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 maps The 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 terrain To plan routes and buildings To 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.

Key Parts of a Map Names of Features Names of Features Names of Title Grid Lines Scale Scale Scale Directional Indicator Symbols and Legends

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 topographical maps

Measuring Distance 1 cm represents 2 km 1:200000 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 Grid references Longitudes/Latitudes

Finding Location (Topo Map) 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

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Finding Direction N NW NE W E SW SE S 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 NW NE W E SW SE S

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 Gradient = Vertical Distance Horizontal Distance 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 Gradient Of AB = Vertical Distance 20 m 10000 m 1 500 1:500 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