Geographical Positions

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

The First Maps

This is a map, dating from 1513, which was made by a man named Piri Ibn Haji Memmed, otherwise known as Piri Re'is. This man was an Admiral in the Turkish navy. Today we only have a fragment of the original map.

Piri Rei’s Claim

Piri Re'is made a number of very interesting claims about this map:

•He claimed it was made from approximately 20 original source maps. •He claimed the western portion of the map was obtained from Christopher Columbus •He claimed some of the source maps were dated from the time of Alexander the Great. •He claimed some of the maps were based upon mathematics.

Different Types of maps

Dot Density: The features of a polygon theme are displayed with a number of dots corresponding to a value. This method is good for showing how particular things are distributed throughout an area. For instance, a dot map depicting population will most likely have the strongest concentrations of dots along rivers and near coastlines.

Different Types of maps

Planimetric maps are simple maps that do not attempt to show the relief features in measurable form. They may be base maps with shorelines and boundaries, plus certain basic geographic features such as rivers, roads, administrative zones, and other information. Or they can be cadastral maps with the location of property-ownership lines.

Different Types of maps

Topographic maps are maps that show the shape and elevation of terrain. They have many uses, such as designing gardens and parks, building roads and pipes, planing hiking routes, and so on. Flood control maps and engineering maps (sometimes called plans) are examples of topographic maps.

Different Types of maps

Remotely sensed images are geographic information gathered by means of a sensor. The common remote sensing images include aerial photographs, radar images, and satellite images. These images are important sources for producing digital maps and are useful for monitoring environmental changes and human activities.

Singapore map

Names of Features

Scale

Symbols andLegends

DirectionalIndicator

Grid Lines

Title

Names of Features

Scale

Names of Features

Scale

Next

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

Back

Name of Features

• Features include:– Roads– Settlements– Rivers

• Naming them helps us to identify these features.

Back

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.

Back

Grid Lines

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

• They are used to locate features on a map.

Back

Directional Indicator

• It show where – North– South – East– West lies

North (Never)

East (Eat)

South (Sour)

West (Watermelon)

Back

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.

Back

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

• Latitude (parallels)– Imaginary horizontal lines running in an east-west

direction around the world– Numbered from 0 to 90°N and 90°S

Finding Location (cont)

• Longitude (meridians)– Imaginary lines that run in a north-south

direction from North Pole to South Pole– Numbered from 0° at Greenwich to 180°E

and 180°W– Longitude 180°E and 180°W are the same

line.

Finding Location

• Latitudes and Longitudes– Latitudes and longitudes are imaginary lines which

cannot be seen on the actual surface of the Earth– Expressed as degrees of a circle measured from

the centre of the Earth– Measured in degrees(°), minutes(‘) and seconds(“)– 1° = 60’– 1’ = 60”– Latitude is always read 1st before longitude.

• Eg. Singapore is located at 1°17’N 103°51’E

Use of Latitude and Longitude

30°N 10°E

Finding location using a grid reference

• There are basically 2 types of grid references– Four figure grid references– Six figure grid references

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.

Finding direction using cardinal points.

• Find the direction of X from Y– Draw a line joining the two places or

feature– At X, Draw a vertical line that is parallel to

the eastings of the map. This line indicates North

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

Bearings

• 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.

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.

Contour Patterns and Physical Features

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

Contour Patterns and Physical Features(cont)

• A ridge is a linear or elongated upland area.

Contour Patterns and Physical Features(cont)

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

Contour Patterns and Physical Features(cont)

• 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