# Distance Off and Quick EP’s

by Chris Riley Updated on August 16, 2019. In

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There are many times when knowing the distance off to a fixed object will be of considerable value to the navigator making his way through crowded channels or just cruising off the coast on a sunny afternoon. You may want to print this section out and put it in your navigation notebook for future reference.

What if you were cruising around the Sakonnet River just south east of Sachuest and wanted to make sure you were going to avoid Cormorant Rock (approximately 41º 27.6’N 71º 14.9’W) because you have a fondness for the shape of your keel and don’t really want it altered by running aground…

Try it right now — extend your arm from your position in your chair, hold up your finger and sight off something across the room: your door jamb, a corner, a bookshelf – anything. Now switch eyes and estimate how far your finger moved. Now multiply that by ten and that is your rough distance to that object. Find a measuring tape and check to see how close you were.

As in the example above, you know the distance between the silo and spire is 1.6nm. Your hand is 4 inches across your palm and you are holding it 10 inches from your eye to cover both objects. What is your distance off?

Take 1.6nm (the distance between the charted objects) times 10 (the distance between your hand and eye) and then divide that by 4 (the width of your hand) and you should get 4nm.

Once you have determined your distance off to a charted object, you can put a COP on the chart. Then, take a compass bearing to that same object and place an LOP on the chart. Where the LOP and COP meet is your EP – easy peasy…

Recap: to determine a distance off using the “blink” method:

1. Extend your arm, holding up a pencil or your finger and close the opposite eye.
2. Place the pencil or your finger over the sighting object.
3. Switch eyes, keeping your arm still.
4. Estimate the distance in feet, yards, or miles that the pencil or your finger appeared to move.
5. Multiply this estimate by ten and that is your distance to the object.
6. To estimate your position, draw a COP on your chart based on the distance off you determined above, then take a compass bearing to the sighted object. Where the LOP from your compass bearing meets the COP is your estimated position.

Recap: to determine a distance off using the “hand” method:

1. Using your chart, determine the distance in nautical miles (or statute miles depending on your location) between two visible objects in near proximity.
2. Extend your arm, holding up your hand and close one eye.
3. Move your hand closer to your eye until your hand completely covers both objects (you may have to tuck in some fingers or spread them apart).
5. Measure the width of your hand that it took to cover both objects.
6. Multiply the charted distance by the distance from your hand to your eye, then divide that product by the width of your hand. The answer is your distance off in nautical (statute) miles.
7. To estimate your position, draw a COP on your chart based on the distance off you determined above, then take a compass bearing to the sighted object. Where the LOP from your compass bearing meets the COP is your estimated position.

#### Test your new-found knowledge of quick Distance Off methods.

Using your 1210 TR training chart solve the following problem:

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