I began this topic to address an easy way to convert between magnetic and chart bearings, but the topic seems to have metastasized into a discussion of making charts and route plotting. So be it. One is an integral part of the other. Three techniques for plotting charts are described. These techniques are not new. They have been described elsewhere and presented in several books on kayak navigation. I have just gathered them here for easy reference. These are all very basic topics and do not address some of the complexities one runs into in the real-world. These may come later.
Also included are links to some sites where you can purchase supplies and charting tools. Finally, coming full circle, I'll show you an easy way to account for declination that does not require memorizing a mnemonic. It just requires re-adjusting your thinking. We'll do a couple of examples to show how to convert chart bearings to compass bearings and back again.
Let's get started.
Creating Your Own Charts
How you go about preparing your charts ultimately comes down to where you will be doing your work and the types of tools in your toolbox. Obviously, if you are in a kayak camp, preparing for the next day's adventure, it is unlikely that you will have a laptop and printer available. But, if you do most of your work in advance, from your home computer, here is what you will need.
Starting from scratch, you will need a chart for the area you plan on paddling. This may be a commercially prepared chart or a home-printed chart. Commercial charts are available through most marine suppliers. A good source, with a wide selection of charts, is West Marine. Most of these are larger charts however and can be cumbersome to use on the deck of a bouncing kayak. For this reason I suggest that you print and laminate your own smaller, notebook sized charts. To do this you will need: a computer with internet access, a color printer, sheets for laminating the final chart, and probably, a thermal laminator. Lamination can be done using press-on sheets, but results are variable in my experience. Given the low cost of high quality thermal laminators and the clarity of thermal sheets (2), I highly recommend investing in one. Thermally laminated charts are reusable, can be marked up and erased repeatedly, and will quickly become the seeds for a much larger personal chart library.
You will also need a complete set of charting tools: parallel rulers, a ruler or straight edge, a china marker, a fine or extra-fine rolling ball pen, and a high quality hiking compass. Parallel rulers may be purchased from a marine supplier. Hiking compasses are available from a number of outdoor outfitters. A number of websites offer instructions on compass use. The other items are stock at most office supply stores.
I'll talk about printing and laminating charts as the need arises in the following sections.
Preparing routes using prepared charts, parallel rulers, and the compass rose (Figure 1)
This is the easiest and most straightforward technique for charting routes. You will need a waterproof nautical chart with a compass rose, a china marker, and parallel rulers.
First, using an erasable china marker, trace out your route by marking waypoints and connecting them with straight-line segments. Place an arrowhead symbol at the end of each segment to denote direction of travel. Referring to Figure 1, lay one edge of the parallel ruler along a segment of the route, in this instance the segment from A to B, and open the rulers until the parallel ruler intersects the "+" at the center of the compass rose. From the outer ring of the compass rose, read chart bearing for the leg. In the illustration, the chart bearing is 62°. Normally, this is not useful information. What you seek for your chart is the magnetic bearing. Read 46° (rounded) from the inner ring of the rose. Write the bearing along the side of the line segment and mark it with "M" to indicate it is a magnetic bearing.
In the chart used for this example, declination is 16° 30' East. This is the number of degrees and direction from True north that a compass needle points at any location in the chart area. Declination varies from chart to chart. Sometimes local variations also occur within a charted region. These can generally be ignored.
To obtain compass bearings for the remaining legs of the route, reposition the parallel rulers on another line segment and repeat.
Rose Point Navigation Systems offers a downloadable, trial version of their chart-generating software called Coastal Explorer Express (3). It comes in two flavors: Coastal Explorer Express Viewer and a version that integrates real-time positioning data from your GPS. Both systems utilize NOAA charts. These are trial versions that automatically download and install NOAA charts during the setup process. If you find the software useful and plan to continue using it, you may also find the purchase price reasonable. The trial version does not uninstall after the expiration date, however, charts will not continue to be updated and some real-time features included with the software will no longer function properly, e.g, buoy wind and temperature information and wind and current speeds. For most of us, the elements that remain continue to be useful long after expiration.
NOAA BookletCharts (1) are full-scale nautical charts that have been divided into pages and put into a printable PDF format for convenience. NOAA supplies these online at no charge. You may view and/or download them from the NOAA website.
Each BookletChart contains between 9 and 28 notebook sized pages that print on 8-1/2" x11" paper. Charts are available for the Atlantic, Gulf, and Pacific Coastal regions, as well as for Alaska and the Great Lakes. Chart size varies from 1,200,000 scale (good for surveying large areas of coastline) to 10,000 scale (good for harbor detail). For kayak use, the 40,000 and 80,000 scales are ideal. Page 1 of each BookletChart contains the chart index. The charts are identified by page number and illustrate the approximate chart areas detailed. Page 2 contains selected excerpts from Coast Pilot. While not so useful on water, the information on this page can help familiarize you with select areas on each chart; such as the location of harbors, shoals, obstructions, buoys, and VHF-FM radio channels monitored. Emergency information and instructions on how to place a distress call are printed on the last page of each BookletChart.
Each system for chart making has its own set of peculiarities. Coastal Explorer Express allows you to chart your anticipated route using your desktop or laptop computer, then print it directly. The software automatically corrects for declination and marks each segment of your route vector containing a magnetic bearing and a distance (see Figure 2 for an example printout). Unfortunately, you cannot select the printed area. Sometimes you may have to print several pages before the right framing is achieved. Also, the printed chart probably will not contain information that is key for navigation. For example, you probably will not see a compass rose, a declination factor, or a distance scale on your printed chart. BookletCharts share some of these same issues. While BookletCharts always print what you see on the computer screen, all pages in the booklet do not contain a compass rose or a distance marker. Labeled lines of latitude and longitude are missing from all but the charts that lie on the outer edges of the larger chart.
Coastal Explorer Express provides you with tools for marking and labeling your route (see Figure 2), whereas this must to be done manually on charts printed from BookletCharts. Lets take a look at how that is done.
This method utilizes libraried charts, i.e., charts you have made for previous paddles in the same area and saved in your own personal library. If your library does not contain a suitable chart, print one using the tools described previously. Manual chart preparation has the added advantage of not requiring a computer. Advantage you say? Yes, advantage. Libraried charts can be revised at almost any time; at home, in camp, or on the deck of your kayak. If you decide to add a side-trip while en route, you may do so quickly and easily. Hence, this is a very good technique to know.
You will need a china marker, a hiking compass, and a ruler (you can use the side of your compass).
Before proceeding, I need to clarify some terms. Depending upon whom you read, the deviation from true north on any chart may be referred to as either "variation" or "declination". Sometimes these terms are used interchangeably. In my vocabulary they imply different things and I believe that once you begin calling magnetic deviation by it's correct term, declination, and not variation, you will no longer have difficulty converting between compass bearings and chart bearings. The distinction is more than semantic. The term declination stems from "decline," meaning to become smaller or reduce. It imparts direction to the manner in which the value is applied. Variation, on the other hand, is defined as "…a change or slight difference in condition, amount, or level, typically with certain limits." While this does apply to cartography generally, it is not suitable for use in describing deviation on a specific chart where the variable has a finite value.
To better understand why this distinction is important, consider this. Declination refers to the amount that must be subtracted from True North to correct your magnetic compass. That's pretty simple. No pneumonic is necessary to determine if it must be added or subtracted. It is, quite simply, always subtracted. Before you slam me for this irreverence to convention continue reading.
Declination is the offset that must be subtracted from True north to correct for the physical separation of the geographical and magnetic poles. If you are planning a paddle in waters east of the Mississippi, then declination will take on a negative value. If you are planning to paddle waters west of the Mississippi, declination will have a positive value. The algebraic expression relating magnetic bearings to chart bearings on both sides of the Mississippi, is:
Magnetic bearing = Chart bearing - declination. (1)
The catch to using a single equation for all of your corrections lies in remembering to sign declination. East declination is always positively signed and West declination is always negatively signed. (It's should be obvious, but just for clarity, East and West, used in this context, refer to which side of True North the declination arrow resides. East and West do not refer to the continental areas divided by the Mississippi river.)
Let's do a few real world examples.
Converting chart bearings to magnetic, or compass, bearings (Figure 3)
You are kayaking with your buddies. Your destination is a small island a few miles off Maryland's Eastern shore (See Figure 2). The route shows you will have to navigate through a series of small islands. Looking at your charts, you note that the distances between several of the islands are greater than 2 miles. Suddenly, a bulb lights in your mind with a caption stating, "From our viewpoint we won't be able to see the our next destination at multiple points along this route. We will have to navigate by dead-reckoning!" This is followed by a slurry of curse words targeting your friend whom you trusted to make the trip maps, and yourself for giving him the responsibility then not checking the charts yourself. Your charts have no compass bearings!
You pull along the shoreline of the first island on your route and begin calculating magnetic bearings. To do this you begin by laying your hiking compass alongside each line segment in your route; taking care that the direction of travel arrow correctly points in the actual direction of travel. You turn the bezel on your compass until the orienting arrow points to True north and the orienting lines are parallel with the nearest longitude line. You read the chart bearing from where the index line intersects with the bezel. In Figure 2, this is 190°. This is a chart bearing. You must now convert this reading to a magnetic bearing.
For most regions of the Chesapeake, declination is 11 degrees West. Signing declination, it becomes -11°.
To compute the magnetic bearing for this leg of the paddle, plug the known variables into equation 1 and obtain:
190° (chart bearing) - (-11°) (declination) = 201° (magnetic bearing).
Remember, when subtracting a negative value, you add.
You write this value along the line segment as "201° M" and move onto the next line segment. When you are through, all segments of your journey contain a magnetic bearing.
Using the side of your compass, you next measure the distance between waypoints and convert the measurement to mileage using the distance scale. This is written on the bottom side of each segment. Finally, you are comfortable enough in your calculation that you lead out using your deck compass and wristwatch to guide you.
Let's do a similar problem using an East declination.
Previously we found that the chart bearing for our route through Dana Passage (points A to B in Figure 1) was 62°. Since declination for Puget Sound is 16°, 30' East, we needed to follow a magnetic bearing of:
62° (chart bearing) - (+16.5°) (declination) = 45.5° (magnetic bearing)
In both East and West declination examples we subtracted declination. The difference was that one was positively signed and the other was negatively signed.
In the next example we'll convert compass bearings to chart bearings to find our position en route.
Equation 1 can be used to convert compass bearings to chart bearings. Suppose while paddling from Great Fox Island to Tangier Island, a 5 NM open water crossing in the Chesapeake Bay, you wish to check how far you have to go and if you are still on the plotted course. From your position you can see the water tower on Tangier Island that corresponds to a tower symbol on your chart. You can also see Watts island lying to the south-southeast. Shooting bearings on both, you obtain 169° for Watts island and 248° for the Tangier water tower. You write each down in your waterproof notebook. Next, you do some mental arithmetic. Rearranging equation 1 for chart bearings, you arrive at: chart bearing = magnetic bearing + declination. Remembering that for the Chesapeake Bay, declination carries a negative sign, the chart bearing for the water tower is:
248° magnetic + (-11°) (declination) = 237° True.
The chart bearing to Watts island is:
169° magnetic + (-11°) (declination) = 158° True.
To find your position in the bay, you rotate the compass bezel so that the index line points to 158° on the compass bezel. Then you align the orienting lines of the compass so that they are parallel to the lines of longitude on the chart. You reposition the compass edge so that it points to the north end of Watts island and slightly re-adjust the compass to make sure that the orientation arrow points to True north and then draw a line along the compass edge. You follow a similar procedure for the 237° bearing shot on Tangier's water tower.
You may have to extend these lines to their point of intersection, but the result will look similar to that shown in Figure 4. The intersection is your position on Tangier Sound. You have 3 NM to go to Tangier Island. You have drifted south of the plotted course.
All of the examples above assume you have a printed chart available. It can be either a commercially printed chart or a home printed chart. However, if you do your own printing, you should check off each of the items listed below to be certain your chart will be useable. Do this before you laminate it.
1. Declination: If a compass rose does not appear on your chart, write the declination somewhere on your chart. Be sure to include the sign, or at least note if it is East or West. The bottom is preferable, as this is where information is commonly located. Make sure the chart's orientation is intuitive when viewed at first glance. NOAA charts are printed so that True North is always at the top of the chart and all lines of longitudes are vertical. If this is not the case, then add a north/south arrow.
2. Distance Scale: Add a distance scale if one does not appear in your printed version. This is an easily overlooked item on BookletCharts. A penned in scale works very nicely. You'll need it if your charts are not printed to the same scale.
3. Latitude and Longitude Labels: Label all of lines of latitude and longitude on your chart. It isn't necessary to include seconds, but do include both degrees and minutes. You do not want to find yourself in the position of having to call the Coast Guard for an emergency and being unable to determine your location because you failed to label the latitude and longitude lines.
Personalizing your charts
Except on rare occasions, most of my kayaking is done following a shoreline. On not so rare occasions, I find that the feature I'm interested in charting is illustrated on multiple pages of a BookletChart. Usually the shoreline lies near the edge of the page and there is lots and lots of open water on the page. If this happens to you, and I'm sure it will, one solution is to combine the pages. Simply print the pages containing the feature, then cut and paste them back together to highlight the feature on a single page. Using a separate piece of paper as an overlay for sizing, mark off page edges, then cut the new chart to 8.5" x 11" size. You could laminate the chart at this point, but I find that copying the hybrid and then laminating the copy works best. This way I can always go back to the original and make a second copy if needed. Be sure to mark the BookletChart number and the pages from which you took the sections, so that you can find the locale of your custom chart from the original index page at a later time.
Before you laminate your charts, you can do additional customization. For example, mark the location of known put-in sites, possible take-out sites, boat-ramps, good and bad campsites, possible beach sites for lunch landings, and bail points. Some kayakers pencil in pre-measured distances between points of interest and the circumferences of islands. Regarding the latter, circle these distance measures to denote their special significance. I do this on charts for areas I frequent regularly. This will save you time if you have to make changes to your original route.
Marine charts do not contain topographical information. You may wish to add obvious ground features, such as peaks or cliffs if you believe the information will assist fixing a location.
The detail of your chart will be highly dependent on the scale you choose, so if you are printing charts from software, look the printed chart over closely before lamination. Change the scale of the display version and look for details that may be absent from a low resolution image. Important coastal features that are obvious on 1:10,000 scale may disappear on a charted printed using a 1:50,000 scale. You can pencil these features back into your chart before it is laminated and made permanent.
- Tools are available online to print your own, personal navigation charts. These charts are re-usable.
- When plotting routes, convert chart bearings to compass bearings using the algebraic expression:
Magnetic bearing = Chart bearing - declination.
The values for declination used in this equation must be signed. Use negative for West declination and plus for East declination. The equation may be rearranged and solved for Chart bearing when needed.
- Always create user friendly charts. Each chart must include a distance scale, a declination, and properly labeled lines of latitude and longitude.
- Customize your chart before you laminate it. Routes are applied as needed using a china marker so that they may be erased as new routes are plotted. The locations of put-in sites, bail-points, good campsites, and other types of information are your part of your individual knowledge base. They normally do not change. If you add them to the chart, they will be there when you need them next paddle.
1. Nautical Charts can be downloaded as printable BookletCharts from NOAA. They are ideal for kayak use because they may be printed on 8-1/2 X 11 inch paper or photo quality paper.
2. Charts should be laminated to ensure they are not water damaged during use. Scotch makes a very affordable thermal laminator.
Author note regarding lamination: If you intend on punching a hole in your chart for a retainer, consider cutting a notch in the chart itself at the location of the intended hole before you laminate it. This way the two laminating layers will make contact during the heating process. You may punch through the lamination sheet at this spot without exposing the paper chart between the layers. If you fail to do so, water will eventually seep into your chart and cause it's ruin.
3. Coastal Explorer Express, from Rose Point Navigation Systems.
Selected Reading: For more information than you ever wanted to know about navigating a kayak, check out the books and online sources below.
Fundamentals of Kayak Navigation. David Burch
Sea Kayak Navigation. Franco Ferrero.
Sea Kayak Navigation Simplified. Lee Moyer.
Kayarchy - the sea kayaker's online handbook and reference. Sea kayak navigation (2)