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- Scale, distance and contour lines
Scale, distance and contour lines
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A map shrinks the real world. Scale tells you by how much, and contour lines show the shape and height of the land.
Reading a scale
A ratio scale such as 1:25,000 means 1 cm on the map is 25,000 cm on the ground.
25,000 cm = 250 m = 0.25 km. So on a 1:25,000 map, 4 cm = 1 km.
On a 1:50,000 map, 1 cm = 50,000 cm = 0.5 km, so 2 cm = 1 km.
A line scale (scale bar) lets you measure a distance with a ruler or a strip of paper and read it off directly.
25,000 cm = 250 m = 0.25 km. So on a 1:25,000 map, 4 cm = 1 km.
On a 1:50,000 map, 1 cm = 50,000 cm = 0.5 km, so 2 cm = 1 km.
A line scale (scale bar) lets you measure a distance with a ruler or a strip of paper and read it off directly.
Working out distances
Real distance = map distance × scale. Then convert units: 100 cm = 1 m and 1,000 m = 1 km, so 100,000 cm = 1 km.
Example: 6 cm on a 1:50,000 map = 6 × 50,000 = 300,000 cm = 3 km.
For a winding road or river, lay string or the edge of a paper strip along the route, then measure it against the scale.
Example: 6 cm on a 1:50,000 map = 6 × 50,000 = 300,000 cm = 3 km.
For a winding road or river, lay string or the edge of a paper strip along the route, then measure it against the scale.
Contour lines and height
Contour lines join places at the same height above sea level, usually shown in metres.
The contour interval is the height gap between neighbouring lines, for example 10 m.
Close together = steep slope. Far apart = gentle slope. No contours = flat land.
A spot height is a dot with an exact height written beside it. A triangulation pillar marks a high point.
The contour interval is the height gap between neighbouring lines, for example 10 m.
Close together = steep slope. Far apart = gentle slope. No contours = flat land.
A spot height is a dot with an exact height written beside it. A triangulation pillar marks a high point.
On a 1:25,000 map, a footpath measures 10 cm. How long is it in km?
- Multiply: 10 × 25,000 = 250,000 cm.
- Convert: 250,000 ÷ 100,000 = 2.5 km.
Answer: 2.5 km
Ratio scale: 1:25,000 means 1 cm = 0.25 km (4 cm = 1 km); 1:50,000 means 1 cm = 0.5 km (2 cm = 1 km). Real distance = map distance × scale, then ÷ 100,000 for km. Close contours = steep.
The interactive lesson includes the diagrams for this topic.
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