Frostbite is a localized cold injury in which skin and underlying tissue freeze, most often affecting the fingers, toes, ears, nose, and cheeks. It progresses from reversible frostnip through superficial to deep frostbite, which can cause permanent tissue damage. Unlike hypothermia — a whole-body emergency — frostbite is a local injury, though the two often occur together.
Hypothermia is a dangerous drop in core body temperature below about 95°F (35°C), caused when the body loses heat faster than it can produce it — often from cold, wet, and windy conditions. Early signs include intense shivering, clumsiness, and confusion; severe hypothermia is life-threatening and requires rewarming and urgent medical care.
A pace count is a navigation technique for estimating distance traveled on foot by counting your steps (usually counting every other step — one count per two steps) over a known distance, then using that calibrated count to measure unknown distances. By knowing how many paces it takes you to cover, say, 100 meters, you can track distance when navigating — especially useful in poor visibility or featureless terrain as part of dead reckoning.
Dead reckoning is a navigation technique for estimating your current position by tracking the direction you've traveled (bearing), your speed or pace, and the time elapsed from a known starting point. By combining a bearing with distance traveled (often measured by pace counting), a navigator can estimate where they are without visible landmarks — invaluable in whiteouts, fog, dense forest, or featureless terrain. Errors accumulate, so it's used carefully and checked against known features.
A grid reference is a set of numbers (and sometimes letters) that identifies a specific location on a map by referring to the map's grid lines — the evenly spaced vertical lines (eastings) and horizontal lines (northings) overlaid on it. By reading eastings first, then northings ('along the corridor, up the stairs'), and estimating tenths within a grid square, you can give a precise location, such as a six-figure grid reference pinpointing a spot to within about 100 meters.
UTM (Universal Transverse Mercator) coordinates are a global position system that divides the Earth into numbered zones and locates any point within a zone using metric eastings (meters east) and northings (meters north). Because UTM uses simple meter-based grid numbers rather than degrees, it's straightforward to plot and measure on a map, and is favored by many backcountry navigators and search-and-rescue teams for its precision and ease of use with a gridded topographic map and GPS.
A waypoint is a specific location defined by coordinates and stored for navigation — a marked point such as a trailhead, junction, water source, campsite, or summit. In GPS devices and apps, waypoints let you navigate toward a saved spot and string points together into a route. They are a core building block of digital and map-based navigation.
True north is the direction along the Earth's surface toward the geographic North Pole — the fixed point around which the planet rotates. Maps are oriented to true north, but a magnetic compass points to magnetic north, a separate, slowly moving location. The angular difference between them is declination, which navigators must account for to translate accurately between map and compass.
Declination (magnetic declination) is the angular difference between true north (the direction to the geographic North Pole) and magnetic north (the direction a compass needle points). Because the two rarely coincide, navigators must account for declination — which varies by location and slowly changes over time — to convert accurately between compass bearings and map directions. Ignoring it leads to significant navigational errors.
A baseplate compass is a compass mounted on a flat, transparent rectangular plate, designed to be used together with a map for navigation — taking and following bearings, measuring distances, and orienting the map. Its clear baseplate (with a direction-of-travel arrow, ruler edges, and a rotating bezel) lets you lay it on a map to plot and transfer bearings. Affordable, lightweight, and reliable, the baseplate compass is the standard navigation tool for hikers and the foundation of map-and-compass work.
