An independent reference
Every map is a compromise: the Earth is round, paper is flat, and something — area, angle, distance or direction — has to give. This handbook explains the four things a reader must decode on any topographic sheet: the projection, the contours, the scale and the legend. No products, no services — just the grammar of the map.
| Scale | One centimetre on the map |
|---|---|
| 1:10 000 | 100 metres |
| 1:25 000 | 250 metres |
| 1:50 000 | 500 metres |
| 1:100 000 | 1 kilometre |
| 1:250 000 | 2.5 kilometres |
| 1:1 000 000 | 10 kilometres |
Because a sphere cannot be unrolled into a flat sheet without stretching or tearing, every projection keeps some properties and sacrifices others.
Peel an orange and press the skin flat: it rips at the edges and wrinkles in the middle. A projection is the mathematics that decides where the stretching goes, using a cylinder, a cone or a plane as the transfer surface.
Four properties are at stake — shape, area, distance and direction — and no projection keeps them all. A conformal map keeps local angles but inflates areas; an equal-area map keeps relative size but bends outlines.
The reader's habit is one question: which projection drew this? On a conformal world sheet Greenland rivals Africa, though Africa is roughly fourteen times larger; on an equal-area sheet the honest proportion returns.
These milestones are general cartographic history, included for context; they are not events in the life of this website.
A contour joins every point that sits at the same height above the datum, so a stack of contours is a stack of imaginary shorelines.
Imagine a hill as an island being flooded: each time the water rises by one contour interval it draws a new shoreline, and those shorelines seen from above are the contours. Crowded lines mean steep ground; wide spacing means gentle.
The interval — ten metres on many walking sheets — is printed in the margin, and every fifth line is a heavier index contour carrying a height figure. Count the lines between two points, multiply by the interval, and you have the climb.
Shapes repeat as a vocabulary: closed loops are hills, V-bends point uphill into valleys, an hourglass waist between two summits is a saddle, hachured loops mark depressions, and contours fused into a single line mean a cliff.
Scale is the fixed ratio between a length on the sheet and the length it represents on the ground, and every measurement on the map depends on it.
A representative fraction such as 1:50 000 says one unit on the map equals fifty thousand of the same unit on the ground: a centimetre stands for 500 metres. The same ratio can be written in words or drawn as a graduated bar.
The vocabulary runs backwards from intuition: a large-scale map shows a small area in fine detail, while a small-scale map shows a large area in broad strokes. Read the fraction as a number and let the arithmetic decide.
Only the bar survives copying. Enlarge the sheet on a photocopier and the printed ratio turns false, while the drawn bar stretches with the image and stays truthful — so measure against the bar, not the number.
The list names the kinds of standard references a reader can consult — national mapping agency guides, surveying textbooks and orienteering manuals; this site reproduces no text from them.