Oceanographic Charts
Sanny Olafeso
Commercial and recreational boaters alike know the importance of carrying 100% up-to-date, NOAA-approved charts on board. But to be effective, nautical charts must be updated regularly. OceanGrafix uses proprietary technology to ensure that our charts contain the most up-to-date, accurate information possible.
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Seven updated volumes of USCG Light Lists provide mariners with information on lights and other aids to navigation. Each volume corresponds to a different regional area and contains more information on each aid to navigation than can be shown on charts.
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Arrive at your destination more efficiently with a copy of Distances Between United States Ports. The publication is created through the coordinated efforts of the Office of Coast Survey, National Ocean Service (NOS) and National Oceanic and Atmospheric Administration (NOAA). The calculated distances within the book are from a port of the United States to other ports in the United States and normally represent the shortest navigable routes.
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I am a Technical Lead for the Navigation Support Division of the Hydrographic Department at the Naval Oceanographic Office. I specialize in the mapping of the ocean floor using multibeam sonars and in the production of oceanographic charts. I often travel two months a year on a ship collecting oceanographic data around the world. I specialize in the mapping of seamounts.
I started out in geology because I was interested in the sediments and the rocks and features associated with sedimentology. I specialized in sedimentology because of the Mississippi River Basin where I grew up. In graduate school, I took various classes on oceanographic sediments and formations. This peaked my interest and lead me to my current profession.
My parents always encouraged me to follow my heart and that lead me to the wonderful teachers at the University of Southern Mississippi. Dr. Dean Dunn and Dr. Maurice Meylan were my biggest influences in my love of geology and oceanographic sediments and fossils.
The most fascinating aspect of my work is the travel around the world and the collection of multibeam data of the seafloor. I am extremely interested in the what the seafloor looks like that most people do not get to see.
None. I knew what I wanted to do and I wanted to stay close to home. So, I worked hard and excelled in geology, which lead me to the Naval Oceanographic Office. From there, I have worked hard to work my way up to where I am now.
A nautical chart or hydrographic chart is a graphic representation of a sea region or water body and adjacent coasts or banks. Depending on the scale of the chart, it may show depths of water (bathymetry) and heights of land (topography), natural features of the seabed, details of the coastline, navigational hazards, locations of natural and human-made aids to navigation, information on tides and currents, local dentists of the Earth's magnetic field, and human-made structures such as harbours, buildings, and bridges. Nautical charts are essential tools for marine navigation; many countries require vessels, especially commercial ships, to carry them. Nautical charting may take the form of charts printed on paper (raster navigational charts) or computerized electronic navigational charts. Recent technologies have made available paper charts which are printed "on demand" with cartographic data that has been downloaded to the commercial printing company as recently as the night before printing. With each daily download, critical data such as Local Notices to Mariners are added to the on-demand chart files so that these charts are up to date at the time of printing.
Nautical charts are based on hydrographic surveys and bathymetric surveys. As surveying is laborious and time-consuming, hydrographic data for many areas of sea may be dated and are sometimes unreliable. Depths are measured in a variety of ways. Historically the sounding line was used. In modern times, echo sounding is used for measuring the seabed in the open sea. When measuring the safe depth of water over an entire obstruction, such as a shipwreck, the minimum depth is checked by sweeping the area with a length of horizontal wire. This ensures that difficult to find projections, such as masts, do not present a danger to vessels navigating over the obstruction.
Nautical charts are issued by power of the national hydrographic offices in many countries. These charts are considered "official" in contrast to those made by commercial publishers. Many hydrographic offices provide regular, sometimes weekly, manual updates of their charts through their sales agents. Individual hydrographic offices produce national chart series and international chart series. Coordinated by the International Hydrographic Organization, the international chart series is a worldwide system of charts ("INT" chart series), which is being developed with the goal of unifying as many chart systems as possible.
The nature of a waterway depicted by a chart may change, and artificial aids to navigation may be altered at short notice. Therefore, old or uncorrected charts should never be used for navigation. Every producer of nautical charts also provides a system to inform mariners of changes that affect the chart. In the United States, chart corrections and notifications of new editions are provided by various governmental agencies by way of Notice to Mariners, Local Notice to Mariners, Summary of Corrections, and Broadcast Notice to Mariners. In the U.S., NOAA also has a printing partner who prints the "POD" (print on demand) NOAA charts, and they contain the very latest corrections and notifications at the time of printing. To give notice to mariners, radio broadcasts provide advance notice of urgent corrections.
A good way to keep track of corrections is with a Chart and Publication Correction Record Card system. Using this system, the navigator does not immediately update every chart in the portfolio when a new Notice to Mariners arrives, instead creating a card for every chart and noting the correction on this card. When the time comes to use the chart, he pulls the chart and chart's card, and makes the indicated corrections on the chart. This system ensures that every chart is properly corrected prior to use. A prudent mariner should obtain a new chart if he has not kept track of corrections and his chart is more than several months old.
Various Digital Notices to Mariners systems are available on the market such as Digitrace, Voyager, or ChartCo, to correct British Admiralty charts as well as NOAA charts. These systems provide only vessel relevant corrections via e-mail or web downloads, reducing the time needed to sort out corrections for each chart. Tracings to assist corrections are provided at the same time.
The Canadian Coast Guard produces the Notice to Mariners publication which informs mariners of important navigational safety matters affecting Canadian Waters. This electronic publication is published on a monthly basis and can be downloaded from the Notices to Mariners (NOTMAR) Web site. The information in the Notice to Mariners is formatted to simplify the correction of paper charts and navigational publications.
In 1973 the cargo ship MV Muirfield (a merchant vessel named after Muirfield, Scotland) struck an unknown object in the Indian Ocean in waters charted at a depth of greater than 5,000 metres (16,404 ft), resulting in extensive damage to her keel.[1] In 1983, HMAS Moresby, a Royal Australian Navy survey ship, surveyed the area where Muirfield was damaged, and charted in detail a previously unsuspected hazard to navigation, the Muirfield Seamount. The dramatic accidental discovery of the Muirfield Seamount is often cited as an example of limitations in the vertical geodetic datum accuracy of some offshore areas as represented on nautical charts, especially on small-scale charts.
A similar incident involving a passenger ship occurred in 1992 when the Cunard liner Queen Elizabeth 2 struck a submerged rock off Block Island in the Atlantic Ocean.[2] In November 1999, the semi-submersible, heavy-lift ship Mighty Servant 2 capsized and sank after hitting an uncharted single underwater isolated pinnacle of granite off Indonesia. Five crew members died and Mighty Servant 2 was declared a total loss.[3] More recently, in 2005 the submarine USS San Francisco ran into an uncharted sea mount (sea mountain) about 560 kilometres (350 statute miles) south of Guam at a speed of 35 knots (40.3 mph; 64.8 km/h), sustaining serious damage and killing one seaman. In September 2006 the jack-up barge Octopus ran aground on an uncharted sea mount within the Orkney Islands (United Kingdom) while being towed by the tug Harold. 1M worth of damage was caused to the barge and delayed work on the installation of a tidal energy generator prototype. As stated in the Mariners Handbook and subsequent accident report: "No chart is infallible. Every chart is liable to be incomplete".[4]
Historically the first projection, invented by Marinus of Tyre ca. AD 100 according to Ptolemy, was what is now called equirectangular projection (historically called plane chart, plate carre, Portuguese: carta plana quadrada). While it is very convenient for small seas like the Aegean, it is unsuitable for seas larger than Mediterranean or an open ocean, even though early explorers had to use it for want of a better.
The Mercator projection is now used on the vast majority of nautical charts. Since the Mercator projection is conformal, that is, bearings in the chart are identical to the corresponding angles in nature, courses plotted on the chart may be used directly as the course-to-steer at the helm.
The gnomonic projection is used for charts intended for plotting of great circle routes. NOAA uses the polyconic projection for some of its charts of the Great Lakes, at both large and small scales.[5]