A map is a powerful tool because it shrinks the world onto a page or screen while keeping the most important thing: where things are in relation to each other. To use one, you need a few skills: finding an exact location, working out real distances, giving directions, and imagining hills and valleys from flat lines. These skills come up in every unit of this course, from locating landform regions (Unit 2) to mapping population density (Unit 4) and planning communities (Unit 5), and in everyday life whenever you follow a trail map or a phone app. Start with the elements every map needs, listed below.
- Title: what the map shows, where and when ("Population density of Ontario by census division, 2021").
- Orientation: a north arrow, so you know which way the map faces. Most maps put north at the top, but not all do.
- Date: when the data was collected or the map was made.
- Author and source: who made it and where the data came from, so you can judge its credibility.
- Legend (or key): what each symbol, colour and line means.
- Scale: how distances on the map compare to real distances on the ground.
- A useful memory aid is TODALS: title, orientation, date, author, legend, scale (plus sources).
- Every flat map distorts the round Earth in some way. The common Mercator projection keeps shapes and directions correct locally but stretches areas near the poles: Greenland looks about as large as Africa, yet Africa is roughly 14 times bigger, and Canada's Arctic islands look larger than they really are.
Latitude and longitude
- Latitude measures how far north or south of the equator (0°) a place is, up to 90° N or 90° S at the poles. Lines of latitude, called parallels, run east–west and never meet.
- Longitude measures how far east or west of the prime meridian (0°, through Greenwich, England) a place is, up to 180°. Lines of longitude, called meridians, run north–south and meet at the poles.
- Write latitude first, then longitude, always with the direction letters: Toronto is about 43.7° N, 79.4° W. All of Canada is north of the equator and west of the prime meridian, so every Canadian location is "N" and "W".
- A degree can be split into 60 minutes (′): 43.7° is the same as 43° 42′ N, because 0.7 × 60 = 42.
- One degree of latitude is about 111 km everywhere, so distance north–south ≈ difference in latitude × 111 km. Example: two places on the same meridian 3° apart are about 333 km apart.
- A degree of longitude is about 111 km only at the equator. It shrinks toward the poles because the meridians meet there: at Toronto's latitude it is only about 80 km.
Map scale
A ratio scale (or representative fraction) such as 1 : 50 000 means one unit on the map equals 50 000 of the same unit on the ground. To turn it into a statement scale, convert the ground distance to kilometres: there are 100 000 cm in 1 km (100 cm per metre × 1000 m per km), so 50 000 cm = 0.5 km and the statement is "1 cm represents 0.5 km." A scale bar (linear scale) draws that relationship as a ruler, and it stays correct even if the map is enlarged or shrunk on a screen. To find a real distance: measure the map distance, multiply by the ground distance per centimetre, and check the units. A large-scale map (such as 1 : 10 000) shows a small area in great detail; a small-scale map (such as 1 : 1 000 000) shows a large area with little detail. Canada's National Topographic System maps are often at 1 : 50 000 and 1 : 250 000.
Direction, bearings and grid references
| Compass point | Bearing | Opposite point | Bearing |
|---|---|---|---|
| N (north) | 000° | S (south) | 180° |
| NNE | 022.5° | SSW | 202.5° |
| NE (northeast) | 045° | SW (southwest) | 225° |
| ENE | 067.5° | WSW | 247.5° |
| E (east) | 090° | W (west) | 270° |
| ESE | 112.5° | WNW | 292.5° |
| SE (southeast) | 135° | NW (northwest) | 315° |
| SSE | 157.5° | NNW | 337.5° |
The 16-point compass adds in-between points to the eight main ones: NNE is halfway between N and NE. A bearing is more exact: an angle from 000° to 360°, measured clockwise from north. Many maps also carry a grid of numbered squares. A four-figure grid reference names a square: read the easting (the number along the bottom, going east) first, then the northing (the number up the side). A handy rule is "along the corridor, then up the stairs." A six-figure grid reference adds a third digit to each number by estimating tenths of the way across and up the square, pinpointing a spot to within about 100 m on a 1 : 50 000 topographic map, where each square is 1 km across.
Contour lines and slope
A contour line joins points of equal elevation (height above sea level). The contour interval is the difference in height between neighbouring lines, such as 10 m or 100 m. Read them like this: lines close together mean a steep slope; lines far apart mean a gentle slope; a set of closed rings getting smaller means a hill, with the summit inside the smallest ring; contour lines that bend into a V point upstream where they cross a valley or river. Contour lines never cross one another, except at an overhanging cliff. Drawing a profile (side view) along a line, as in the figure, turns these flat lines back into the shape of the land.