Overlanding Essentials: Navigating with Map and Compass
Updated October 2026.
A GPS unit or phone app is the quickest way to follow a track, but it runs on batteries and can break when it hits the floor. A paper map and a baseplate compass need no signal and no charging. Here is what to carry and how to use it.
Quick pick: map, compass or GPS?
| Tool | Tells you | Needs power | Watch out for | Use it for |
|---|---|---|---|---|
| Paper map (topo plus MVUM) | Terrain, roads, water and which routes are open to vehicles | No | Older maps can show old roads and an outdated declination | Planning, the big picture, checking a route is legal |
| Baseplate compass | Direction, as a bearing in degrees | No | Steel and vehicles pull the needle. Declination must be set or worked out | Orienting the map, unsigned junctions, scouting on foot |
| GPS unit or phone app | Your position and the track you drove | Yes | Dead batteries, drops, and a datum that doesn't match your paper map | Tracking where you are and logging the route |
The maps worth carrying
- USGS 7.5-minute topo. Scale 1:24,000, so 1 inch on the map is 2,000 feet on the ground. Free to download from the USGS.
- Motor Vehicle Use Map (MVUM). Shows which national forest roads and trails are open to motor vehicles, by vehicle class and season. If a route isn't on it, it isn't open to motorized travel, even if it looks drivable. Free on each forest's website under Visitor Maps and Guides. Get the current one before each trip.
- Forest visitor map. MVUMs are black and white with no terrain shading, so the Forest Service suggests pairing one with a visitor map or another detailed map.
Reading a topographic map
Start with the legend: scale, contour interval (the height between lines), map datum and declination. Contour lines join points of equal elevation.
- Lines close together: steep ground. A road through tight lines is a steep grade.
- Lines far apart: gentle ground.
- V pointing uphill: a valley or drainage, which can mean a wash or soft crossing after rain.
- V pointing downhill: a ridge.
- Small closed circles: hilltops.
Measure with string
Lay a piece of string along the road on the map, then straighten it against the scale bar. Add 5 to 10 percent for curves and switchbacks the map can't show.
Compass basics and the two norths
- Baseplate with a direction of travel arrow
- Rotating housing marked in degrees, with an index line where you read the bearing
- Orienting arrow and lines inside the housing
- Magnetic needle, red end pointing to magnetic north
Maps are drawn to true north, the direction of the geographic North Pole. The needle points to magnetic north, which is somewhere else. A USGS topo shows both in the margin: a star for true north and MN for magnetic north.
Declination: the gap between true and magnetic north
The angle between true north and magnetic north is declination. It depends on where you are and changes slowly over time, so the number printed on an older map may be out of date. If the needle points east of true north, that's east declination. West of true north is west declination. NOAA shows east as positive and west as negative. Much of the western US has east declination, and in parts of the West it's more than 10 degrees.
Get the current number
Look up your area with the NOAA declination calculator before the trip and write it in the margin of your map.
Easiest fix: set it on the compass. Many baseplate compasses adjust with a small screw or by turning part of the housing. Once set, compass bearings match the map and there's no math in the field.
No adjustment? Work it out by hand:
| Declination | Map to compass | Compass to map |
|---|---|---|
| East | Subtract it | Add it |
| West | Add it | Subtract it |
Small errors add up
The National Wildfire Coordinating Group notes that 1 degree off can put you 920 feet off course in 10 miles. Ignore 10 degrees of declination and you can miss by more than a mile.
Orienting the map
An oriented map lines up with the land, which settles most questions at unsigned junctions. With declination set:
- Turn the housing until N sits at the index line.
- Lay the baseplate edge along a north and south line on the map, direction of travel arrow toward the top.
- Turn map and compass together until the red needle sits inside the orienting arrow. This is called boxing the needle.
Taking and following a bearing
From the map
- Lay the baseplate edge from where you are to where you're going, direction of travel arrow toward the destination.
- Turn the housing until its orienting lines run parallel to the map's north and south lines, N toward the top of the map.
- Read the bearing at the index line.
- Hold the compass flat and turn your whole body until the needle is boxed. The direction of travel arrow points the way.
From the land
Point the direction of travel arrow at a landmark, turn the housing until the needle is boxed, and read the bearing.
Step away from the rig
Vehicles, rebar, fences, clipboards, belt buckles, glasses and rings can all throw off the needle. Walk away from your truck before you take a bearing, and take each one twice.
Following it, and getting back
- Sight along the bearing to a tree, boulder or bend, go to it, then sight the next one. Don't walk staring at the needle.
- Back bearing: under 180 degrees, add 180. At 180 or more, subtract 180. Out at 60 means back at 240.
- At an unsigned junction, take a bearing down each road and compare it with the map before you pick one.
Aiming off, obstacles and triangulation
- Aim off. An error of 3 to 5 degrees is common. Heading for a point on a road, stream or trail? Aim to one side on purpose, so you know which way to turn when you hit it.
- Box around obstacles. Turn 90 degrees and count paces, walk past on your original bearing, then turn back 90 degrees and walk the same count. A pace is two natural steps, counted each time the same foot lands.
- Triangulate to find yourself. Take bearings to two landmarks you can see and find on the map, ideally about 90 degrees apart. Draw a line from each landmark along its back bearing. You are where the lines cross. A third landmark is a good check.
Map, compass and GPS together
- Before you leave, mark your route, bail out roads, fuel and water on the paper map, and note the declination.
- To plot a GPS position on paper, set the GPS to the same coordinate format and datum printed on the map. Older topos often use a different datum than a GPS does by default.
When visibility drops
Fog, dust, snow and darkness hide your landmarks. Shorten each leg and sight to the nearest object you can see along the bearing. Follow handrails like a road, a fence line or a stream. If you lose confidence in your position, stop and wait to triangulate when it clears.
Practice close to home first: take bearings in a park, learn your pace count, then try a day trip with the GPS along to check your work.
FAQ
Do I need a compass if I have a GPS?
Yes. A GPS needs batteries and can break if it's dropped. A compass needs no power, and with a paper map it still tells you which way to go.
What scale topo map should I carry?
The USGS 7.5-minute map, at 1:24,000, where 1 inch equals 2,000 feet. Current and older editions are free to download from the USGS.
Where do I find the declination for my area?
The NOAA declination calculator gives the current value for any location. The figure in a map's legend can be out of date on older maps, because declination changes slowly over time.
Do I add or subtract declination?
Only if your compass can't be set for it. Going from a map bearing to a compass bearing, subtract east declination or add west declination. Going from compass to map, do the opposite.
Can I take a compass reading next to my truck?
No. Steel and iron pull the needle off, and a vehicle is a lot of steel. Walk away from the rig first, and take each bearing twice.
How do I know a forest road is open to my vehicle?
Check the current Motor Vehicle Use Map for that national forest. A route not shown on it is not open to motorized travel, even if it looks drivable, and routes aren't always signed.
Related guides
Sources: Princeton Outdoor Action Backpacker's Field Manual, American Hiking Society, NWCG Basic Land Navigation (PMS 475), NOAA NCEI and USDA Forest Service.
Heading out? Pair this with our GPS for overlanding guide so your paper map and your screen back each other up.