Dead reckoning is estimating your current position from a known starting point by tracking the direction (bearing) you've traveled and the distance covered. Combined with timing and pace counting, it lets you navigate when landmarks are hidden — in fog, whiteout, darkness, or featureless terrain — though small errors accumulate, so it's checked against known features.
A grid reference specifies a location on a map using its grid lines, giving numbers read as an easting (across) and then a northing (up) — 'right then up.' Adding more digits increases precision, from a grid square down to a few meters. Grid references let you communicate an exact position quickly, including to rescuers.
UTM (Universal Transverse Mercator) coordinates locate a point using a metric grid, dividing Earth into zones and giving an easting (meters east within the zone) and northing (meters north). Because positions are in meters on a square grid, UTM is easy to plot and measure on a map, which is why many backcountry navigators prefer it to latitude and longitude.
A waypoint is a set of coordinates marking a specific location — a trailhead, junction, campsite, water source, or summit — saved for navigation. On a GPS or mapping app, you string waypoints together into routes and navigate from one to the next, while a recorded path of where you've been is called a track.
True north is the direction to the geographic North Pole, the reference maps are drawn to; magnetic north is the direction a compass needle points, toward Earth's magnetic pole, which lies elsewhere and moves over time. The angle between them is declination — accounting for it is essential to navigate accurately with map and compass.
Declination (magnetic declination) is the angle between magnetic north, where a compass needle points, and true north, used by maps. It varies by location and slowly over time, and ignoring it can put you significantly off course over distance. You correct for it by adjusting your compass or adding/subtracting the local declination from your bearings.
A baseplate compass mounts a rotating magnetic needle and bezel on a flat, transparent plate marked with rulers and direction-of-travel arrow, designed for taking and following bearings off a map. Its declination adjustment and clear base make it the standard navigation compass for hikers and mountaineers — and a Ten Essentials item that never needs batteries.
A bearing is a direction expressed as an angle in degrees clockwise from north (0–360°), used to navigate from one point to another. You can take a bearing off a map and follow it with a compass, or sight a bearing to a landmark in the field — the core skill of map-and-compass navigation.
Map scale is the ratio between a distance on the map and the corresponding distance on the ground, written as a ratio such as 1:24,000 (one unit on the map equals 24,000 units in reality). A smaller second number means a larger-scale, more detailed map covering less area; scale lets you measure real distances and plan travel time.
A contour line on a topographic map connects points of equal elevation, so the pattern of lines reveals the terrain's shape and steepness. Lines close together indicate steep ground; lines far apart indicate gentle slopes. The contour interval — the elevation change between adjacent lines — is given in the map's legend.