Coast Guard, NOAA partner to update decades-old chart data
Posted by PA3 Jonathan Klingenberg, Tuesday, September 24, 2013
By Ensign Paul Milliken and Petty Officer 3rd Class Jonathan Klingenberg
The Coast Guard and National Oceanic and Atmospheric Administration are partnering in new ways to benefit mariners in safe navigation. In a mission unique to the Coast Guard fleet, the cutter SPAR, a 225-foot buoy tender whose primary mission is the maintenance of aids to navigation around Alaska, is responsible for the annual hydrographic survey and placement of aids to navigation in Bechevin Bay at the tip of the Alaska Peninsula. The shortest route between the Pacific Ocean and Bering Sea, the bay provides a task as challenging as it is important.
Lt. Gordon Hood, SPAR’s executive officer, can speak firsthand about how far the Coast Guard’s hydrographic abilities have advanced since 2006, when the cutter was first assigned survey responsibility. Hood served on SPAR as a junior officer and played a role in the project’s development.
“I remember when we went through Bechevin Bay, there were only a couple of feet of water under the keel,” said Hood. “We purchased commercially available depth sounders, put them on the small boats, and drove back and forth to collect data.”
In 2006 SPAR was the first Coast Guard cutter to cross Bechevin Bay bar in six years. Seven years later, the data is clearer and the technology more advanced.
The channel in Bechevin Bay is mostly made of volcanic ash. Due to the constant deposits the underwater channel shifts frequently, making navigation potentially dangerous.
“With this hydrographic mapping technology, specifically in Bechevin Bay, we simply survey ahead of the cutter (with one of the ship’s small boats) making sure where the shifting channel is that year,” said Lt. j.g. John Sloan, operations officer aboard the SPAR. “And then we make sure that it is deep enough in the channel for the ship to get in safely.”
The SPAR is one of only three Coast Guard cutters outfitted with hydrographic surveying equipment. It spends two to three days each spring sending small boats throughout the waterway to measure depth and track shifting shoals before inspecting, and often relocating, the buoys.
NOAA and the Coast Guard have worked together for decades on a multitude of mission including fisheries management, weather data buoys, and most recently Arctic expansion. Since 2008, NOAA and the Coast Guard have been working together on Alaskan hydrography. Most recently, NOAA has started exploring the possibility of using Coast Guard hydrographic data for updating nautical charts of Alaskan waters. In February, Coast Guard Commandant Adm. Robert Papp and NOAA head Dr. Jane Lubchenco solidified a long-standing organizational relationship with the nation’s first-ever cooperative maritime strategy.
In keeping with the Coast Guard-NOAA partnership, SPAR invited Tami Beduhn, a chief survey technician on the Ketchikan-based NOAA ship Fairweather, to assist summer survey operations in Bechevin Bay. Beduhn, a Big Rapids, Mich., native and graduate of the University of New Hampshire’s School of Earth Science, was delighted to join the complicated mission.
“NOAA feels very strongly about this partnership,” said Beduhn. “We all recognize that we have the potential for aligned missions and to work together to create a safe area to navigate.”
Beduhn’s responsibility aboard Fairweather was to gather all the survey data collected from seven attached small boats, process and integrate various data points, and produce a final package to submit to NOAA quality assurance. NOAA cartographers then make changes and updates to nautical charts used all over the world by recreational, commercial and government vessels.
“In Alaska, one of the reasons why we survey, and one of the reasons why NOAA has two survey-capable ships just in this region, is because a majority if the Alaskan charts are ancient,” said Sloan. “These are 80 years old, 100 years old, 200 years old. We are talking British Admiralty-era charts.”
This was not Beduhn’s first experience with the Coast Guard. As a graduate ocean mapping student with the University of New Hampshire, Beduhn had the opportunity to sail with the Coast Guard Cutter Healy, the nation’s newest and most advanced polar icebreaker. SPAR was Beduhn’s first experience on a Coast Guard ship as a survey expert, but she arrived more than prepared to assist a crew that had no formal hydrographic training. Beduhn implemented detailed points of data collection to ensure survey results were as accurate as possible. The ship’s fathometer was fed into the survey program to constantly measure depth, allowing the vessel to act as a tidal station and make comparisons with predicted tides. To measure sound speed through the water, the crew used two tools, a lead line and a digibar.
A lead line is a sounding consists of cotton line marked to measure depth. Sailors have used them for centuries to track water depth and currents. The digibar is a more modern and sophisticated electronic casting tool that sends a sensor to the ocean floor and measures the water column’s sound velocity. SPAR sailors are now trained to use both of these sounding devices.
To survey Bechevin Bay, The SPAR crew used the commercial Hypack hydrographic software. Hypack is an acquisition and processing program designed to display information in real time, collecting data from the cutter and small boat transducers.
The data is merged with information captured from fathometers, tide tables and the digibar to provide a final display. This display is overlaid on an existing electronic nautical chart to determine how the shoals have shifted. With this, the SPAR crew tracks annual changes to determine the best placement of the buoys.
Petty Officer 1st Class Michael Cobb, a boatswain’s mate aboard the SPAR, is responsible for processing survey data when it returns from the small boats. He inputs the sounding data collected into the Hypack software, a demanding and time-sensitive process. He scans the data to remove outlier information and applies tidal data observed from both predicted states and information from sounding instruments onboard SPAR to adjust the depths for the specific point of tide. This information creates a rough picture of scattered numbers and colors that Cobb overlays onto a chart for navigational use. The previous year’s data is needed to judge shifting shoals and improve predictions for buoy placement.
Cobb worked closely with Beduhn, and appreciated her technical expertise.
“We have very little knowledge retained aboard due to frequent personnel transfers,” said Cobb. “Tami has been invaluable in improving our hydrographic program. She can teach us specific methods of data management and best practices in analyzing and processing data.”
With the assistance of Beduhn and NOAA, Hood hopes to see SPAR’s final product on a nautical chart soon.
“The most rewarding part of this mission is that NOAA may actually be able to use this data on the chart,” said Hood. “It really validates our work here over the past eight years. The charts mariners are using were last corrected decades to a century ago. This will help to get them updated.”