Nautical Chart Challenge

Discover Your World With NOAA

Nautical Chart Challenge For as long as anyone in his family could remember, The sinking of the Vansittart provided dramatic evidence of the value Francis Beaufort wanted to make scientific observations of an accurate nautical chart, and Francis Beaufort later became one from the deck of a ship. In 1789 at the age of fourteen, of history’s premier hydrographers. Today, NOAA’s O ce of Coast Survey he set sail as a sort of officer-in-training aboard the produces accurate nautical Vansittart, an East India Company tradesman bound for China and the Indies. A central goal of the Vansittart’s charts and many other journey was to survey the Gaspar Strait, where sister navigational aids that help ships of the East India Company had been lost on mariners navigate safely in dangerous and poorly charted shoals. and out of U.S. ports and along the U.S. coastline as The Vansittart found the shoals...by running hard far as 200 nautical miles aground, and taking on water so rapidly that the crew was from shore. How important forced to abandon ship on a tiny reef in the Java Sea. The waters were filled with pirates, so the crew threw is ocean navigation? You thirteen treasure chests overboard, hoping to return may be surprised to know later to reclaim them. But when they eventually made that even in the “space their way back aboard two British ships, Malay pirates age,” over 98% of the had burned and pillaged the Vansittart and the crew nation’s cargo is carried by managed to recover only three of the treasure chests. waterborne transportation.

~ based on Deﬁ ning the Wind: The Beaufort Scale, and How a 19th-Century Admiral Turned Science Into Poetry by Scott Huler, 2004 Here’s a chance to try your hand at coastal nav- i- What You Will Do gation using a modern nautical chart. Watch out for Discover some of the ways a nautical chart shoals! can help a mariner safely Wreck of U.S. Revenue Cutter TAHOMA which struck an uncharted pinnacle rock off Agattu Island, western Aleutians, navigate in unfamiliar coastal waters September 20, 1914. Courtesy NOAA Ship Collection

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What You Will Need fathom is equal to six feet), or meters. • Green buoys are printed in green with the Contour lines (called “depth curves”) letter “G” nearby. ❒ “Segment of NOAA Nautical Chart 11445, Bahia connect points of equal depth, typically Honda Key to Sugarloaf Key” 6, 12, 18, 30, 60 and multiples of 60 feet. • A number in quotation marks is the number It’s important to remember0 that10 depths painted on the buoy’s structure. How to Do It 350 20 shown 340on charts are average depths, so Before beginning your cruise, you need to 30 1. 330the actual depth at a given location may • Lighted buoys are indicated by a magenta know a few things about nautical charts. be less than that shown on the chart. 40disk printed over the small circle that Most charts contain A LOT of information, 320 0 marks the buoy’s position. including lights, buoys, wrecks, information 30 50 • The general rule for coastal navigation is about the sea bottom, shoreline features, 310 “red,330 right, returning.” This means that • The shape of 60unlighted buoys is normally water depth, and much more. These features 300 red markers, lights, or buoys should be shown by a letter. “C’ indicates a “can” are often very close together, so charts use 60 on the right side of aG vesselNET C when coming buoy whose top has a cylindrical shape many symbols and abbreviations. A complete MA 70 into port. There are many exceptions to list of these symbols is available in a 290booklet 300 this general rule, though, so it is essential • “N” indicates a “nun” buoy whose top is shaped known as “Chart No. 1,” which can be down- 80 to have a chart that shows the arrange- like a cone with the pointed end cut oﬀ (this loaded from www.nauticalcharts.noaa.gov/mcd/280 45 W (1 5° 99 90 ment of markers for a speciﬁ c 9part of the is called a “truncated” cone). R ) A

chartno1.htm (the ﬁ le containing the entire 90 V

coast. 9

publication is 85 Mb, but smaller ﬁ les con- E 270 A S • Lights on nautical charts are all shown by a N A

taining specifi c kinds of information are also 270 N E 260 R • In shallow water, markersU A are Coften fl at magenta symbol that looks like an excla- available). Here are a few basics: L N “signs” fastened to wood or metal stakes. mation point and a black dot indicating • The compass rose is a tool provided on all 100 Red markers are usually triangular, and the light’s position. Notes alongside these nautical charts to simplify the process250 green markers are square. These markers symbols120 describe the color of the light of measuring directions. On the sample 240 are shown on a chart by red triangles and and how it fl ashes.110 Some commonly used chart, the compass rose is near the240 upper green squares, and usually have a number abbreviations are: center of the chart. The most commonly that also is shown on the chart. • Q: A light fl120 ashing at a rate of not less used reference point for direction on nau- 150 230 210 than 60 fl ashes per minute tical charts is Earth’s geographic north • Buoys are shown on nautical 180charts by dia- • R: A red130 light. pole (“true north”). 220 mond-shaped symbols and a small open • G: A green light 140 210circle that indicates the location of the • If no color is indicated for a light, it is • Depths on nautical charts are shown as buoy. 150 understood to be a white light. many small numbers scattered over water 200 • Red buoys are printed190 in magenta and often160 areas. Depths indicated by these num- 180 170 have the letter “R” nearby. • Numbers next to the symbol for a light show bers are expressed in feet, fathoms (one the height of the light.

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• If numbers are inside quotation marks, this a. You and your friends board your boat at the will avoid them. How could you use your number is painted onto the light structure. dock in Doctors Arm Bay on Big Pine Key depth sounder to help steer clear of these (to the right of the compass rose). What dangers? • Numbers followed by the letter “M” show the kind of markers show the location of this approximate range of visibility of the light dock? 0 10 g. As you travel toward the snorkeling area, 350 20 in miles. 340 one of your friends notices the vegetation 30 330b. After casting oﬀ from the dock, you steer on the islands to the north. According to For example: southeast into Bogie Channel. What is the 40 the chart, what kind of vegetation is this? Q R 16ft “6” 9M 320 maximum depth shown on the chart for 0 50 indicates a red light, 16 ft high, ﬂ ash- the Channel? 30 h. According to the chart, the snorkeling area 310

ing at a rate of not less than 60 ﬂ ashes 330 is marked60 by buoys labeled “A,” “B,” “C,” per minute (“quick ﬂ ashing”), with the c. As you pass through Spanish Harbor, you and “D.” What is the color and shape of 300 60 number “6” painted on the structure, with notice a low bridgeGNET Cahead. The highest these buoys? MA 70 a visibility of about 9 miles point on your boat is 10 feet above the 290 300 water. Can you pass beneath the bridge? i. After snorkeling, you decide to visit Ramrod 2. Now it’s time to take the Chart Challenge! Key. One 80of your friends says that he can 280 45 W (1 We will use part of NOAA Nautical Chart d. You continue heading5° southeast99 until your 90 see open water between Hopkins Island 9 R )

A 90

11445, which includes the Florida Keys from depth sounderV shows a depth of 10 feet. and Cook Island. Would this be a good way 9

E 270 Bahia Honda Key to Sugarloaf Key. Suppose What does theA chart showS is probably on to go to Ramrod Key? N A

270 N E you are the captain of a 24-foot260 ﬁ shing boat, the bottom in this area?R U AL N C and are taking some friends around the j. After looking at the chart, you decide to go Keys. As the captain of a vessel, it is very e. Your friends are interested in snorkeling, to the southwest100 of Munson Island to en- 250 important to know how much water is under so you decide to take them to the buoyed 120 ter Newfound Harbor Channel. What light 240 your boat (underkeel clearance). This can snorkeling area to the south of Newfound could you110 use to be sure you avoid the vary depending on how much cargo240 you are Harbor Keys, which is part of NOAA’s shallow area to the southwest of Munson

carrying (or in this case, how many friends Florida Keys National Marine Sanctuary. Island?120 How tall is this light? 150 are aboard). Let’s say that your boat230 draws 2 Looking210 at the chart, you see that there feet, which is another way of saying that the are several shallow180 coral heads marked k. After130 passing Munson Island, you notice bottom (keel) of your boat is two feet below220 “Co” that are not marked with buoys. four markers that showing the location 140 the surface. So, you’ll need to subtract two 210 What is the water depth over these coral of Newfound Harbor Channel. What are 150 feet from the depths indicated on the chart 200heads? the color, shape, and numbers of these to ﬁ nd your underkeel clearance. 160 markers, and how would you use them to 190 180 170 f. Since the water over the coral heads is very stay in the Channel? shallow, you want to steer a course that

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l. As you enter Newfound Harbor, you notice three green markers and a red marker leading into a marina. What is the water depth near these markers?

m. You change your mind, and decide to visit Little Torch Key instead. You want to go to a marina that is to the east of the micro- wave tower on Little Torch Key. Can your vessel pass beneath the bridge between Little Torch and Big Pine Key?

n. Just before you pass beneath the bridge, one of your friends notices something sticking up out of the water. Does the chart show anything in this area?

o. After you pass under the bridge, you notice a large marina on the west side of Big Pine Key. Are there any obstacles between your vessel and this marina?

Want to Do More? For more about nautical charts and how to use them, see “Plot Your Course” at oceanservice. noaa.gov/education/lessons/plot_course.html.

To make your own nautical charts, go to: https:// oceanservice.noaa.gov/education/nautical_ charts/makechart.html St. Brendan striking out into the Atlantic - about 6th Century A.D. St. Brendan checking depths with his sounding pole. Courtesy NOAA.

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340 350 0 330 10 320 20 310 30 0 300 330 40 30 290 50 300 MAGNETI 280 C

60 60

270

70 260 45' W 5° R (1 A 9 270 9 V 9

)

' A 9 80

250 N E 90 N S U A A E

L IN C R 90

240 240

230

120 100

220 210 110 210 180 150 120 200 130 190 140 180 170 160 150

Segment of NOAA Nautical Chart 11445, Bahia Honda Key to Sugarloaf Key

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Don’t Peek… Until you have answered ALL of the Chart Challenge questions!

Answers to the Chart Challenge

a. A red triangle numbered “2” and a green h. The buoys are yellow “cans” that have a cylin- l. one to two feet square numbered “1” drical shape. m. You can pass beneath the west end of the b. 12 feet i. No, because the chart shows depths of less bridge because the vertical clearance is c. Yes, because the vertical clearance beneath the than one foot between these islands. 15 feet, but the clearance is only nine feet bridge is 11 feet j. The flashing red light which has the number “2” under the east end of the bridge. d. rocks (“rky”) painted on the structure, and is 16 ft tall and n. The chart shows three poles on the south side e. one to three feet visible for about three miles. of the bridge. f. You could use the depth sounder to follow the k. There are two square green markers numbered o. The chart shows submerged pilings to the west 12-foot depth contour line, which will keep “3” and “5” and two triangular red markers of Big Pine Key. you away from the coral heads. numbered “2” and “6”. You would steer your g. Mangroves vessel so that the red markers are to the right of the vessel and the green markers are to the left.

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