UNDERSTANDING MAPS

Geographical Data Skills (Part 1)

What are maps?◦Maps are pictures or graphical representations of all or a part of the Earth’s surface and its features.

◦ Examples of maps:◦ Atlas

◦ World map

◦ Street directory

◦ Dot maps

◦ Isobars, Isotherms, contour maps, etc

Functions of Maps

◦Different types of maps would represent different data variables, or perspectives of the map-maker.

◦ For example, all maps of the world will be distorted to a certain degree, depending on their intended use.

Functions of Maps

Standard World Map (Mercator Projection)

Functions of Maps

Peters Projection

Different Types of maps

Dot Density mapsThe features of a polygon

theme are displayed with a number of dots corresponding to a value.

Used for:Showing how particular things

are distributed throughout an area

Different Types of maps

Topographic maps Shows the shape and elevation of terrain.

Used for: To understand the earth’s terrainTo plan routes and buildingsTo establish evacuation routes and flood control maps. For hazard mapping.

Different Types of maps

Remotely sensed images Geographic information gathered by means of a sensor. The common remote sensing images include aerial photographs, radar images, and satellite images.

Used for: These images are important sources for producing digital maps and are useful for monitoring environmental changes and human activities.

Names of Features

Scale

Symbols andLegends

DirectionalIndicator

Grid Lines

TitleNames of Features

Scale

Names of Features

Scale

Key Parts of a Map

Title◦ The title of the map states what the map shows

◦ It usually appears on top of the map

◦On topographical maps, the title is usually the name of the largest settlement on the map

Name of Features

◦ Features include:◦ Roads◦ Settlements◦ Rivers

◦Naming them helps us to identify these features.

Scale

◦ The scale shows the size of the map as compared to the actual size of the area that the map represents.

◦ Purpose:◦ Allows the user to calculate exactly how big or small a features is on

the earth’s surface.

Grid Lines

◦Grid lines are a series of numbered vertical lines drawn on a map.

◦ They are used to locate features on a map.

Directional Indicator

◦ It shows where ◦ North◦ South ◦ East◦ West lies

North (Never)

East (Eat)

South (Sour)

West (Watermelon)

Symbols and Legends

◦ Symbols are used to represent the different physical or man-made features found on the surface of the Earth.

◦ Symbols are used because it is possible to fit a lot of information into a small space.

◦ Legend lists all the symbols used in the map and explains what each of them mean or represent.

READING TOPOGRAPHICA

L MAPS

Measuring Distance

◦ A scale can be shown on a map in 3 ways:◦ As a statement

◦ As a representative or fraction

◦ As a line or linear scale

1 cm represents 2 km

1:200000

Measuring Distance (cont)

◦Measuring a straight line:◦ Use a ruler to measure the length between two points.◦ Use the scale of the map to find out the actual distance on the

ground.◦ Eg if the scale of the map is 1:10000, then a length of 1cm on the map is

equivalent to 10000cm(0.1km / 100 metres)

Measuring Distance (cont)

◦Measuring distance along a curve◦Place one end of the string at the starting point. Hold

this end down firmly with your finger.◦Use the string to follow the path with your fingers

slowly.◦When you reach the end, use a pencil to mark the

string.◦Remove the string and measure the distance against a

ruler.◦Use the scale to convert the length to actual distance

on the ground.

Finding Location

Atlas/World Maps Topographical Maps

Longitudes/Latitudes Grid references

Locations in a topographic map can be found using grid references.

◦There are basically 2 types of grid references◦Four figure grid references◦Six figure grid references

Finding Location (Topo Map)

1391

Finding Direction

◦ Cardinal Points are points marked on a compass.

◦ Besides the basic North, South, East, West, there are additional points marked North East, South East, South West, North West. N

SW SE

NE

W E

S

NW

Finding direction using cardinal points.

◦Find the direction of X from Y◦Draw a line joining the

two places or feature◦Draw a mini vertical and

horizontal line, which intersects at X

◦ Look at X and use one of the cardinal points to describe the position of Y from X.

Bearings (Angles!)◦Measure the bearing of B from A

◦ Draw a line to join the two points◦ Place the protractor at A. The 0° on the protractor must point to

North◦ The point on the outer edge of the protractor where the line joining

A and B crosses show the bearing of B from point A.

QUICK ACTIVITY!

Pg 23 of your Geography workbook

Q1 – 5

CONTOURS

Using Contours to represent relief◦ A contour is an imaginary line joining places of the same

height above sea level

◦ Besides showing us the height, contours also tell us about the ◦ Shape◦ Slope

Using Contours to represent relief◦ Some points to remember about contours:

◦ Contour lines that are close together denote steep slopes.◦ Contour lines that are far apart indicate gentle slopes.◦ When there are no contours, it means that the land is almost flat.

Contours joined in a circular form, with contour lines increasing in height towards the centre can indicate a hill or a mountain.

◦ A ridge is a linear or elongated upland area.

◦ A plateau is similar to a ridge but it has a steep slope and flat summit.

◦ A valley’s contours point towards higher ground forming an inverted ‘V’

Gradient

◦ The gradient of a feature refers to the steepness of the slope of that feature.

◦Usually expressed as a ratio between vertical distance risen in relation to horizontal distance covered.

Gradient =Vertical Distance

Horizontal Distance

Horizontal Distance

GradientOf AB =

Vertical Distance

=20 m

10000 m

=1

5001:500

Both values in same units,Make numerator 1

Drawing a cross-section◦Draw a line joining the two points

◦On a sheet of paper, draw 2 axes

◦Label the height of the contour on the y-axis

◦Place the piece of paper below and from the left, drop a perpendicular line from where each contour line cuts its corresponding height

◦Draw horizontal lines for all contour

◦ Join the points together to make a smooth and even outline