Task 4: Relaying Your Position
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So now you know where you are, and how to get to your destination. You jump on your snowmachine (snowmobile for those of you in the contiguous United States). But, alas! You find that you're all out of gas. You now need to call your buddies from town to bring you more. However, in order to do this, you need to be able to tell them where you are with more detail than, "I'm in the woods somewhere southeast of you." An exact position, relative to a known point on the map, is necessary.
You already have your position marked and have checked that your map is still aligned. You will be providing your position as your distance from a defined reference point, along a certain bearing. Therefore, select a point on the map that can be clearly defined which is not easily mistaken for a different location.
So you select a peak on the map. This peak could be described as "the southernmost peak between Iowa Creek and the Little Chena River". You might also want to mention the height is 1205 feet. Follow the steps from Task 3 to get your distance and bearing. The distance is too long for the compass scale to measure, so simply mark 6000 meters at a time along the line and keep measuring. The result comes to 11,600 meters and you're reading an azimuth of 349 degrees. Since there are 100 meters to the kilometer, this 11,600 meters is easier stated as 11.6 kilometers.
Since you're trying to give your bearing from the hill, instead of to the hill, you will need the back azimuth of 349 degrees. Or, in this case, you could simply spin the compass 180 degrees, and measure the azimuth of the line with the compass pointed towards you, from the peak. Either way the result is 169 degrees.
So now you just tell your buddies that you are 11.6 kilometers from that peak, at a bearing of 169 degrees, right?
WRONG! Remember, all your measurements are being made with a compass that uses Magnetic North and is 15 degrees off of True North. In previous examples, this didn't matter because you were using that same compass to find your way to your destination. As long as your map was properly oriented, the errors effectively canceled themselves out. But now, you are trying to give a bearing to be read on a map or GPS, without any compass. Therefore, you must give your bearing relative to True North, which is what the people looking for you will use to measure the bearing from. This is called a 'True Bearing'.
Since the declination in your area is 15 degrees East, you must add 15 degrees to the bearing. If you're in an area with declination to the West, you would subtract instead of add. The true bearing is, therefore, 184 degrees.
You can now call your buddies and tell them you're 11.6 kilometers from the peak, at a bearing of 184 degrees.
There are ways to state your position based solely on the map using coordinates, grid sections, etc. (see our How to Read A Topographic Map article if you want more info). However, while also being a perfectly valid method, this example demonstrates the importance of correcting for declination, any time your're giving a bearing that won't be used with another compass.
If declination had not been adjusted for in this example, the destination that your rescuers would have come to would have been around 3 kilometers (almost 2 miles) eastwards of your actual location, as indicated by the blue line in the image above.