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Dead reckoning is moving a set distance along a set line. Generally, it involves moving so many meters along a set line, usually an azimuth in degrees. There is no accurate method of determining a direction in a moving vehicle. A magnetic vehicle-heading reference unit may be available in a few years; for now, use a compass.
a. With Steering Marks. This procedure is the same for vehicle travel as on foot.
(1) The navigator dismounts from the vehicle and moves away from the vehicle (at least 18 meters).
(2) He sets the azimuth on the compass and picks a steering mark (rock, tree, hilltop) in the direction on that azimuth (Figure 12-4).
(3) He remounts and has the driver identify the steering mark and proceeds to it in as straight a line as possible.
(4) On arrival at the steering mark or on any changes in direction, he repeats the first three steps above for the next leg of travel.
Figure 12-4. Determining an azimuth, dismounted.
b. Without Steering Marks. This procedure is used only on flat, featureless terrain.
(1) The navigator dismounts from the vehicle, which is oriented in the direction of travel, and moves at least 18 meters to the front of the vehicle.
(2) He faces the vehicle and reads the azimuth to the vehicle. By adding or subtracting 180º, he determines the forward azimuth (direction of travel).
(3) On order from the navigator, the driver drives on a straight line to the navigator.
(4) The navigator remounts the vehicle, holds the compass as it will be held while the vehicle is moving, and reads the azimuth in the direction of travel.
(5) The compass will swing off the azimuth determined and pick up a constant deviation. For instance, say the azimuth was 75º while you were away from the vehicle. When you remounted and your driver drove straight forward, your compass showed 67º. You have a deviation of -8º. All you need to do is maintain that 67º compass heading to travel on a 75º magnetic heading.
(6) At night, the same technique can be used. From the map, determine the azimuth you are to travel. Convert the grid azimuth to a magnetic azimuth. Line the vehicle up on that azimuth, then move well in front of it. Be sure it is aligned correctly. Then mount, have the driver move slowly forward, and note the deviation. If the vehicle has a turret, the above procedure works unless you traverse the turret; this changes the deviation.
(7) The distance factor in dead reckoning is easy. Just determine the map distance to travel and add 20 percent to convert to ground distance. Use your vehicle odometer to be sure you travel the proper distance.
Another method, if you have a vehicle with a stabilized turret, is to align the turret on the azimuth you wish to travel, then switch the turret stabilization system on. The gun tube remains pointed at your destination no matter which way you turn the vehicle. This technique has been proven; it works. It is not harmful to the stabilization system. It is subject to stabilization drift, so use it for no more than 5,000 meters before resetting.
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If you have to take the turret off-line to engage a target, you will have to start all over, re-do the entire process. |
Return to Mounted Navigation
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Books
Buy the book this website is based on: Map Reading and
Land Navigation
This website is based on the US Army Field Manual: "Map Reading and Land Navigation"
Buy a copy from Amazon.com to take with you out in the field.
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One of the best ways to learn and become proficient in any subject is to find a way to make a game or sport of it. That's exactly what orienteering does! Orienteering began to develop almost 100 years ago in the Scandinavian countries as a fun and effective method for military training in land navigation. Bjorn Kjellstrom was closely involved with the early development of orienteering, and he is the person who introduced the sport to North America. He, along with his brother Alvar, and a friend named Gunnar Tillander, invented the modern orienteering compass. They manufactured and marketed it as the Silva Protractor compass. This compass, along with Bjorn's book Be Expert with
Map and Compass, made it much easier for anyone to learn how to use a map and compass.
This book has become the most widely read classic on the subject of map reading, compass use, and orienteering. Over 500,000 copies have been sold in the english language editions alone. There have been very successful editions published in French, Italian, and other languages as well. It is a short (just over 200 pages), easy to read, enjoyable book that can help you to have fun while you learn the subject quickly and effectively.
The book is organized into four main parts, plus a short, useful introduction. Part 1 covers having fun with maps alone. Then, Part 2 covers having fun with a compass alone. Part 3 puts it together and shows you how to have fun with a map and compass together. This section also introduces the game or sport of orienteering. Part 4 covers competitive orienteering for those who would like to compete with others in the sport.
A reproduction of a segment of an actual topographic map is included as a fold-out in the back of the book. It is used together with the "how-to" instructions the book provides. For example, one of the exercises in Part 3 is an imaginary orienteering "hike" that uses the sample map.
If you would like to have one of the best books available on map reading and using a compass,
Be Expert with
Map and Compass is hard to beat. You can buy a copy from Amazon.com today.
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