Cartographic skills (Cambridge (CIE) IGCSE Geography): Revision Note

Maps

• Questions in the exam will be based on topographical maps 

  • The maps can be from anywhere in the world

  • Maps will have a key, scale, northings and eastings

  • These all need to be used to answer the questions

Grid references

Grid references

• 4-figure are used to locate specific grid squares within the map

  • The first two figures are the eastings, which indicate how far east or west a grid is across the map

  • The second two figures are the northings, which indicate how far north or south a grid is on the map

• 6-figure grid references are used to locate exact points within grid squares

  • The first three figures are the eastings 

  • The second three figures are the northings

• To find a 4- and 6 figure grid reference

  • To find the four-figure grid reference, give the number from the bottom of the map first, then the number from the side 

• In image above, the 4-figure grid reference would be 17, 51

• To give the 6-figure grid reference, you need to imagine that the grid square is divided into 100 smaller squares 

Scale

• Maps in exams will be scaled at either:

  • 1:25,000 (1 cm = 250 m in real life)

  • 1:50,000 (1 cm = 500 m in real life)

• Distance measurement methods:

  • For straight or nearly straight distances:

    • Use a ruler

    • Use the edge of a straight piece of paper

  • Using map scale:

    • Mark distances on a piece of paper using the scale at the map's bottom

    • Lay the marked paper from first to second point to calculate distance

• Measuring curved route distances:

  • Divide the route into segments

  • Rotate and mark the paper in stages to calculate the full distance

• Measuring road routes on the map:

  • Divide the route into straight sections using crosses

  • Use the paper to measure from A to the first cross

  • Rotate the paper, pivoting at the cross to mark the second cross

Area

• The scale of a map is important when accurately calculating area

• Areas can be divided into squares and triangles to make the calculation easier

  • The area of a rectangle = length x width

  • The area of a triangle = 1/2 base x height

• For a map with the scale 1:25,000

• To calculate an area where the length on the map is 4 cm and the width is 2 cm, the calculation is as follows:

  • Length 4 x 25,000 = 100,000 = 1,000 metres

  • Width 2 x 25,000 = 50,000 = 500 meters

• Area in m² = 1000 x 500 = 500,000 meters² or 0.5km²

Bearings

• Directions on a map should always be given using compass points

• There are 16 compass points 

• A grid bearing is measured from the grid north at 0°, east at 90°, south at 180°, and west at 270°

• Grid bearings are given using a protractor

  • The 0^º should be pointing north and the centre of the protractor should be on the place the bearing is been given from

  • The compass direction and grid bearing from the crossroads at A to the location at B

• On the map below, B is south-west of A 

• The bearing is 280^º

Height

• There are three ways to display height:

  • spot height

  • contour lines

  • trigonometrical (trig) stations

• Spot heights show the height at a specific point with the height measurement written next to it

• Contour lines are isolines

  • They join points of equal height and are usually at 5 or 10-metre intervals (distance between the contour line)

  • This means that the height of the land increases by 5 or 10 metres between the lines

• A trigonometrical (trig) station is marked by a small black triangle with a height measurement written next to it

Topography

• The contour lines can also indicate the shape and slope of the land or topography

• Contour lines close together indicate steep land

• Contour lines very far apart indicate gently sloping or flat land, dependent on the distance apart

• V-shaped valleys have a v-shaped set of contours 

• A hill is shown by a set of circular contour lines

Cross-sections

• A cross-section is a slice through the landscape

• They are represented on a map by a line, which is often labelled A at one end and B at the other

• They use the contour lines to determine the height of the land

• A piece of paper is then laid along the line and points A and B are marked on

• The contour lines are then marked on each time they cross the paper

• These figures can then be used to create the cross-section 

Key

• Maps can be used to identify a range of landscape features

• These may be physical and human features

• Each map has a key to show what the symbols mean