. Here a scar among the trees on the mountainside shows evidence of tectonic shifts, which also creates a ready path for meltwater to move downhill from the snowy mountaintop to the seawater below, taking trees and soil with it.

NOAA Ship Rainier ready for the returning skiff

NOAA Ship Rainier waits offshore, ready to receive the skiff returning with the tide/level shore party.

Jeff Lawrence, May 26, 2006

NOAA Teacher at Sea
Jeff Lawrence
Onboard NOAA Ship Rainier
May 22 – June 2, 2006

Mission: Hydrography survey
Geographical area of cruise: Alaska
Date: May 26, 2006

several of the deck crewmembers recovering RA 1 back to the RAINIER for the day.

several of the deck crewmembers recovering RA 1 back to the RAINIER for the day.

Weather Data from Bridge
Visibility: 10.0 miles
Wind direction: 70 degrees ENE
Wind Speed:  3 knots
Sea level pressure: 1016 mb
Present weather: overcast 1400’ clouds above ground
Temperature:  50 deg. wet/dry 52 deg.

Science and Technology Log 

Today the ship will raise anchor and head for Biorka Island.  First the crew will have to secure the temporary tide station equipment and make sure all the lines have been completed for the Wrangell Narrows.  While onboard I have had the chance to meet all of the crew of the RAINIER. The Chief Boatswain is Steve Foye and he has been a part of NOAA for 20 years now. He has served on many ships and is now on the RAINIER.  His duties include making sure all boat launches are conducted in a timely and safe manner.  When boats finish their day Steve and his crew are responsible for getting the boats back onboard the RAINIER for the night.  They also make sure the boats are fueled and ready for the next days work. Without Steve and the other deck hands little would get accomplished throughout the day. Steve is chief of the deck and is helped by

  • Able Bodied Seamen: Leslie Abramson, Jodie Edmond, and Jonathan Anderson
  • Ordinary Seamen: Dennis Brooks and Megan Guberski
  • General Vessel Assistant: Kelson Baird
  • Deck Utility Man: Kenneth Keys
  • Seaman Surveyors: Carl Verplank and Corey Muzzey
  • Boatswain Group Leader: Erik Davis
Steve Foye, Chief of the Deck Crew and admirer of nature!

Steve Foye, Chief of the Deck Crew and admirer of nature!

As you can tell it takes a lot of people working together to make sure the RAINIER gets boats in and out of the water, to their destinations, and ready for the next day.  The crew aboard the RAINIER are very skilled in what they do. Steve is also very interested in the local wildlife, marine mammals, and fauna of the Alaskan coastline.  He has had many years of experience in identifying the wildlife of this area. Anytime there happens to be wildlife near the ship, Steve is quick to tell me about it so that I can photograph the animals.  Chief Foye has a wealth of documents from the Alaskan Wildlife and Fisheries Department that help to identify the varying wildlife in the area. While onboard the RAINIER I have had the opportunity to view three Northern Sea Lions, two Alaskan Black Bears, numerous Sitka Black-Tailed Deer, a Dall’s Porpoise, many species of ducks and other birds, including the American Bald Eagle. I’ve only been aboard for 5 days and have taken numerous photos of local wildlife that I can share when with students when I return to Oklahoma.  Chief Foye has sat down with me to help me identify all the wildlife I’ve seen so far and pointed out some that he still expects to see on our way to Biorka Island.

Tomorrow we leave for Biorka Island and I am told that there is a good chance we will spot various species of porpoises and maybe a few whales. We should arrive at Biorka Island sometime Saturday afternoon where the crew will begin readying their plans for running lines of that area.

Personal Log 

Today I roamed through the ship talking to people aboard the RAINIER with various jobs. I learned many specifics about each of the crew and their responsibilities and also learned a little about them personally. The RAINIER has a good mix of people who seem to work well together.  All the crew’s members have treated me very well and I am enjoying my time aboard the RAINIER.

Questions of the Day 

Can you name 10 marine mammals that can found in Alaskan waters sometime throughout the year?

Can you name land mammals that can found in Alaska?

Can you name 10 bird species that live or migrate to Alaska?

Jeff Lawrence, May 25, 2006

NOAA Teacher at Sea
Jeff Lawrence
Onboard NOAA Ship Rainier
May 22 – June 2, 2006

Mission: Hydrography survey
Geographical area of cruise: Alaska
Date: May 25, 2006

Photo of ENS Nathan Eldridge logging weather data from the  RAINIER to be sent into NOAA for weather analysis of the area.

ENS Nathan Eldridge logging weather data to be sent to NOAA for analysis of the area.

Weather Data from Bridge as of 0730 Hours 
Visibility: 10.0 miles/16.1 Km
Wind direction: calm/no wind
Wind Speed:  calm
Sea level pressure: 1015 mb or 29.97 inches
Present weather: scattered cirrocumulus clouds, lots of sun
Temperature:  48 deg. wet/50 deg. dry

Science and Technology Log 

After completing breakfast I spent the rest of the morning on board the RAINIER and visited with the crew on some of their duties on the ship.  At 1000 hours I had a briefing on the bridge with Nathan Eldridge on how the RAINIER collects weather data every six hours that it then sends to NOAA so that, the data can be used by meteorologists for weather observations and predictions. Nathan has been aboard the RAINIER since Nov. of 2005, so this is his first full season at sea.  Nathan is an ensign signified by the acronym ENS.  He attended the NOAA Corp’s program for officer training before coming aboard the RAINIER.

ENS Sam Greenaway explains navigational charts.  Navigation is crucial to the ships success through the  Alaskan waterways.

ENS Sam Greenaway explains navigational charts. Navigation is crucial to the ships through the Alaskan waterways.

ENS Sam Greenaway has been aboard the RAINIER since Nov. of 2004.  Sam is the ships navigation officer and plots paths through the Alaskan waterways.  There are many things to read on a navigational chart, a good understanding of the charts allows Sam to plot a safe and direct path to the location at which the RAINIER will anchor next.  The ship will be leaving Wrangell Narrows for the Biorka Islands in the next day or so.

Personal Log 

Last evening I was invited by the XO, Julia Neander and AB Leslie Abramson to go kayaking in the Wrangell Narrows just before dusk.  The water was calm and the sun was slowly disappearing behind the snow-capped mountains.  The trip was very tranquil and serene. I enjoyed the experience immensely.  The crew aboard the RAINIER are very helpful and assist me in any way they can to make my stay as enjoyable and productive as possible. 

Questions of the Day 

What is the Beaufort scale and how is it used? What is the difference between a nautical mile and a statute mile? What is the difference in speed between miles per hour and knots per hour? What is the length of a fathom?

Kayaking excursion enjoyed after hours by some of RAINIER’S crew.  In photo are the XO, Julia Neander and AB Leslie Abramson.  Photo was taken by TAS Jeff Lawrence on the evening of May 24th in the Wrangell Narrows off the Alaskan coastline.

Kayaking excursion enjoyed after hours by some of RAINIER’S crew. In photo are the XO, Julia Neander and AB Leslie Abramson. Photo was taken by TAS Jeff Lawrence in the Wrangell Narrows