Mapwork
Made Easy
Grade 12 Geography | Study notes in plain language
What is inside
1 Map scale
2 Gradient
3 Magnetic declination
4 Cross-section and intervisibility
5 GIS (Geographic Information Systems)
6 Quick formula sheet and practice questions
How to use these notes: read one section, try the worked example without looking at the answer, then
check yourself. Mapwork is a skill, not something to memorise: the more you practise on old 1:50 000 map
papers, the faster you get.
Always check your own textbook and your teacher's method for the exact wording and layout the marking guideline
expects. All numbers in the examples were chosen to be easy to follow.
, 1 Map Scale
What does 1:50 000 mean?
A map is a tiny picture of a huge area, so the map-maker shrinks everything by the same amount. The
scale tells you how much. 1:50 000 means that 1 unit on the map = 50 000 of the same units on the
ground. So 1 cm on the map is 50 000 cm in real life, and 1 mm on the map is 50 000 mm.
Three ways a scale can be shown on a map:
• Ratio (numerical) scale: 1:50 000
• Line (graphic) scale: a ruler-like bar printed on the map with distances in km
• Word scale: '1 cm represents 500 m'
Large scale vs small scale: 1:10 000 is a larger scale than 1:50 000 because the fraction 1/10 000 is
bigger. Large scale = a small area with a lot of detail (like the orthophoto map). Small scale = a big area
with less detail.
How to convert cm to km
To go from centimetres on the map to kilometres on the ground, follow three small steps:
1 Multiply the map distance (cm) by the scale number: cm × 50 000 = ground distance in cm.
2 Divide by 100 to get metres (100 cm = 1 m).
3 Divide by 1 000 to get kilometres (1 000 m = 1 km).
1:50 000 shortcut: map cm × 0.5 = ground km
Why? Because 1 cm × 50 000 = 50 000 cm = 500 m = 0.5 km. For a 1:10 000 map the shortcut is cm × 0.1 = km (1
cm = 100 m).
Worked example 1: map distance to real distance
The distance between two points is 6.4 cm on a 1:50 000 map. How far is it in km?
6.4 cm × 50 000 = 320 000 cm = 3 200 m = 3.2 km (or shortcut: 6.4 × 0.5 = 3.2 km).
Worked example 2: real distance to map distance
A road is 12.5 km long. How long is it on a 1:50 000 map?
12.5 km ÷ 0.5 = 25 cm on the map. (Going the other way, you divide.)
Worked example 3: finding the scale
4 cm on a map represents 2 km on the ground. What is the scale?
Change 2 km to cm: 2 × 1 000 × 100 = 200 000 cm. Scale = 4 : 200 000. Divide both by 4 = 1:50 000.
Calculating area
Convert each side to the real distance first, then multiply. A block of 4 cm × 3 cm on a 1:50 000 map is 2
km × 1.5 km on the ground, so the area is 2 × 1.5 = 3 km². Never multiply by 50 000 once for the whole
area; change each side separately.
How to measure distance on a map with a ruler
• Straight line: place the ruler along the line, read the distance in cm or mm from point to point (start
from 0, not from the edge of the ruler).
Mapwork Made Easy | Grade 12 Geography (CAPS) Page 2
Made Easy
Grade 12 Geography | Study notes in plain language
What is inside
1 Map scale
2 Gradient
3 Magnetic declination
4 Cross-section and intervisibility
5 GIS (Geographic Information Systems)
6 Quick formula sheet and practice questions
How to use these notes: read one section, try the worked example without looking at the answer, then
check yourself. Mapwork is a skill, not something to memorise: the more you practise on old 1:50 000 map
papers, the faster you get.
Always check your own textbook and your teacher's method for the exact wording and layout the marking guideline
expects. All numbers in the examples were chosen to be easy to follow.
, 1 Map Scale
What does 1:50 000 mean?
A map is a tiny picture of a huge area, so the map-maker shrinks everything by the same amount. The
scale tells you how much. 1:50 000 means that 1 unit on the map = 50 000 of the same units on the
ground. So 1 cm on the map is 50 000 cm in real life, and 1 mm on the map is 50 000 mm.
Three ways a scale can be shown on a map:
• Ratio (numerical) scale: 1:50 000
• Line (graphic) scale: a ruler-like bar printed on the map with distances in km
• Word scale: '1 cm represents 500 m'
Large scale vs small scale: 1:10 000 is a larger scale than 1:50 000 because the fraction 1/10 000 is
bigger. Large scale = a small area with a lot of detail (like the orthophoto map). Small scale = a big area
with less detail.
How to convert cm to km
To go from centimetres on the map to kilometres on the ground, follow three small steps:
1 Multiply the map distance (cm) by the scale number: cm × 50 000 = ground distance in cm.
2 Divide by 100 to get metres (100 cm = 1 m).
3 Divide by 1 000 to get kilometres (1 000 m = 1 km).
1:50 000 shortcut: map cm × 0.5 = ground km
Why? Because 1 cm × 50 000 = 50 000 cm = 500 m = 0.5 km. For a 1:10 000 map the shortcut is cm × 0.1 = km (1
cm = 100 m).
Worked example 1: map distance to real distance
The distance between two points is 6.4 cm on a 1:50 000 map. How far is it in km?
6.4 cm × 50 000 = 320 000 cm = 3 200 m = 3.2 km (or shortcut: 6.4 × 0.5 = 3.2 km).
Worked example 2: real distance to map distance
A road is 12.5 km long. How long is it on a 1:50 000 map?
12.5 km ÷ 0.5 = 25 cm on the map. (Going the other way, you divide.)
Worked example 3: finding the scale
4 cm on a map represents 2 km on the ground. What is the scale?
Change 2 km to cm: 2 × 1 000 × 100 = 200 000 cm. Scale = 4 : 200 000. Divide both by 4 = 1:50 000.
Calculating area
Convert each side to the real distance first, then multiply. A block of 4 cm × 3 cm on a 1:50 000 map is 2
km × 1.5 km on the ground, so the area is 2 × 1.5 = 3 km². Never multiply by 50 000 once for the whole
area; change each side separately.
How to measure distance on a map with a ruler
• Straight line: place the ruler along the line, read the distance in cm or mm from point to point (start
from 0, not from the edge of the ruler).
Mapwork Made Easy | Grade 12 Geography (CAPS) Page 2
