Developing products for “precision navigation”   1 comment

Ports of Los Angeles and Long Beach are first up

by Capt. Richard Brennan, chief, Coast Survey Development Lab

The increased size of vessels entering U. S. ports, coupled with the diminishing margins that must be navigated with reference to the seafloor, provides NOAA with the opportunity to develop new products to support precision navigation. The ports of Los Angeles and Long Beach are testing grounds for current product development, since developing products for these ports will allow us to examine the value of precision navigation products under actual at-sea conditions. The channel leading to the Port of Long Beach has an authorized depth of 76 feet, allowing drafts of 69 feet. A major concern for this port is high sea swell conditions that can be present when ultra large crude carriers enter port. These large swells can cause vessels to pitch, which results in a significant change in their draft.

As a point of reference, a 1,000-foot vessel pitching just 1 degree will experience a draft increase of over 10 feet. Due to these conditions, the captain of the port has limited vessel drafts to 65 feet. This may sound like no big deal, but it means that ultra-large crude carriers must wait outside of the sea buoy until conditions become favorable for them to enter or they must lighten their load to another vessel in order to reduce their draft. Both of these options are expensive delays, costing a lot of time and money.

ship clearance at 1 degree pitch

A pitch of 1 degree can significantly increase draft.

While the Office of Coast Survey is primarily focused on navigational charts, we are also working with other NOAA programs to bring all NOAA data to the mariner where it’s needed most: the ship’s bridge. We plan to expand partnerships with the commercial chart system industry and mobile app developers so we can deliver a data stream that is unified and intuitive, requiring little intervention from the mariner.

In order for this to work, soundings must be more closely spaced for a higher resolution. Along with that, each measurement must have an associated uncertainty value and some estimate of the geologic composition of the seafloor ‒ that our modern multibeam echo sounders can provide in great detail. Decidedly, the final inland electronic navigational chart product should include half-meter spaced contours and group soundings at a 25-meter radius, keeping the final electronic chart product size under the 5MB size limit. With this, as the navigation community begins to rely on – and demand – higher accuracy data, we will need more periodic surveys.

sounding and contour overlay

Close-up of the final overlay density of 25-meter radius sounding selection and half-meter contour interval

This project presents us with the opportunity to talk to the mariner about the possibilities that various NOAA data holds for navigation. To illustrate these possibilities, we will demonstrate how the whole is greater than the sum of its parts. A ship master has always intuitively understood the motion characteristics of their vessels, but knowing this intuitively is no longer good enough; we must know them exactly. High-resolution bathymetry is useful but, when paired with both real-time and forecast water levels, we are left with a much stronger decision support tool than either product used independently.

Chart of tidal prediction and actual observation

This chart shows the drastic fluctuation between tidal prediction and actual observation in the Port of Baltimore, February 2015.

These products should not only account for the astronomic factors (tides) affecting water levels, but also the meteorological and hydrological effects. For example, in February 2015, the Port of Baltimore saw a four-and-a-half foot, non-tidal water level variation in 19 hours due to the passage of a strong winter frontal system. In a wide, shallow embayment such as this, it is not uncommon for strong meteorological fronts to drive significant non-tidal water level fluctuations. The mariner must be able to account for these kinds of factors.

The NOAA products under development will encourage industry to lean forward into this new technology, and provide a vehicle to engage the mariner in a discussion about the possibilities of high-resolution data fusion for precision navigation. Whether it is a high-current situation, planning a passage, or laying out the approach to anchorage, the mariner will have all this data at their disposal to assist them with any navigation issues that may surface. With this data, the mariner has the information needed to make the best possible decision.

One response to “Developing products for “precision navigation”

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  1. Reblogged this on Boating Safety Tips, Tricks & Thoughts from Captnmike and commented:
    Shows the challenge NOAA and others face to provide safe navigation, more precise charts and channel markings as ships get larger and channels stay about the same size. More precision is needed on depths as well as understanding how reliable any measurement is.

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