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1CRAWFORD COLLEGE LONEHILL GEOGRAPHY

AS LONG AS PEOPLE HAVE BEEN LITERATE, THEY HAVE USED MAPS.


MAPS HAVE BEEN USED FOR CENTURIES AS A RECORD OF KNOWLEDGE AND AS A MEANS TO EXPRESS THAT KNOWLEDGE


TODAY, MORE THAN EVER BEFORE, PEOPLE ARE USING MAPS.

THEY USE MAPS TO EXPRESS, ANALYSE AND UNDERSTAND KNOWLEDGE AND INFORMATION


USING MAPS WE CAN VISUALISE RELATIONSHIPS AND CONNECTIONS BETWEEN THINGS IN A WAY WE CANNOT DO WITH ANYTHING ELSE.

ALMOST EVERY GRAPH, TABLE OR OTHER GRAPHICAL REPRESENTATION CAN BE BETTER REPRESENTED WITH A CUSTOMISED MAP.


THERE IS A MAP FOR ALMOST ANYTHING YOU CAN THINK OF AND THEY ARE GENERALLY ARRANGED INTO THREE CATEGORIES:


POLITICAL MAPS


Topographical maps These show physical and human features of the land. Includes natural landscape features like coastlines, mountains, rivers, forest etc and features associated with human activity like dams, agriculture, cities, roads, railway lines etc. Special map symbols are used to represent these features.Small land surfaces are shown in great detail.


Thematic Maps…


What is a map? A map is a reduced, generalised, symbolic representation of a curved portion of theearth's surface on a piece of paper.

All maps must have: a scale direction of True North a key with the symbols used.

Maps are constructed from aerial photographs.


WHAT DIFFERENT THINGS DO WE FIND ON AND AROUND A TOPOGRAPHICAL MAP?


LATITUD

E M

ARKING

S

NATURAL FEATURES

MAP

NAM

E AN

D CO

DE

LON

GITU

DE

MARKIN

GS

MAN MADE FEATURES

RATIO SCALE

KEY

CONTOUR LINES


CONTOUR INTERVAL

MAP-CODE GRID

NORTH ARROW AND DECLINATION

INFO

LINE SCALE

PUBLICATION DETAILS AND

DATEPROJECTION

INFO


PROJECTION

GRID

PS: A TRIG BEACON (IN CASE YOU’VE EVER WONDERED)


Oblique photographs These are taken from an aeroplane or high point at an angle.They can tell the viewer a great deal about the nature of features, particularly heights but are only of limited use to the cartographer because decreasing scale

from foreground to background makes measurements of distances almost impossible.

Advantages: Disadvantages:

If the horizon is visible, the photograph is called a ................. oblique photograph

- it is taken at an angle of between 60 to 90 from the horizon.

A .................... oblique does not show the horizon and is taken at an angle of ..........


High angle

Low angle


Vertical Aerial photographs These are taken from an aeroplane where the camera points down vertically i.e. a ............. anglefrom the horizon.Most objects can be seen although tall trees might hide smaller objects, no building obscures otherbuildings.The area of buildings can be accurately judged and the layout of the roads and

railways is clearly shown.Tall trees, chimneys etc. can be recognised by their shadow.

Advantages:

Disadvantages: How are Vertical Aerial photographs taken? Cameras are installed in an aircraft which flies over an area in parallel strips taking photographs at regular intervals.There is an overlap of ....... % between successive photographs in a flight strip and a......... % overlap between adjacent flight strips.


Satellite Photographs These are the photographs of the future.Information is gathered by a satellite which has been launched into space and this information

is sent back to earth.

The type of information collected can be used to forecast weather, detect rocks which contain valuable minerals and the images can be used to draw accurate maps of areas.


Orthophoto maps These are a combination of vertical aerial photographs and topographic maps.

The scale of an orthophoto map is 1: 10 000, which means that they are largescale, and show a close-up, detailed view.

Advantages:

They combine the advantages of vertical aerial photographs with maps.


Place names

Contour lines, trig beacons, bench marks and spot

height


They can also be used with maps to

provide more detail


Photo scale = (PD / MD) x MS


There are THREE types of map based on scale:

Small-scale Maps (Smaller than 1: 5 000 000)•These are used to show patterns of continental and world extent e.g. distribution of land and water surfaces, railways of Africa etc.•These maps are generalised i.e. main roads, rivers, large towns and cities.•A world map or map of Southern Africa is a small-scale map.

Medium-scale Maps (Between 1: 5 000 000 to 1: 500 000)•These maps are used for data on a national and regional basis.•Roads, maps of drainage systems and administrative boundaries are shown.•A map of South Africa showing the provinces, towns and transport networks is an example of a medium-scale map.

Large-scale Maps (Larger than 1: 500 000)•These maps give detailed information.•Land forms, agricultural land use, streets in towns and distribution of farms shown.•These include the 1: 50 000 topographical maps and 1: 10 000 orthophoto maps used by geographers.


Using Map Scales•A map scale is the relationship between a distance depicted on a map and the corresponding distance in reality (on the ground.) •There are THREE types of scales:

Numerical Scales•These are representative fractions or ratios e.g. 1: 50 000•This means that 1 unit on the map represents 50 000 of the same units on the ground.

Verbal or Word Scales•A comparison is made e.g. mm to km cm to m.• EXAMPLE1: 50 0001 mm on the map represents 50 000 mm on the groundK H D M d c m0 0 5 0,0 0 0therefore 1 mm on the map represents 50 m on the ground.1 cm on the map represents 0,25 km on the ground.K H D M d c m •2 5 0 0 0, 0therefore 1 cm on the map represents 25 000 cm on the ground.Numerical ratio is 1: 25 000.

Linear Scales•This is a horizontal straight line on which distances are shown in terms of their equivalent on the map.•They are useful to measure the approximate distance between points.


CALCULATING STRAIGHT LINE AND WINDING DISTANCES

Formula: MAP DISTANCE SCALE

Method:Find the distance on the map in centimetres. If it’s a winding distance, use a piece of string, a piece of paper, or dividers to measure the distance (see diagrams A and B.) Use a ruler to measure straight lines.

Example: MD = 25 cmSCALE = 1: 50 000(Calculate the distance in Kilometers) = 25 cm x 0,5 km (MD x SCALE)= 12, 5 km

1: 50 000 SHORTCUTS ?


CALCULATING AREA Formula: (LENGTH SCALE) (BREADTH SCALE)

or, (L S) (B S)

Example: Work out the area of A.

A = (L x S) (B x S)

= (8 x 0,5 km) (4 x 0,5 km)

= (4 km) (2 km)

= 8 km2

( Scale = 1: 50 000 )

A

8 cm

4 cm


Direction This indicated by the points ona compass e.g. North, South, North-east etc.



REMEMBER TO START AT ‘FROM’ POINT

True and Magnetic bearings •A true bearing is measured in degrees from true north in a clockwise direction.•To measure true north, the points must be joined with a straight line.•A vertical line is then drawn through the point from which the bearing is to be measured.•This line represents true north and is drawn parallel to the lines of longitude.•The protractor is placed with 0/360° at the top and 180° at the bottom.•The measurement is read clockwise from true north to the line joining the two points.

True Bearings A true, geographic or azimuthal bearing is represented by an angle measured with a protractor.

Method: Join up the two points with a straight line. Draw a perpendicular line through each of the points, parallel to the lines of longitude. Measure the bearing with a protractor at the point where the questions reads FROM. Measure CLOCKWISE from the perpendicular line (True North) to the line joining the

two points. 0/360 on the protractor should be at the top. Read the bearing on the outer ring of the

protractor. The answer will be in degrees()


180

+20

= 200


•A magnetic bearing is read from a magnetic compass and includes the true bearing and

the magnetic declination.•This is because a compass needle always points to Magnetic North, and not the

geographic North Pole (True North).•The earth is like a big magnet with one pole in the Arctic region and the other pole in the

Antarctic region.•These magnetic poles change their positions very slowly.•The angle between the direction in which the compass needle points and True North

is known as the magnetic declination.•This is measured in degrees East or West of True North, and depends on the position of

the point in relation to the True and Magnetic North. Refer to the diagram below.


3) POSITION (LATITUDE AND LONGITUDE)

Co-ordinates are used to locate features on a map. They consist of a LATITUDE and a LONGITUDE reading. Lines of latitude and lines of longitude are imaginary lines running from east to west and north to south respectively. Where any lines of latitude and longitude intersect, a co-ordinate is read.

Latitude readings are given as either north or south (of the Equator), and lines of longitude are given as either east or west (of the Greenwich Meridian).

Co-ordinates always have the latitude reading first, and the longitude reading last.

The distance between lines of latitude are always 37mm, but the distance between the lines of longitude might vary.


How are co-ordinates used to fix positions? The absolute location of any point on the Earth's surface can be indicated

byusing geographical co-ordinates.Geographical co-ordinates refer to the lines of latitude and longitude.A line of latitude is an imaginary circle running around the globe parallel to

the equator. Degrees of latitude are the angular distance measured at the centre of the

earth.Lines of latitude are also called parallels. There are 180 of latitude.The equator at 0 is the most important.A line of longitude is an imaginary line joining the North and South poles.A degree of longitude is the angular distance measured at the centre of the earth.Lines of longitude are also called meridians.There are 180 of longitude - 0 or Greenwich meridian is the most

important.The degree of Latitude is given first, followed by the degree of longitude –

read DOWN first and then RIGHT.Each degree of latitude and longitude is divided into 60 minutes (') and

eachminute into 10 units or 30 seconds (“). Please note that seconds are not

used inthe Gauteng Matric exam.


DOWN, THEN RIGHT

1 MINUTE OF LATITUDE

10 DECIMALS IN EACH MINUTE

33°45’, 8 SOUTH

19°18’, 3 EAST


How are 1:10 000 Orthophoto map reference different?

An orthophoto map with a larger scale of 1:10 000 covers a smaller area than a topographical map.One topographical map sheet contains 25 orthophoto map sheets.E.g.: 2334 AD 12


THE THIRD DIMENSION



SP

UR

VA

LLEY

V

LANDFORMS


LANDFORMS

CONVEXS

PU

R

VA

LLEY

V

CONCAVE GENTLE

STEEP

SADDLE

POORT / GAP

TERRACED SLOPE

CRAWFORD COLLEGE LONEHILL GEOGRAPHY 57

The Spacing of Contour Lines: Different Slope Types Concave Slopes The lines are far apart at the bottom of the slope (gentle), but close together at the top (steep). It forms a hollowed out shape in a cross-section. Convex Slopes The opposite to a concave slope. The lines are far apart at the top of the slope( gentle) and close together at the bottom (steep). The slope forms a bulge in cross-section. Terraced or Stepped Slopes The contour lines are alternatively spaced far apart and close together. These slopes are common in the Karoo and Free State where different layers of hard and soft rock produce a stepped slope. Cliffs The contour lines touch or are very close together producing a vertical or near vertical rise of land.


How are landforms recognised by contour patterns? Valleys and Spurs Contour lines both form a "V" shape - in a valley the point of the "V" faces upstream, and a valley often contains a river.The point of the "V" in a spur faces downhill.A spur is a ridge from a range of hills or mountains.They often have convex slopes and occur between two valleys.They form local watersheds and direct rainfall into the surrounding valleys.They never contain a river. Gorge A deeply incised river valley - it is very narrow with steep sides e.g. Oribi Gorge. Waterfalls These occur in a river valley where the contour lines touch to form a cliff.The water flows over the cliff producing a waterfall e.g. Howick Falls. Watershed or Divide The boundary between drainage areas is called the watershed.It is drawn as a dotted line along the high points and crests of spurs.A watershed normally bisects spurs and high points e.g. hills, mountain ridges etc.It separates water flowing in opposite directions e.g. The Witwatersrand.

Scarp and Dip slope A scarp is an area where the contour lines are close together producing a steep rise (Cliff).The large form of this feature is called an EscarpmentA Dip slope often occurs in conjunction with a scarp slope.It is a gentle slope that slopes away from the top of the scarp.

Saddle A gentle dip that occurs between two hilltops or mountain peaks.It is seldom more than two contours in depth.

Pass or Neck A large dip in a range of hills or mountains.It is at a higher elevation than the surrounding plain.It often contains roads or railway lines.A "V" shape can be seen increasing in altitude jutting out from either side of the pass e.g. Van Reenen's Pass.

Poort or Gap A river cuts through a range of hills or mountains.This forms a break in the range at the same elevation as the surrounding plain.Roads and railway lines also go through poorts.The contour lines do not form a "V" shape in the poort e.g. Hartebeespoort in the Magaliesberg and Meiring's Poort in the Swartberg.


What is Gradient and how is it calculated?

The slope of the land is called the GRADIENT.In South Africa, main railway lines have a gradient of less than 1: 50 with a maximum of 1: 66. National roads have gradients of approximately 1: 20

A 1:1 gradient is very steep and can only be climbed by using feet and hands.

Formula:

Gradient = Rise or Vertical distance or Difference in heightRun Horizontal distance Distance on ground



CROSS-SECTIONS

Mark-off

Infer / deduce

Study

Graph

Label


VERTICAL EXAGGERATION

How is the vertical exaggeration of a cross-section worked out? All cross-sections are drawn to a particular vertical scale and if we change the scale, we can also change the appearance of the cross-section.

Formula V.E = VS or Vertical Scale HS Horizontal Scale

Method Write down the formula.Substitute the information given to you into the formula.Change the VS from a word scale to a numerical scale (a ratio).Write both ratios as representative fractions.Invert the bottom fraction and multiply out.Divide the numerator (top number) by the denominator (bottom number)The answer will be x times


What do we mean by inter-visibility? This is to determine whether one point can be seen from another point on the cross-section.Once the cross-section is drawn, join the two points you are trying to establish the intervisibility of with a line.If there is no obstruction, there is intervisibility between the two points.If there is topography obstructing the line of sight, then there is no intervisibility



INTERPRETING MAPS

CONSIDER THE FOLLOWING SENTENCE:

A turgle swashed a brad while it snorped an urple troxle.

You should be able to READ this sentence quite easily, even though you may have no idea what it means. You can even ANALYSE it relatively easily. For example, you can count the words, or the words with four letters or more…you should even be able to work out which are the nouns and verbs.

INTERPRETING the sentence though, requires a little more. In interpreting anything, including the strange sentence above, it is important that you find MEANING and valuable conclusions about what you are analyzing. But to do this, you need EVIDENCE. You simply do not have enough evidence to interpret the example

If someone told you that ‘troxles’ are plants. What would brads be?

It is important, when you try to interpret anything that you LOOK FOR EVIDENCE FIRST!

This is especially true when interpreting maps.


MAP PROJECTIONS

What is a Map Projection? Map projections are a system for transferring the surface of the spherical Earth to a flat area. In order to do this the continuity of the map is broken e.g. the globe gores map and/or certain spherical properties are sacrificed, creating deformation and/or distortion in:Direction and bearingShape/angles at different pointsAreaDistances

No map can accurately show all these factors, so depending on the purpose of the map, certain factors are more or less important and therefore the projection chosen depends on the purpose for which the map will be used e.g. for a pilot or sailor, direction and scale must be accurate. Different projections keep one or more properties true.


A map projection is an orderly system of lines of latitude (parallels) and lines of longitude (meridians) used as a basis for drawing a map on a flat surface. Azimuthal projections show correct direction/bearing relationshipsConformal projections are true in terms of shape/form for small areasEqual-area projections show correct area relationshipsMaps that correctly show the distance between points are often called equidistant maps (note that the shortest distance between two points on a map is generally not a straight line. but a curve).


Equal area projections preserve area, and are also called equivalent projections. Most thematic maps should use an equal area projection.

Conformal projections preserve angles, and are useful for navigational charts and weather maps. Lines of latitude and longitude intersect at right angles. Shape is preserved for small areas, but the shape of a large area such as a continent will be distorted significantly. Conformality is an extremely valuable property for maps that are to be used critically, and not just for general orientation or decoration. A common conformal projection is the Lambert Conformal Conic projection.

Equidistant projections preserve distances, but no projection can preserve distances from all points to all other points.

Azimuthal projections preserve direction from one point to all other points. This property can be combined with any of the other three. Thus, it is possible to have an equal area azimuthal projection, such as a Lambert Azimuthal Equal Area projection or an Azimuthal Equidistant projection.

Compromise projections attempt to minimize overall distortion, but preserve none of the four properties. The Robinson projection, for example, is neither equal area nor conformal, but is aesthetically pleasing and suitable for general mapping.


The 3 basic types of map projections are: 1.Cylindrical2.Conical3.Azimuthal



Azimuthal

Cylindrical

Conical

In Grade 11 you study Mercator’s cylindrical projection. This projection has equality of linear scale and therefore shows correct distance relationships.


Mathematical calculations are used to project lines of latitude and longitude onto a cylinder – visualize a paper cylinder wrapped around the globe with a light inside the cylinder projecting the graticule (lines of latitude and longitude) on it.

Parallels and meridians are straight lines and are parallel to one another.

Lines of latitude and longitude cross each other at right angles.

Distances between parallels become greater toward the poles in proportion to the distance between meridians.

The Mercator projection shows courses of constant bearing as straight lines. While common, scholars advise against using it for reference maps of the world because it drastically inflates the high latitudes.

10000 0 10000 20000 Miles

N

EW

S74CRAWFORD COLLEGE LONEHILL

GEOGRAPHY

What is GIS? It is a new tool that is used to make geography more relevant.It is a computer system that links geographic information (where things are) with descriptive information about those places (what thing are like)This info is used to produce new maps.The user selects what is required from many layers of different informatione.g. a map with roads, vegetation, where people live, rainfall amounts, peoples income, pollution etc.Geographic information is basic to biology, geology, environmental science, sociology, politics and economicsThe world’s problems exist in a geographic context and information can be used to predict, monitor and solve these problems.


Terminology Entity: A real world feature that can’t be subdivided e.g. a tree, house, river etc. Attribute: A quality or characteristic. Object: A point or set of points used to represent a real world entity. There are three types of objects: Point: A GIS object that represents a geographical feature that is too small to show as a line or area on a small scale map e.g. lamp post or post box. These are defined by their co-ordinates. Point Line: A set of ordered co-ordinates that represent a narrow one-dimensional geographical feature such as a stream or road. The beginning and end points called nodes.

(node)

Line Curved Line Directed Line Intersecting Line

Area: A two-dimensional object such as a recreational area or dam. The boundaries of the area are defined by a closed set of lines called a polygon.



Terminology VECTOR DATA: POINTS AND LINES RASTER DATA: ‘PIXEL’ OR SHADED DATA (SCANNED MAPS

AND PHOTOS) DATA MANAGEMENT

Storage requirements, cross-referencing, analysing and ease of access (vector data often preferred).


INFORMATION IS ACQUIRED VIA REMOTE SENSING, GEO-REFERENCED TABULAR DATA AND FIELDWORK

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