54.5°N 3.2°WScafell Pike, England
The parts of a map
Before you look at the map itself, read the margin. It usually holds the title, the legend (or key) explaining each symbol, the scale, a north arrow or note on north, the grid system, the contour interval and the date the map was surveyed or revised. An old map may miss new roads or paths, so the date matters.
How map scale works
Scale tells you how much the real world has been shrunk. A scale of 1:50,000 means one unit on the map equals 50,000 of the same unit on the ground, whatever the unit. Maps also show scale as a bar you can measure against, which stays correct even if the map is printed larger or smaller.
| Scale | 1 cm on the map | 1 inch on the map | Typical use |
|---|---|---|---|
| 1:10,000 | 100 m | 833 ft | Town plans, orienteering |
| 1:24,000 | 240 m | 2,000 ft | USGS topographic quadrangles |
| 1:25,000 | 250 m | 2,083 ft | Detailed walking maps |
| 1:50,000 | 500 m | 4,167 ft | Hill walking and regional travel |
| 1:250,000 | 2.5 km | about 3.9 mi | Road atlases and touring |
| 1:1,000,000 | 10 km | about 15.8 mi | Country and wall maps |
A "large-scale" map shows a small area in great detail, like 1:10,000. A "small-scale" map shows a large area with less detail, like 1:1,000,000. The names feel backward, but they come from the size of the fraction: 1/10,000 is a larger number than 1/1,000,000.
Measuring distance
- For a straight line, lay a ruler or the edge of a sheet of paper between the two points and compare the length with the scale bar.
- For a winding path, lay a piece of string along it, then straighten the string against the scale bar.
- Add time for climbing. Steep ground slows walkers far more than distance alone suggests, which is where contour lines come in.
Grid references
Many maps are printed with a square grid, and each line has a number. To give a grid reference, read the number of the vertical line on the left of your square first (the easting), then the horizontal line below it (the northing). A common memory aid is "along the corridor, then up the stairs." Splitting each square into tenths by eye gives a more precise six-figure reference.
Three kinds of north
| North | What it points to |
|---|---|
| True north | The geographic North Pole, along the meridians |
| Grid north | The direction of the vertical grid lines on the map |
| Magnetic north | Where a compass needle points, which wanders slowly over time |
The angle between true north and magnetic north is called declination. It differs from place to place and changes from year to year. Many maps print it in the margin with the year it applied. For a current value, use an official geomagnetic calculator such as the one published by NOAA, and adjust your bearings by it.
Orienting the map
A map is easiest to read when it is turned to match the land in front of you. Without a compass, line up a road, river or ridge on the map with the real one. With a compass, lay it on the map, turn the map until the grid lines run parallel to the needle, and allow for declination.
Taking a bearing with a baseplate compass
- Put the edge of the compass along the line from where you are to where you want to go, with the direction arrow pointing toward the goal.
- Turn the dial until its orienting lines run parallel to the map's north-south grid lines, with north on the dial pointing to the top of the map.
- Adjust for declination as the map or a current source tells you.
- Hold the compass flat, turn your body until the needle sits inside the orienting arrow, and walk where the direction arrow points.
On a hike, carry a paper map and compass as well as your phone. Batteries and signal both run out, often at the worst moment.
Map reading FAQ
What scale should I use for hiking?
1:24,000 or 1:25,000 shows paths, walls and small streams. 1:50,000 covers more ground on one sheet and works well for longer routes or open hills.
Do I need to worry about declination?
Over a short walk in a place where declination is small, the error may not matter. Where it is several degrees, ignoring it can put you hundreds of meters off over a few kilometers, so it is worth the adjustment.
What is the difference between a legend and a key?
Nothing. Both words mean the box explaining the map's symbols and colors.