What Is Dead Reckoning and How Do You Use It?

Dead Reckoning Principles

Dead reckoning (DR) calculates position from a known starting point using distance traveled, direction, and time. You begin from a confirmed location (your house, last known position from GPS, or a marked checkpoint). As you travel, you track heading direction, distance covered, and time elapsed. Plotting these on a map shows your calculated position.

Distance is typically estimated by counting paces or timing yourself walking at a known speed. A pace is one step from heel to heel—most people average 3 feet per pace. Time lets you calculate speed: if you walk 120 paces per minute and your pace is 3 feet, you’re traveling about 3.5 miles per hour. Direction comes from landmarks, sun position, or a compass if you have one.

Executing Dead Reckoning Navigation

Start at a known position marked on your map. Identify your destination and determine the direction using your map and a reference point (sun, landmark, or compass). Begin walking while counting paces and tracking time. Every 15-20 minutes, note your elapsed time and pace count, calculate distance, and plot your position on the map.

Adjust for obstacles: dead reckoning assumes straight-line travel, but terrain forces detours. When detouring, continue tracking paces and time, then adjust your calculated position to account for the detour. Periodically confirm your position using visible landmarks and map features. Discrepancies show navigation error—correct course and note the error magnitude.

Accuracy and Limitations

Dead reckoning accumulates error—small mistakes in pace counting or direction estimation compound over distance. Even expert navigators expect 10-15% error over long distances. Over one mile, this means 500-800 feet of position uncertainty. Over 5 miles, error grows to 2,500-4,000 feet. Use landmark confirmation regularly to reset your position.

Dead reckoning works best in featureless terrain where landmark navigation is impossible—deserts, snow-covered regions, or heavily forested areas. In terrain with visible landmarks, use landmarks as primary navigation and dead reckoning to confirm. Combining methods provides best navigation accuracy when instruments are unavailable.