USACE Survey Boats Theyre There for You

By Tom Neale, 4/17/2009


Tom Neale's logs have a new name and home on BoatUS Magazine. We know Tom has a loyal and devoted readership, so we wanted to share his tips and insights with an even bigger audience! For the latest articles, click here for Onboard With Tom Neale.

Surveyor Thomas with 3-D displays up

A few years ago Mel and I were heading south and passing through the area where the New River Inlet intersects with the ICW in North Carolina.  In recent months many had reported running aground on hard sand, often with serious damage, even though they were in the “right place” in the ICW channel according to the aids to navigation.  As we passed this area a procession of boats ran aground. Some were huge sport fishing boats with tens of thousands of dollars of running gear getting chewed up in the sand. We went a more circuitous route, ignoring the aids, finding deep water. We called to the boats, but none answered. They were too busy hitting bottom.

All they had needed to do was to check (for free) the recent East Coast Alerts on the BoatUS website. These had detailed the recent survey findings for this area by the U.S. Army Corps of Engineers (USACE). Accurate charts, dredging information, some of the information included in USCG Notices to Mariners and many more invaluable benefits for boaters come from the USACE. In most areas, the bottom continuously changes. Except where there are stable rock bottoms, sand bars shift, mud banks build, shoals move. But what most of us don’t realize is that we have an amazing arsenal of information from the USACE to help us.

The "Florida"

On March 28, 2009 Mel and I visited the 65-foot USACE survey boat, “Florida” as she was at the dock at Camachee Cove Yacht Harbor in St. Augustine, waiting for canvas work over her aft deck. Obviously unable to conduct surveying while this work was being done, the men aboard were busy sanding and painting the vessel. Surveyor Tommy Thomas gave us a fascinating explanation of how they keep up with the constantly changing bottom of our waterways.

As the Captain runs the boat, the surveyor operates a complex array of survey equipment while they’re surveying. He sits in the main cabin surrounded by three large monitors. Nearby is a large Dell mainframe and a very large printer capable of creating charts and large scale reproductions of survey data. Below, beneath the hull, is a multi-beam transducer which looks not just directly down, as does your depth finder, but also around and off to the sides. It can usually “see” out and paint the bottom from 40 to 130 feet out depending upon silt and other material in the water, turbulence, proximity of the bank and other factors. There is also, of course, a basic straight down view do see what’s directly under the vessel.

Up above the cabin are at least two GPS antennas which lock on to multiple satellites, from different “positions” on earth (even though the positions are very close because they’re on the same boat) in order to establish exactly where the boat is and its precise orientation. There’s also a device which constantly measures instant by instant degree of roll, heel or pitch. In addition, there are often survey monuments on the nearby shores upon which the survey team will typically have placed transmitters to get a triangulation between the satellite information and known location of the monument. This further precisely positions the boat’s location and orientation and, also very importantly, the precise status of level of water (the tide) in which the boat is floating.  There is also a sound velocity probe which is periodically hung over the side. This device measures the speed of sound through the water. Speed of sound transmission will vary with factors such as turbidity, temperature, silt and many other factors.  This information allows for more precise interpretation of the beams emanating from the transducer on the bottom.

Layers of Bottom Contour Colors indicate depths

All of this data and more is fed into the computer, digested and put into useable form by a very high level survey program by Hypack, Inc ( ).

Results are displayed on the monitors, in formats chosen by the program and/or the surveyor.  To run a survey in an area, the surveyor with the program establishes lines of course on his computer, calculated to secure complete coverage of the area being surveyed. These are transmitted to a monitor in the wheel house. The captain follows those lines precisely. The computer tells him of the slightest deviation. This is a very difficult job with winds, waves, eddies, cross currents, other traffic and other factors, but the Captain works diligently to keep the boat on the “line.” The surveyor, aft in the main cabin, accumulates the data and it is displayed on his screens.  The bottom depths are indicated in multiple display modes, including color. For example, chartreuse would indicate more depth than yellow which would indicate relatively shallow water. The computer assimilates and interprets all the data and gives a very accurate picture of the bottom or, as I would say, “where the water is.”

You can see ridges The bottom underneath us

Some smaller survey boats only have “straight down” looking single beam transducers, and they must work back and forth across a channel. This larger vessel is far more complex. Mr. Thomas said that he’d been a land surveyor for around 30 years, and had been doing this type of survey work for approximately 5 years. He said the issues and complexity of bottom surveying are truly amazing, and also fascinating. We found it fascinating too, not just because of all the equipment and its capabilities, but also because it shows a dimension of information of which few boaters are aware.

Tom’s Tips on Survey Boats

1. When you sea a USACE survey boat, be sure to slow down, give it a wide berth and don’t give it a wake. If they are surveying, this makes their job more difficult.

Click Here for More Tips

With this information the agency can provide information as to what areas need dredging, can provide the information that the huge dredge operations need as to where to dredge, can accurately investigate reports of shoaling or obstructions, can give information to the Coast Guard to warn boaters of new shoals and to reposition aids to navigation, and can do much more. All this benefits the boater. You can get the information from their websites. If you don’t have time to do all that researching, you can get summaries of relevant portions of it, with web site references, on East Coast Alerts, a service provided by the BoatUS web site free to the public. A direct link is: You can also find it by following links from the home to page to these Cruising Logs or by going to Forums. The East Coast Alerts give much other information in addition to that obtained from the surveys. Other information includes bridge closings, pertinent Local Notice to Mariners, danger areas, notices of public comment opportunities, and much more. If you don’t have time to check the site regularly, you can sign up for free emails of these updates. Just click on the link above, then click on the sign-up link at the top of the page, and they come your way from BoatUS when posted.

The USACE, with hard work by good people, intelligent use of resources and extremely sophisticated equipment can help to make your boating better and safer. Take advantage of it.