Map Reading & Basic Techniques ! Read and interpret topographical maps

Map Reading & Basic

Techniques! Read and interpret

topographical maps

Understanding our Understanding our environmentenvironment

• Read and interpret physical and human features on topographical maps. • Basic techniques of interpreting and evaluating geographical data, which

may be represented in various forms, such as graphs, photographs and satellite maps.

Make sure you are familiar with the following components of map-reading

Reading Topographical maps1. Map Symbols (Legend) 2. Grid References3. Compass Points 4. Scales (Large Scale/ Small Scale) 5. Reading Contour Lines

What do all the lines What do all the lines

and and symbolssymbols mean?mean?

Reading Topographic

al mapsMap Symbols

(Legend)

Map Symbols (Legend)

How do I find out

How do I find out

wherewhere a particular a particular

landform is found

landform is found

on the map?on the map?

How do I specify How do I specify the the locationlocation of a physical or

of a physical or human feature?human feature?

Northing and Easting Northing and Easting

Eastings are vertical grid lines that increase from west to east.

Northings are horizontal grid lines where their numbers increase from south to north.

Reading Topographical maps

Grid References

Four Figure Grid Reference:

North to South Grid Lines: Eastings

East to West Grid Lines: Northings1521

Six figure grid references

• 180443

• 184441

• 181447181447

• 186448186448

• 188445188445

Reading Topographical maps

Grid References

Six Figure Grid Reference:

North to South Grid Lines: Eastings

East to West Grid Lines: Northings

155217

How to get to How to get to

that place I that place I

want to go to on want to go to on

the map?the map?

Which Which directiondirection

should I go?should I go?

Reading Topographical maps

Compass Points

N

North Point

Cardinal Points 12 Intermediate Points

• North East (NE) • North West (NW) • South East (SE)• South West (SW) • North-North-East (NNE) • East-North-East (ENE) • East-South-East (ESE) • South-South-East (SSE) • South-South-West (SSW) • West-South-West (WSW)• West-North-West (WNW) • North-North-West (NNW) North (N) South (S)North (N) South (S)

East (E) West (W)East (E) West (W)

Determining Directions• BearingsBearings are

compass directions, which are used to obtain the precise directions of one place or feature with another.

• They are measured in degrees in a clockwise directionclockwise direction from the northnorth.

How to Determine Directions using

Bearings?

1) To measure the bearing of B from A, draw a straight line straight line joining the two points. joining the two points.

2) Draw a line parallel to the line parallel to the Grid NorthGrid North through A.

3) Place the centre of the protractor over A, with the 0° on the protractor pointing to the North.

4) Read the bearing off the protractor where the line AB cuts the outer edge of the protractor.

A

B N

131°

A

B

N

The bearing of B from A is 100°

A

C

Let’s Practice how to read bearings

N

The bearing of C from A is 180° + 50° = 230°

What happens if I want to drive or take a bus to my destination?

How do I find out what is the distance between the two points?

So that I can estimate how much time I need to get there?

Measuring distances• Scale: ratio of

a distance on a map to the actual distance on the Earth’s surface.

Representing a Scale on a Representing a Scale on a mapmap

1)1) As a statement in words As a statement in words • For example, 1 centimetre represents 1

kilometre. • This means that 1 centimetre on a map

represents 1 kilometre on the Earth’s surface.

• Therefore, if the distance of a road measured on a map is 9 centimetres, the actual distance of the road is 9 kilometres.

Representing a Scale on a Representing a Scale on a mapmap

2) As a representative fraction 2) As a representative fraction (R.F.)(R.F.)

• This is expressed as a ratio or fraction, for example, 1:25 000 or 1/ 25 000 may mean 1 milimetre represents 25 000 milimetres or 1 centimetre represents 25 000 centimetres and so on.

• Distances can be easily calculated using the R.F. For example, if the distance of a HDB flat from a bus stop is 2 centimetres on a map (1 centimetre represents 25 000 centimetres), then the actual distance is = 2 X 25 000 centimetres = 50 000 centimetres or 0.5 kilometres

Representing a Scale on a Representing a Scale on a mapmap

3)3) As a line or linear scaleAs a line or linear scale• A linear scale consists of a line that is

divided into units and sub-units such that measurements can be read off easily and accurately.

• A linear scale can be easily converted into a scale using a statement or a R.F.

• For example, in the diagram below, a distance of 1 kilometre on the linear scale measures 2 centimetres. This means that 2 centimetres represent 1 kilometres or 1 centimetre represents 0.5 kilometres. Metres 1000 0 1 2 3 kilometres

A linear scale

B) Reading Topographical maps

4) Scales (Large Scale/ Small Scale)

4) Scales (Large Scale/ Small Scale)

Measuring distancesMeasuring distances1. Ruler

2. Pen

3. String

4. Piece of paper

How the height of the mountain I am

climbing?

How do I find out how

steep is the road I am going on?

Representing heights

• Spot height– indicates the specific height of a point on a map. – Spot heights are not marked on the ground –

they are found only on maps, represented by the a symbol ( ), with its height written next to it.

• Bench mark– Surveyor’s mark cut in some durable material

such as a rock or a building. – It indicates the height of a place above sea level. – A bench mark is represented by a symbol. ( ←)

• A trigonometrical point, is a circular metallic disc placed in the ground to show that specific height.

• It is represented on a ma by a symbol shown by a small triangle or a circle with a black dot inside, represents a concrete pillar called a trigonometrical station.

• The height of a trigonometrical station is very accurately calculated above mean sea level. This height is printed alongside the trigonometrical point on the map.

• Trigonometrical stations are usually found on hilltops and mountain peaks.

426

2546

3281

Representing heights

• Gradient refers to the slope of a feature, such as a road, railway, or river.

• A gradient may be written as an angle or as an ratio between the vertical rise in a given horizontal distance.

Representing heights

Calculating gradient