• David Redding

CHAPTER FIFTEEN: Dead Reckoning


I learned to land navigate as a young soldier long before the advent of GPS. Back then (without a satellite to guide your movement with precision) you had to rely on your map and compass and employ the technique of dead reckoning to reach your objective.


The first step of dead reckoning is to plan your movement by plotting a course and distance on the map. With a pencil, you would make tick marks at the designated start point and your ultimate objective and draw a straight line between the two with a ruler. Then, you would use a protractor to find the map heading between the two points. For example, if the line from the start point to the objective ran due north, the map heading would be 360°, which you then had to convert to a compass heading (called an azimuth) using the declination diagram on the map.


This conversion of a map heading to an azimuth was necessary because there is not just one “north”, there are three. First, there is true north at the north pole, the place on the Earth where all longitudinal lines converge. Then there is grid north, which is the mathematical projection of true north that results from the grafting of the Earth’s spherical surface onto the map’s flat surface. Finally, there is magnetic north, which is the location on the Earth at which your compass’ north-seeking arrow points—which is northerly, but not exactly toward true north. As a result, when you say, “due north”, the direction you are talking about depends upon which of the norths you are referencing.


It also depends upon where you are, because the variance between the three norths changes by location, which is why every map must have its own declination diagram that expresses (in terms of an angle) the particular variance between grid and magnetic north at that spot on Earth. To properly calculate your azimuth, you must apply this grid-magnetic-angle to convert your map heading into a compass heading. Because the azimuth is what defines your course when you are moving through the woods, you would get lost otherwise because grid north and magnetic north are almost never the same place. A map heading of 360° would give you an azimuth of (say) 345°.


After you calculated your azimuth to the objective from the start point, you would estimate the distance between the two by measuring the length of the line you drew on the map and converting that to ground distance using the map’s scale. The scale of a typical military map is 1/50,000, which means that every centimeter on paper equates to roughly 500 meters on the ground. So, if my line was four and a half centimeters long on the map, the estimated distance I would have to move on the ground to get to my objective would be 2,500 meters.


I say “estimated” here because distance, like the heading, is never the same on the map as it is on the ground. The line you measured on the map was smooth, even, and direct, but the line you walked in the woods was over uneven ground that impeded movement. It was anything but smooth, even, and direct. Nothing in nature is.


Nor could you measure it with precision on the ground because there is no such thing as a giant tape measure. Instead, you had to keep track of your distance with your feet using a pace count, which is different for every man. Mine was sixty-two steps per 100 meters, meaning that I theoretically would have to walk off 1,550 steps to move two and a half kilometers. Because the accuracy of that measurement was largely dependent upon the evenness of my stride, the unevenness of the ground upon which I moved would compromise the accuracy of my count.


Putting those two things together, the pace count and the azimuth, I would start off knowing that I would have to walk 1,550 steps at 345° to reach my objective. Because I couldn’t see the full two and a half kilometers from my start point, particularly where the vegetation was thick and visibility was limited, I would “shoot” a 345° azimuth with my compass for a shorter distance to a terrain feature (like a rock outcropping or lightning-mangled tree) that I could see, and use that as a waypoint on my course. Once I reached it, I would shoot to another waypoint at 345° and repeat the process as many times as necessary until I reached my objective.


That’s dead reckoning in a nutshell. While it works well in theory, in practice there were always externalities (in addition to the uneven ground) that would adversely impact the accuracy of my azimuth and pace count.


For instance, there were times when there were no visible waypoints, particularly at night. If that happened, I couldn’t shoot an azimuth to a waypoint but rather had to follow the needle on my compass, which is an imperfect tool because the needle fluctuates during movement. This added stress, which also had an adverse impact.


There was also the externality of obstacles. The straight line I drew on my map was never something I could perfectly follow on the ground because there are no straight lines in nature. There were always small obstacles like boulders or trees that I would have to step around, or large ones like ravines or swamps that I could not directly traverse. Obstacles on the ground cannot be crossed the way they can be drawn over on the map—they must be circumvented. That would push me off my azimuth and frustrate my pace count.


As a result, even though the technique was called dead reckoning, the result was never dead on because the externalities of limited visibility, stress and obstacles always combined to compromise my movement. It didn’t matter how carefully I planned it on the map, or how hard I tried to maintain my azimuth and pace count on the ground, I never emerged precisely at my ultimate objective. Due to externalities, I would always have to do a bit of searching to find it.


I learned three lessons from my years of dead reckoning that have helped me immensely in my life as a Minivan Centurion, even though they have nothing to do with land navigation.


The first lesson is that a man must always be ready to adapt to unexpected circumstances. To achieve anything in life he must first identify his ultimate objective and then plot the course and distance he must travel to get there. Without a plan he will never leave the start point. But in making his plan, a man must always anticipate that it will be impacted and altered by the externalities he will face when he sets it in motion, just as a soldier’s azimuth and pace count are frustrated by the limited visibility, stress, and obstacles that he encounters on the ground. A Minivan Centurion must always have a plan, but he can never hold on to it too tightly because plans are just one of the ways that men make the Creator laugh. Only if he is ready to adapt will a man be able to laugh along with God, keep moving toward the ultimate objective and remain an asset.


The second lesson is that the life of a man is a compromised adventure. As boys, we all start out with a vision of true north in our hearts that was planted there by the Creator when he formed us in his image. But just as a map is an imperfect two-dimensional projection of the three dimensions of Earth, we are mere flawed versions of our Creator because we (unlike Him) are beset by sin in a fallen world. As such, we may yearn for true north in our hearts, but it is grid north by which we are governed. Purposeful Mud that we are, we cannot hope to be perfect during our brief compromised adventure on this mortal coil. Knowing that, the Minivan Centurion stays in the fight and keeps moving toward the ultimate objective set out for him, accepting that he will be forced by externalities to compromise along the way.


The final lesson is that a man must always be prepared to keep searching for his ultimate objective regardless of how careful his navigation has been. In fact, he may find that the tick mark he made on the map before he started his journey was never even the objective at all, but rather just another waypoint along the path to his destination. As a result, the Minivan Centurion is a man who is prepared to keep moving even if he thinks he has arrived. He knows that regardless of his age or station in life, a man’s compromised adventure doesn’t end until the Creator determines it to be so, or he quits and lets his Three Dots fade to black.


And quitting is not an option for the Minivan Centurion. He is a man who presses relentlessly forward on the azimuth set out for him by the Creator. He stays in the fight until the sword is tugged gently from his failing hands so that his spirit may be welcomed home, his purpose accomplished, and his flesh returned to the mud from which it was formed.