Map, Compass & Dead Reckoning

Overview

Navigation is a chain: orient the map, choose a line, follow it with a compass and terrain features, and keep track of distance and time. Use redundant methods—if one link breaks, the others keep you honest.

Skill Level: Basic–Intermediate

Bearings

Two common tasks: ground→map and map→ground.

Ground to map (resection)

Sight a landmark with your compass; note the magnetic bearing.
Add declination to convert to a true bearing (see Declination). Subtract 180° (back‑bearing) to project from the landmark toward you.
Draw that line on the map through the landmark. Repeat with a second landmark; the intersection ≈ your position.

Map to ground

On the map, draw a line from your position to your target; read the true bearing.
Convert true→magnetic by subtracting declination (east positive; west negative). Set that bearing on your compass and follow it by sighting a distant feature; walk to it; repeat.

Back‑bearing to check drift

If following a bearing, turn around and check the bearing is ±180° from your set course (mod 360°). Large differences signal drift or interference.

Declination

Magnetic north ≠ true north. Declination is the angular difference (east positive, west negative) between them at your location.

Simple conversions

Magnetic → True: True = Magnetic + Declination
True → Magnetic: Magnetic = True − Declination

Examples

Declination = +12° (east). Magnetic 70° → True 82°. True 250° → Magnetic 238°.
Declination = −8° (west). Magnetic 70° → True 62°. True 250° → Magnetic 258°.

⚠️ Caution: Know whether your compass has adjustable declination. If it’s set in the baseplate, don’t do math twice. 📝 Note: Declination shifts over time. Check your local value annually and update your compass/baseplate notes; many topo maps show the year and annual change. 💡 Link: NOAA Magnetic Declination Calculator — https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml (check yearly and set adjustable compasses accordingly). ⚠️ Caution: Keep compasses away from ferrous metal, vehicles, and phones when taking bearings. Step 3–5 m away, level the compass, and re‑check to avoid magnetic interference.

Triangulation

Fix your position by intersecting lines from two (ideally three) known points.

Two‑point resection (compass method)

Pick two distinct landmarks visible to you and identifiable on the map (peaks, towers).
Take magnetic bearings to each; convert to true; subtract 180° to form back‑bearings.
Draw both back‑bearings from the landmarks; the intersection is your position (or a small triangle—your error zone).

Three‑feature resection (map method)

Align map to terrain (orient map using compass and terrain features).
Identify three features around you; draw rays toward them along your sight lines. Intersection area is your position.

Pace Count Beads

Track distance accurately without electronics.

Setup

Know your 100 m pace on flat, trail, and rough terrain (calibrate as in Timekeeping Without a Clock).
Beads: Ten lower beads (each = 100 m) and four upper beads (each = 1 km). After 10 lowers, slide one upper and reset lower beads.

Usage

Slide one lower bead each 100 m; at 1 km, reset lowers and slide one upper.
Record terrain changes and bearing checks at each kilometer in a small log.

💡 Tip: Quick time estimate with Naismith’s Rule (on foot): ~1 hour per 5 km plus ~1 hour per 600 m of ascent (adjust for load, terrain, and fitness).

Terrain Association

Use visible features to confirm your location constantly.

Contours: Ridges, saddles, spurs, reentrants—match their shape and spacing to the map.
Water: Streams, lakes, marshes—note flow direction and confluences.
Man‑made: Roads, powerlines, buildings—use as handrails or backstops.

Handrails

Follow nearby linear features that run roughly along your desired direction.

Natural: Rivers, shorelines, ridgelines.
Man‑made: Roads, fences, pipelines.
Offset technique: Intentionally aim to one side of a handrail (attack point) so you know which way to turn when you hit it.

Backstops

Pick an obvious feature beyond your target so you know when you’ve gone too far.

Examples: A road crossing the trail, a stream bend, a cliff line.
Set a time/distance backstop too (e.g., “If not there in 30 minutes, turn back”).

Attack Points

Navigate first to an easy, nearby feature, then make a short, precise leg to the target.

Example: Reach a stream–trail junction (attack point), then follow a 310° bearing for 400 m to a campsite.

☑️ Checklist — Simple Nav Plan

Start/known point and time logged
Target and attack point defined
Bearing(s) and declination noted (true and magnetic)
Distance (pace beads) and time estimate
Handrails/backstops identified
Contingency if off‑course (stop, resection, or return to last known point)

Examples

Low‑viz forest: Handrail along a stream (flowing N→S), attack point at a distinctive bend, then 600 m on 085° magnetic to a cabin.
Open terrain: Follow a fence line (handrail) 1.2 km, then use a 200 m 270° leg to a tank. Backstop is the cross‑fence beyond.

Key Takeaways

Convert bearings correctly; write both true and magnetic to avoid mental math in the field.
Use handrails and attack points to reduce error; set backstops to prevent overshoot.
Keep a running log of bearings, distances, and times; it’s your breadcrumb trail.

Scenario

🧭 Scenario (Whiteout timberline): Trail vanishes; you can see two distinct peaks briefly through clouds.
🔍 Decisions: Wander vs resection; write bearings or keep in head.
✅ Outcome: You take two magnetic bearings, convert to true, draw back‑bearings, and fix position in a small triangle; you choose a handrail to a shelter.
🧠 Lessons: Resection > wandering; write both true/mag
🏋️ Drill: Do a two‑point resection at a city park.