Maps and Map Work - Geography Form 1 Notes

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Definition

- Map - representation of the whole or part of the earth’s surface drawn to scale.

  • Shows outline of objects on the ground
  • Drawn as if the drawer was above the ground
  • It shows details
  • Most of the features are indicated by symbols.

- Picture: image of a real object.

  • Gives details in their visible shapes and sizes
  • Can be inform of free hand, drawing, painting or a photograph
  • Not drawn to scale

- Plan: outline of something drawn to scale.

  • Also drawn as if a person was directly above the ground
  • It represents a very small place
  • The scale is large to show details e.g. house plan
  • Gives specific information


Types of Maps

  • Classified according to the purpose for which each map is drawn.
    • Topographical Maps: This shows selected natural physical features on a small portion of a country.
    • Atlas maps: this is a collection of maps in one volume.
    • Sketch maps: maps which are roughly drawn. A good sketch map should have the following characteristics:
      1. neat and clear
      2. title
      3. frame
      4. key
      5. compass direction


Uses of Maps

  1. Sketch maps are used to summarise information for easy reference.
  2. Used for locating other countries.
  3. Used for comparing sizes of countries.
  4. For locating climatic regions of different parts of the world.
  5. Give information on distribution of geographical phenomena e.g. vegetation on the earth’s surface.
  6. Help travellers to find their way.
  7. Used to calculate distance of a certain place.
  8. Used to locate physical features like landforms.


Marginal Information

- Information contained in the area surrounding the map.

  1. Map name e.g. Yimbo.
  2. Sheet title e.g. East Africa 1:50000 (Kenya).
  3. grid system numbers
  4. latitudes and longitudes
  5. Compass direction with grid, true and magnetic north.
  6. scales
  7. key
  8. publisher and copyright
  9. Map identification
    • Map series
    • Sheet number or sheet index
    • Sizes of Scales


Map Scales

  • A scale is a ratio of a distance on a map to a corresponding distance on the ground.

Types of Scales

  • Statement scale –expressed in words e.g. 1cm represents 1km, 1cm to 1km.
  • Representative Fraction (RF)-expressed as a fraction or ratio e.g. 1/200,000 or 1:200,000.
  • Linear scale-shown by a line which is subdivided into smaller units.

Conversion of Scales

Statement Scale into RF

1cm rep 1km to RF

  • Multiply the number of kilometres by 100,000 (1km=100,000cm) i.e. 1×100000=100,000.
  • Statement scale is 1/100,000 or 1:100,000.

2cm rep 1km

  • Divide both sides by two to get 1cm rep ½ kilometres.
  • Multiply ½ by 100,000 to get 50,000.
  • RF is 1/50,000 or 1:50,000.

RF to Statement Scale

  • Divide the denominator by 100,000.
  • Write the scale in statement form.

 

Linear Scale to Statement Scale

  • Measure a unit distance off a linear scale e.g.
    Linear scale to statement scale
  • The distance is 4-3=1km which is represented by 2cm.
  • Use the methods in (1) and (2) above.

    Q. Given that the ground distance is 200km while the distance on map is 20cm calculate the scale.

Sizes of Scales

  1. Small scales- show a large area of land on a small size of paper. They show limited details e.g. 1:250,000, 1:500,000, 1:1,000,000.
  2. Medium scales- used to represent a relatively smaller area on a given size of paper e.g. 1:50,000, 1:100,000, 1:125,000.
  3. Large scales-used to represent a small area of land on a given piece of paper. They show a lot of details e.g. 1:2,500, 1:10,000, 1:25000

Arranging Scales in Order

  • Ascending Order-smallest to largest
  • Descending Order-largest to smallest
    (1)1/500,000
    (3)1:25,000
    (4)1/10,000
    (2)1cm rep 500m

Uses of Scales

  1. Estimating distances on maps
  2. Measuring distances accurately-use dividers and ruler, piece of string or thread for curved distances or straight edge of paper.
    E.g. calculate actual distance of a line 8.5cm long on a map using the following scales.
    (i) 2cm rep 1km
    (ii) 1:100,000
  3. Calculation of areas-no. of full grid squares+ number of ½grid squares/2 or use of rectangles (l×b) or triangles (½ b×h).

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