DSE Geography | Map Reading and Scale: a Tutor Lesson Plan

DSE Geography | Map Reading and Scale: a Tutor Lesson Plan | Contours, Gradient and Area

2026-11-02

Tutor lesson-prep guides · Secondary Geography

Students can recite 1:20,000 but freeze when asked to turn 3.5 cm into metres. This lesson drills one hand movement, then adds contours, gradient and area.

Objectives — Students can: (1) convert map distance to ground distance at 1:20,000; (2) count contour intervals and compute a gradient; (3) convert map area to square kilometres; (4) tell steep from gentle slopes.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Unit conversion	How many metres in a kilometre	1,000
Percentages	Rise 100 m over 700 m: what gradient	14.3%
Ratio notation	What 1:20,000 means	One unit on paper to 20,000 on the ground

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8	One hand movement	cm x scale / 100 = metres	Three oral conversions
8-22	Distance	1 cm = 200 m	3.5 cm = 700 m
22-34	Contours	20 m per line	5 lines = 100 m
34-46	Gradient	rise / run x 100	14.3%
46-54	Area	1 cm2 = 0.04000000000000001 km2	0.56 km2
54-60	Exit check	Three questions, marked at once	Independent

03 Teaching script (read it out)

Scene 1: Act one: scale is a hand movement, not a formula

At 1:20,000, 1 cm on the map is 20,000 cm on the ground, which is 200 m. So every conversion is one step: centimetres x 200. 3.5 cm becomes 700 m and 4.0 cm becomes 800 m. Make students say “times 200”, never “times 20,000”, because that answer is still in centimetres. Backwards, 700 m on the ground is 3.5 cm on the map.

Ask: 7 cm on the map is how many metres? (1400 m)

Scene 2: Act two: contours say only three things

Each line joins points of equal height and neighbouring lines differ by 20 m (some maps use 10 m, so read the legend). From the 100 m line to the 200 m line you cross 5 lines, a rise of 100 m. Close lines mean steep, wide spacing means gentle, and a V pointing uphill is a valley. Gradient: 100 m rise over 700 m of ground is 14.3%, about 1 in 7, or an angle of 8.1 degrees.

Force students to separate percentage gradient from angle; the units are different and both are marked.

Scene 3: Act three: area is squared, and that is where marks are lost

1 cm represents 200 m, so 1 cm2 represents 200 x 200 = 40,000 m2, which is 0.04000000000000001 km2. A 3.5 by 4.0 cm rectangle is 14.0 cm2, giving 0.56 km2. The wrong route multiplies 700 by 800 to get 560,000 and then forgets to divide by one million, so the unit is wrong even though the arithmetic looks right.

Every answer must carry a unit; no unit counts as wrong.

04 Question types and worked steps

Type	Example	Steps	Answer
Distance	3.5 cm at 1:20,000	x 200, then / 1,000	0.70 km
Gradient	100 m rise over 700 m	rise / run x 100	14.3%
Area	14 cm2 on the map	x 0.04000000000000001 km2	0.56 km2
Relief	What close contours mean	Steep slope, fast runoff	Read with the V rule

Sanity check (teach this): Always read the legend before converting: 1:20,000 is common in Hong Kong but an exam may use 1:50,000, so recompute the factor as 20,000 / 100 instead of memorising 200. Give gradient either as a percentage or as an angle, never both, and always give area in squared units.

05 Independent practice (3 questions)

Question	Answer	What to watch
3.5 cm at 1:20,000 in metres	700 m (0.70 km)	Did they divide by 1,000
Gradient of 100 m over 700 m	14.3%	Did they multiply by 100
Ground area of 3.5 by 4.0 cm	0.56 km2	Did they square the scale

06 Common mistakes and what to say

Mistake	Student writes	Say this
Multiplying by 20,000	Writes “3.5 cm = 70,000”	“Seventy thousand what: centimetres or metres?”
Forgetting to square area	Answers 14 x 200 = 2,800 m	“Length takes one multiplication, area takes two.”
Gradient given as an angle	Writes “gradient 14.3 degrees”	“The question asks which one: percent or degrees?”
Reading a V as a ridge	Says a V points to a ridge	“Water flows downhill, so the V points upstream: valley.”

07 Homework (paper, section and question numbers)

Secondary Geography chapter index (includes this chapter) — Independent practice questions 1 to 3 on this page
DSE lesson-prep overview and course map — All subject chapters

08 Exit check (last 5 minutes)

Question	Answer	Decision
3.5 cm at 1:20,000 in metres	700 m	Three correct moves on to rocks and weathering
Gradient of 100 m over 700 m	14.3%	One wrong means re-teach the formula
What close contours mean	Steep slope and fast runoff	Two wrong means replay act two

09 Tutor FAQ

Must students memorise Hong Kong map scales?

No, but they should recognise 1:20,000 and 1:50,000 and recompute the factor each time.

Is one decimal place enough for gradient?

Yes, and 1 in 7 is equally acceptable; the unit and the steps are what is marked.

Can area be left in square metres?

It can, but if the question asks for square kilometres the conversion is where marks are lost.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.