MAPWORK
GRADE 10 - 12
MAPWORK
CONTENT:
GRADE 1012
The following topics will be studied
in mapwork:
• Mapwork skills (Locating exact
position, scale, direction, distance,
magnetic declination and bearing and
true bearing)
• 1:50 000 Topographical maps
• 1:10 000 Orthophoto maps
• Landforms and contours
• Simple cross sections
• Oblique and vertical aerial photograph
• Geographical Information Systems
(GIS)
GENERAL INFORMATION
GR 10 - 12
WHAT IS A MAP?
• A map is a symbolic representation of selected characteristics of a
place, usually drawn on a flat surface. Maps present information
about the world in a simple, visual way.
• They teach about the world by showing sizes and shapes of countries,
locations of features, and distances between places.
Topographic
map
Types of maps
Orthophoto
map
FEATURES ON A MAP:
NAME OF THE MAP:
The name of the map will always have the following information:
Name of the town
29
26
AA
BLOEMFONTEIN
This means that
Bloemfontein is in
quadrant A in block A.
A
C
A
C
A
C
B
A
D
C
B
A
D
C
B
B
D
B
D D
SCALE OF THE MAP:
• The scale of the map indicates the relationship between the actual
size of the area and the map that has been drawn of this area.
• There are THREE types of scales:
1. WORD SCALE:
3. LINE SCALE:
2. RATIO SCALE:
LARGE SCALE AND SMALL SCALE MAPS:
LARGE SCALE MAP:
Map that covers small areas and
show a lot of detail. Example: An
orthophoto map (1: 10 000)
SMALL SCALE MAP:
Map that covers a large area and
do not show much detail.
Example: A topographic map (1:
50 000)
DIRECTION:
• Direction is expressed by using the points of a compass (
North, East, South and West) and the points between them.
• There are 16 cardinal points:
KEY:
• A key is used to show conventional signs on a topographic map.
• Conventional signs are symbols for different features found on a map.
Three types of map symbols:
1. Line symbols: Represent lines on maps like roads, powerlines,
railway etc.
2. Point symbols: Represent point on maps like post office, police
station, buildings, shops etc.
3. Polygon/area symbols: Represent areas on maps like dams,
recreational parks, golf courses
HEIGHT ON MAPS:
Height on maps are indicated as follows:
Trigonometrical
station
Spot heights
Bench marks
ORTHOPHOTO MAP:
ORTHOPHOTO MAPS ARE MADE FROM AERIAL PHOTOGRAPHS.
TYPES OF AERIAL PHOTOGRAPHS:
1. Vertical aerial photographs:
• Photo is taken from an aeroplane which is flying directly over the
landscape;
• Photo is taken at a 90° angle;
• Shows the top view of the landscape;
• Has a bigger scale;
• Usually printed in black and white to save costs;
• Help to map large and inaccessible areas.
II. Oblique aerial photographs:
• Photographs that are taken from high above the ground at an
angle that is not vertical to the ground.
• Two types of oblique aerial photographs:
HIGH OBLIQUE PHOTO
LOW OBLIQUE PHOTO
Horizon is visible on the photo.
Horizon is not visible on the photo.
Shows a big area.
Shows a specific image of an area.
Images are distorted when landscape is far from
the lens.
Images are clear.
HOW ORTHOPHOTO MAPS ARE MADE:
• Orthophoto maps are made from aerial photographs.
• Map information like the names of streets and dams are added to the
orthophoto.
• Contour lines are superimposed on the photo to provide height of
the area or landscape;
• Orthophotos maps are therefore a combination of a photo and a
map;
• Digital mapping cameras are used where the camera is flown over an
area and the images are recorded and corrected according to scale;
• The scale of an orthophoto map is 1 : 10000, which means that 1
on the map represent 10 000 cm on the ground.
SHADOWS ON AN ORTHOPHOTO MAP:
• The direction of the shadow on an orthophoto map can determine
the time of the day the photo was taken.
• Always look for trees or buildings when determining the time of the
day.
• The longer the shadow the earlier it is (am) and the shorter the
shadow the later in the day it is.
• Shadows that lies to the SOUTHEAST means the photo are taken
after 12:00 NOT 12:00
• Shadows that lies to the SOUTHWEST means the photo are taken
before 12:00 NOT 12:00
FEATURES ON A TOPOGRAPHICAL MAP:
NATURAL FEATURES:
Any feature that appears naturally:
• Ocean, natural bays and shores;
• Islands
• Rivers, lakes and dams
• Bushes, vegetation and forests
Represented as blue areas (water resources) , brown lines (
contour lines) and green areas (natural vegetation like
bushes or forestry)
CONSTRUCTED (MAN MADE) FEATURES:
Any feature that is constructed on natural areas:
• Transport and infrastructures;
• Dam wall and dams;
• Cultivated land and purification
plants;
• Buildings and heritage sites.
Represented as black and grey lines,
grey areas, black symbols, green areas
that indicate cultivated lands, blue lines that indicate canals,
blue symbols and red lines.
INFORMATION FROM AERIAL PHOTOGRAPHS AND
MAPS:
The following information can be interpreted from photographs
and maps:
• The type of landform;
• The relief of the landform;
• Drainage patterns, drainage density and drainage distribution;
• Describe the settlement type: Urban or rural;
• Describe if the settlement is nucleated or dispersed;
• Describe the site and situation of a settlement;
• Indicate what the land is being used for.
MAP CALCULATIONS:
DISTANCE
GR 10 -12
Distance is the shortest distance between two point in a straight line.
Answer in km
Answer in m
Topographic map
x 0,5
x 500
Orthophoto map
x 0,1
x 100
Step 1: Measure the distance between the two points in
centimeter.
Step 2: Note the unit that the answer must be in. Make
use of the above table and the following formula:
Map distance = Distance x scale
EXAMPLE 1:
QUESTION: MEASURE THE DISTANCE BETWEEN THE SCHOOL AND
CHURCH IN KM.
Step 1 : Measure the straight line distance between the two points.
This is a
topographic
map.
ANSWER: 8,5 CM
Step 2: Use the table and the formula to determine the answer.
NOTE – The question asked for the distance in km.
Answer in km
Answer in m
Topographic map
x 0,5
x 500
Orthophoto map
x 0,1
x 100
Map distance = Distance x scale
Map distance = 8,5 cm x 0,5
Map distance = 4,25 km
EXAMPLE 2:
QUESTION: MEASURE THE DISTANCE BETWEEN spot height 1706
and spot height 1656 in m.
Step 1 : Measure the straight line distance between the two points.
This is an
orthophoto
map.
ANSWER: 7,4 CM
Step 2: Use the table and the formula to determine the answer.
NOTE – The question asked for the distance in m.
Answer in km
Answer in m
Topographic map
x 0,5
x 500
Orthophoto map
x 0,1
x 100
Map distance = Distance x scale
Map distance = 7,4 cm x 100
Map distance = 740 m
AREA
GR 11 & 12
The measurement of the size of a surface.
REMEMBER – WITH AREA YOU MUST MEASURE THEREFORE A SCALE MUST BE USED!!
METHOD 1: (Answer calculated in 𝒌𝒎𝟐 )
Measure the length and breadth separately… Assumed we worked on an
orthophoto map
Length = 8,5 cm
Now you have to multiply the measurement of length with the scale:
Answer in km
Answer in m
Topographic map
x 0,5
x 500
Orthophoto map
x 0,1
x 100
Length= Distance x scale
Length= 8,5 cm x 0,1
Length= 0,85 km
Now do the same for breadth:
Answer = 4,4 cm
Now you have to multiply the
measurement of breadth with the
scale:
Answer in km
Answer in m
Topographic map
x 0,5
x 500
Orthophoto map
x 0,1
x 100
Breadth= Distance x scale
Breadth = 4,4 cm x 0,1
Breadth = 0,44 km
Now write down the formula to calculate area:
A=𝒍 ×𝒃
Substitute the values calculated:
𝐴 = 0,85 𝑘𝑚 × 0,44 𝑘𝑚
𝐴 = 0,374 𝑘𝑚2
METHOD 2: (Answer calculated in 𝒌𝒎𝟐 )
We know from previous calculations that:
Length = 8,5 cm and Breadth = 4,4 cm
A=𝒍 ×𝒃
𝐴 = 8,5 × 0,1 × (4,4 × 0,1)
𝐴 = 0,85 𝑘𝑚 × 0,44 𝑘𝑚
𝐴 = 0,374 𝑘𝑚2
Area is
ALWAYS in
𝑘𝑚2 or 𝑚2
DIRECTION
GR 10 -12
DETERMINE DIRECTION:
Step 1: Join the two place with a line.
Step 2: Draw in the 8 main directions.
Step 3: Determine the direction.
EXAMPLE:
Determine the direction from trig beacon 153 to Bosrug.
As you can see on the map it is not one of the
directions drawn on the map, therefore it will be a
direction in-between the cardinal points.
(Refer to the diagram above)
Answer = WNW
BEARING
GR 10 -12
DETERMINE BEARING:
Step 1: Note from where the bearing must be measured.
Step 2: Draw a line between the two points.
Step 3: Place your protractor along the North – South line with the 0° at the
top.
Note the following:
If the point is
anywhere from 0° −
180° you just read
the degrees from the
outside of the
protractor.
If the point is
anywhere from
180° − 360° you
have to turn the
protractor around
and add the degrees
to 180°.
EXAMPLE 1:
QUESTION: Determine the Bearing from point A to point B:
Step 1: Join the two points with a straight line.
Step 2: Draw in the North to South and West to East line at the point you
must measure FROM.
Step 3 : Place your protractor along the North – South line with the 0° at the
top.
Now read your answer
from the outer number.
Answer = 136°
EXAMPLE 2:
QUESTION: Determine the Bearing from point A to point C:
Step 1: Join the two points with a straight line.
Step 2: Draw in the North to South and West to East line at the point you
must measure FROM.
Step 3 : Place your protractor along the North – South line with the 0° at the
top.
Remember:
When you move past 180° you
must turn your protractor and
must add the reading on the
outer side to 180°.
Answer = 180° + 67° =247°
MAGNETIC
DECLINATION
GR 10-12
MAGNETIC DECLINATION:
• This is the angle between true north and the magnetic north.
• The magnetic declination changes yearly and must be calculated.
• This information can be found on the map.
• Magnetic declination can change in TWO direction:
 Westerly – The magnetic declination will INCREASE.
 Easterly – The magnetic declination will DECREASE.
Information on a map regarding the magnetic declination:
June 2011 refer to the month and year that the mean magnetic declination was
recorded.
June 2011 – May 2012 refers to the years that were used to calculate the mean
(average) magnetic declination. DO NOT USE THESE DATES IN
CALCULATIONS!
Mean annual change refers to how the magnetic declination changes each year.
HOW TO DETERMINE THE MAGNETIC DECLINATION:
QUESTION: Use the information on the map and determine the
magnetic declination for 2020.
STEP 1: Calculate the difference in years = Current year – Year on the map
Difference in years = 2020 – 2011
Difference in years = 9 years
STEP 2: State the mean annual change:
Mean annual change: 6’ W
STEP 3: Calculate the total change = difference in years x mean annual
change
Total change: 9 years x 6’ W
Total change: 54’ W
STEP 4: Add the total change to the magnetic declination for 2011
Magnetic declination for 2011: 26° 31’ W
Total change (2011 – 2020) : 54’ W
Magnetic declination = 26° 31’ + 00° 54” W
Press the following on your calculator:
Magnetic declination = 26
31
+ 00
Use your
calculator for
this
54
Magnetic declination = 27°25’ W (Remember the direction MUST be
indicated)
MAGNETIC
BEARING
GR 10-12
MAGNETIC BEARING:
QUESTION: Calculate the magnetic bearing of trig beacon 160 to
trig beacon 39.
Use the following formula: Magnetic bearing = True bearing +
Magnetic declination.
Step 1: Determine the bearing between the two points.
Answer = 110°
Step 2: Use the information on the map and determine the magnetic
declination.
1.
2.
3.
Difference in years = 2020 – 2011
Difference in years = 9 years
Total change: 9 years x 6’ W
Total change: 54’ W
Magnetic declination = 26° 31’ + 00° 54” W
Magnetic declination = 27°25’ W
Step 3: Use the answers and substitute it into the formula.
True bearing = 110°
Magnetic declination = 27°25’ W
Magnetic bearing = True bearing + Magnetic declination
Magnetic bearing = 110° + 27°25’W
Magnetic bearing = 137°25’
COORDINATES
GR 10 -12
POSITION/COORDINATES:
• Coordinates are a set of values that shows the exact location of a feature.
• Coordinates are given as degrees (°), minutes (‘) and seconds (“) and a
direction.
• Latitude and Longitude are used to give the exact position.
• In South Africa:
Latitude will ALWAYS be SOUTH therefore increase in minutes and
seconds when you move down on a map, and
Longitude will ALWAYS be EAST therefore increase when you move from
left to right on a map.
Remember:
60’ = 1°
60” = 1’
With the start of a new block it change
to the next minute.
QUESTION: DETERMINE THE COORDINATES OF TIG BEACON
345 IN BLOCK B1.
Note that the coordinates must be written in the following format:
00°00’00” S ; 00°00’00” E
Latitude
; Longitude
Step 1: Start with the latitude. Determine the degrees.
Answer: 33°
Step 2: Determine the minutes of the latitude.
Remember when moving from block A to block B 60 seconds has passed and
therefore it will be one minute more. The degrees remain the same.
Answer: 20’
Step 3: Now determine the seconds.
Use the following method:
1. Draw a line from the top to the point.
2. Measure the length of the line.
Answer: 2,4 cm
3. Now measure the length of the whole block B1.
Answer: 3,7 cm
4. Now do the following calculation to determine the seconds:
short line 60
Seconds =
×
long line
1
2,4 𝑐𝑚 60
𝑆𝑒𝑐𝑜𝑛𝑑𝑠 =
×
3,7 𝑐𝑚
1
Seconds = 38,9189
𝑆𝑒𝑐𝑜𝑛𝑑𝑠 ≈ 39“
5. Now write the whole value ( degrees, minutes, seconds and direction) of
the latitude:
33° 20’ 39” S
Step 4: Determine the degrees of the longitude
Answer: 25°
Step 5: Determine the minutes of the longitude.
Answer: 15’
Step 6: Now determine the seconds.
Use the following method:
1. Draw a line from the left to the point.
2. Measure the length of the line.
Answer = 3,1 cm
3. Now measure the width(breadth) of the whole block B1.
Answer = 4,2 cm
4. Now do the following calculation to determine the seconds:
short line 60
Seconds =
×
long line
1
3,1 𝑐𝑚 60
𝑆𝑒𝑐𝑜𝑛𝑑𝑠 =
×
4,2 𝑐𝑚
1
Seconds = 44, 2857
𝑆𝑒𝑐𝑜𝑛𝑑𝑠 ≈ 44“
5. Now write the whole value ( degrees, minutes, seconds and direction) of
the longitude:
25° 15’ 44” E
6. Lastly, write the coordinates for both latitude and longitude:
Latitude; Longitude
33° 20’ 39” S ; 25° 15’ 44” E
GRADIENT
GR 11 & 12
GRADIENT:
• Gradient shows the slope of a land. It is the relationship between the
vertical height and the horizontal distance between two points.
• The following formula is used:
𝐺𝑟𝑎𝑑𝑖𝑒𝑛𝑡 =
• Remember that gradient is in METERS
• Answer must ALWAYS be as a ratio ( 1: 1)
𝑉𝑒𝑟𝑡𝑖𝑐𝑎𝑙 𝑖𝑛𝑡𝑒𝑟𝑣𝑎𝑙 (𝑉𝐼)
𝐻𝑜𝑟𝑖𝑧𝑜𝑛𝑡𝑎𝑙 𝑒𝑞𝑢𝑖𝑣𝑎𝑙𝑒𝑛𝑡 (𝐻𝐸)
QUESTION: DETERMINE THE GRADIENT BETWEEN TRG
BEACON 345 IN BLOCK B1 AND POINT HEIGHT 459 IN BLOCK
A2. (On the topographic map)
Step 1: Draw a line between the two points.
Step 2: Determine the VI (Vertical interval) by subtracting the two
points from one another:
𝑉𝐼 = 697,1 𝑚 − 459 𝑚
𝑉𝐼 = 238.1 𝑚
Step 3: Determine the HE (Horizontal equivalent) by measuring the
distance between the two points.
Answer: 6,5 cm
Remember that you have measured to so you must multiply with the scale…
𝐻𝐸 = 6,5 𝑐𝑚 × 500
𝐻𝐸 = 3250 𝑚
Step 4: Substitute the values calculated into the formula:
Remember to always write the formula down..
𝐕𝐞𝐫𝐭𝐢𝐜𝐚𝐥 𝐢𝐧𝐭𝐞𝐫𝐯𝐚𝐥 (𝐕𝐈)
𝐆𝐫𝐚𝐝𝐢𝐞𝐧𝐭 =
𝐇𝐨𝐫𝐢𝐳𝐨𝐧𝐭𝐚𝐥 𝐞𝐪𝐮𝐢𝐯𝐚𝐥𝐞𝐧𝐭 (𝐇𝐄)
238.1 m
Gradient =
(Divide the numerator and the denominator by the value
3250 m
of the numerator)
OR
𝟑𝟐𝟓𝟎
Insert it as follow into your calculator (
)
𝟐𝟑𝟖.𝟏
Step 5: Write your answer as a ratio = 1 : 13,65 (Round off to two decimals)
CROSS SECTION
GR 10 -12
CROSS SECTION:
• A cross section is a SIDE view of a landform or system.
Follow the following steps to draw a cross section:
Step 1: Draw a straight line between the points.
Step 2: Use a strip of paper and place it along the line:
Step 3: Mark off each contour and record its height in meters
Step 4: Draw a graph where the vertical scale is on the y-axis with a scale of 1
cm = 20m and the horizontal scale is on the x-axis.
Remember the following:
• Label your x and y axis
• Write a heading for your graph
Step 5: Place the strip of paper on the horizontal line and plot the heights
to correspond with the heights on the vertical axis. Join the dots to
complete the cross section.
VERTICAL
EXAGGERATION
GR 11 & 12
VERTICAL EXAGGERATION:
• It is difficult to distinguish the difference in the slope if the vertical and
horizontal scales are the same.
• Therefore, vertical exaggeration is the amount by which the vertical scale of
the cross section is bigger than the map scale.
• Mountain areas usually have a smaller exaggeration and flat areas have a
bigger exaggeration so that the relief difference are noticeable.
• Vertical exaggeration is calculated with the following formula:
𝑽𝑺 (𝑽𝒆𝒓𝒕𝒊𝒄𝒂𝒍 𝒔𝒄𝒂𝒍𝒆)
𝑽𝑬 =
𝑯𝑺 (𝑯𝒐𝒓𝒊𝒛𝒐𝒏𝒕𝒂𝒍 𝒔𝒄𝒂𝒍𝒆)
Step 1: Write down the vertical scale.
1 𝑐𝑚 = 20 𝑚
Step 2: Convert the meters to centimenters
in the vertical scale
1 𝑐𝑚 = 20 𝑚 × 100
1 𝑐𝑚 = 2000 𝑐𝑚
Step 3: Write the VS as a fraction:
1
1 𝑐𝑚 = 2000 𝑐𝑚 =
2000
Step 4: Write down the scale of the horizontal axis.
Note topographic map = 1: 50 000 and orthophoto map 1: 10 000.
Lets assume we worked on a topographic map..
1: 50 000
Step 5: Write the horizontal scale as a fraction
1
1: 50 000 =
50 000
Step 6:
Write down the formula:
𝑽𝑺 (𝑽𝒆𝒓𝒕𝒊𝒄𝒂𝒍 𝒔𝒄𝒂𝒍𝒆)
𝑽𝑬 =
𝑯𝑺 (𝑯𝒐𝒓𝒊𝒛𝒐𝒏𝒕𝒂𝒍 𝒔𝒄𝒂𝒍𝒆)
Step 7: Substitute the values for VS and HS in the formula:
𝐕𝐒 (𝐕𝐞𝐫𝐭𝐢𝐜𝐚𝐥 𝐬𝐜𝐚𝐥𝐞)
𝐕𝐄 =
𝐇𝐒 (𝐇𝐨𝐫𝐢𝐳𝐨𝐧𝐭𝐚𝐥 𝐬𝐜𝐚𝐥𝐞)
𝟏
𝐕𝐄 = 𝟐𝟎𝟎𝟎
𝟏
𝟓𝟎 𝟎𝟎𝟎
𝟏
𝟓𝟎 𝟎𝟎𝟎
𝐕𝐄 =
×
𝟐𝟎𝟎𝟎
𝟏
𝐕𝐄 = 𝟐𝟓 𝐭𝐢𝐦𝐞𝐬
To divide a fraction you
can change the sign to
multiply and invert the
fraction..
INTERVISIBILITY
GR 11 & 12
INTERVISIBILITY:
Refers to whenever one place is visible from another place.
Point A is visible so there is
intervisibility.
Point B is not visible so there is
no intervisibility.
CONTOURS AND
LANDFORMS
GR 10 - 12
CONTOUR LINES:
WHAT IS A CONTOUR LINE?
A contour line is a line on a map that join all points of the same height
above sea level.
CHARACTERISTICS OF CONTOUR
LINES:
• Contour lines are imaginary lines;
• Contour lines can never cross one another;
• Contour lines are represented as a brown line on a 1: 50 000
topographical map;
• Contour lines are continuous and closed lines (except if they are at
the side of the map);
• If the landscape is steep, the contour lines are close together;
• Contour intervals indicate the difference in height between
successive contour lines;
• If the landscape is gentle, the contour lines are far apart;
• If the slope is uniform, the contour lines are evenly spaced;
• Contour lines can join to form a single contour line only
where there is a vertical cliff;
• Contour lines never split.
CONTOUR PATTERNS:
GENTLE SLOPES:
• Contour lines are far apart;
• This even spacing is maintained in both up and down slope.
STEEP SLOPE:
• Contour lines are close together;
• This even spacing is maintained in both up and down slope.
CONCAVE SLOPE:
• When the contour lines are close together at the top of the hill and
gentle at the bottom;
• A slope which becomes progressively steeper uphill.
• On a map the Contour lines will be spaced closer with an increase in
height above sea-level.
CONVEX SLOPE:
• When the contour lines are gentle at the top of the hill and close
together at the bottom, this indicate a convex slope;
• A slope which becomes progressively steeper downhill;
• On a map the contour lines will be spaced closer together with a
decline in height above sea-level.
RIVER VALLEYS:
• A valley is formed due to flowing water and result into a V – shaped
landform;
• The V- shape point towards the higher ground (bigger contour
interval).
• In the case of a river valley, the greatest height is to the outer side
and the land sinks down towards the inner side, where the riverbed
is.
V – VALLEY:
• Found in the upper course of a river where the gradient is steep;
• Can be identified on a map by looking a the dominant V of the contour
lines;
• Contour lines are close together.
U- VALLEY:
• Occur in areas where water or glacier erosion has widen the valley floor
to make it a U shape;
• Occur in the middle and lower course of a river;
WATERFALL:
• Forms where there is a sudden drop in the river valley;
• Waterfalls are formed in the upper course of the river;
• When contour lines on a map touch one another or are very close
together as they cross a river or stream, it indicates a waterfall.
SPUR:
• A long, gently sloping strip of ground that runs down from a hill to
lower ground;
• A spur is formed between two river valleys;
• The greatest height is to the inner side and the land sinks down
towards the outer side of the spur.
HILL:
A point or small area of high ground. When you are on a hilltop, the
ground slopes down in all directions.
SADDLE:
• Depression between two peaks or ridges;
• This landform is formed by glaciers or streams that flow close to one
another;
RIDGE:
A line of high ground with height variations along its crest. The ridge
is not simply a line of hills; all points of the ridge crest are higher than
the ground on both sides of the ridge.
MESA:
• A flat-topped hill with steep sides;
• Found in landscapes associated with horizontal strata;
• Contour lines are close together at the top (illustrate the cap rock).
BUTTE:
• Tall flat topped mountain with steep sides;
• Associated with landforms with horizontal strata;
• Greater height than width;
• Smaller flat top.
CONICAL HILL:
• Formed by rivers that cuts through the landscape;
• No cap rock on this type of rock;
• Rounded point at the top, but more gentle than a mesa or butte.