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Social sciences

Geography

Map work

Grade 9

Module 13

Magnetic north map skills

You became acquainted with basic map skills in Grade 8 and did exercises that involved the 1:50 000 topographic map of Alice. In doing that, you learned to:

determine location

gauge accurately and determine direction

calculate distance by making use of a scale

explain the naming of a map

recognise conventional map symbols

recognise representation of height on maps

identify contour patterns

This knowledge, together with what you will still be acquiring in using the 1:50 000 topographic map of Bloemfontein and a 1:10 000 orthophoto map of a portion of this will see you through this year’s work.

Before commencing the practical exercises, you have to learn a number of additional map skills.

Calculating distance on an orthophoto map.

Orthophoto maps are always drawn to the scale of 1:10 000. Follow the steps to determine distance:

Accurately measure the distance between two points in centimetres, using a ruler (or using a string if the line to be measured curves);

Convert this distance to kilometres or metres, depending on what is required.

Example

A________________________________B

The length between A and B is 10 cm.

Scale 1 1:10 000

What is the true distance in km?

10 cm x 10 000

100 000 cm ÷ 100 000

1 km

What is the true distance in m?

10 cm x 10 000

100 000 ÷ 100

1000 m

Why do we divide by 100 000 and 100?

The metrical units of measurement can be represented as follows:

Km Hm Dm M dm cm mm
1 0 0 0 0 0
1 0 0

We therefore have 100 000 cm in 1 km

and

100 cm in 1 meter

You may therefore follow the shorter method if you can remember that the scale of

1 : 10 000 is the same as:

1 cm = 10 000 cm

1 cm = 100 m (÷ 100)

1 cm = 0,1 km (÷ 100 000)

Activity 1: [lo 1.3]

  1. Calculate the true distance in metres if the distance on a 1:10 000 orthophoto map is as follows;
  1. 5,8 cm.
  2. 10,1 cm.
  3. Calculate the true distance in kilometres if the distance on a 1:10 000 orthophoto map is as follows;
  1. 92,2 cm.
  2. 15,6 cm. Magnetic North and Magnetic Declination

You have learnt how to gauge accurately in Grade 8. Remember the steps that have to be followed:

Connect the two points by means of a pencilled line.

  • Draw a line to show True North through the point FROM which you have to measure.
  • Position the protractor by placing 0° against the line indicating north and the centre at the point from which the measurement is to be taken.
  • Measure the angle clockwise from the line for north to the connecting line (pencilled line of Step 1.)

Example:

On a map, North therefore indicates the North Pole, which we refer to as TRUE NORTH (geographic north.)

The earth also has a magnetic field that extends from north to south, for which we use a compass. The earth’s magnetic field does not correspond exactly with the true North and South Poles. North as indicated by the compass will always lie WEST of TRUE NORTH (TN) and is known as MAGNETIC NORTH (MN).

The difference between true north and magnetic north is known as the MAGNETIC DECLINATION (MD). The Magnetic Declination differs from place to place and continuously increases and decreases at any place, because magnetic north is not a fixed point.

To make it possible to determine the Magnetic Declination of any place, the following information is given in the margin of a 1:50 000 topographic map:

Example:

Calculate magnetic declination as at present:

Step 1:

Calculate the difference in years = 2003 – 2000

= 3 years

Step 2:

Multiply the years by the annual difference in minutes = 3 years x 4'

= 12'

Step 3:

Determine whether the angle increases (eastwards) or decreases (westwards).

Eastwards (smaller) -

Westwards (bigger) +

Step 4:

Add the minutes (westwards) or subtract them (eastwards).

In this instance it is eastwards, therefore:

21°30' - 12'

= 21°18' West of True North

REMEMBER that there are 60' in 1°.

If you should have to subtract and find that the degrees to be subtracted are too many, you “borrow” 1° and convert it to minutes.

Example:

21°30' – 34'

20°90' - 34'

= 20°56' West of True North.

If you should have to add minutes and get an answer that is more than 60’, you have to convert it 1°.

Example:

21°30' + 34'

21°64'

= 22°04' West of True North.

Step 5:

Remember to write West of True North alongside the new declination, because Magnetic North ALWAYS lies WEST of True NORTH.

Magnetic North

To gauge Magnetic North between two points, the degrees of TRUE NORTH must be added (+) to the Magnetic Declination and the answer must be written in degrees:

Example:

TN + MD = MN

50° + 21°18' = 71°18'

Assessment

Learning Outcomes(LOs)
LO 1
Geographical EnquiryThe learner will be able to use enquiry skills to investigate geographical and environmental concepts and processes.
Assessment Standards(ASs)
We know this when the learner:
1.2 asks questions that are relevant for identifying sources;
1.3 draws conclusions and makes analyses to obtain information from sources such as photographs, maps, atlases, graphs and statistics;
1.4 correlates information from different sources;
1.7 reports on knowledge that they have obtained through research, making use of different sources of information.
LO 2
Geographical Knowledge and UnderstandingThe learner will be able to demonstrate geographical and environmental knowledge and understanding.
We know this when the learner:
2.2 identifies ways in which Science and Technology have contributed a positively and negatively influence to development (people and resources.)

Memorandum

ACTIVITY1:

  • 580 m
  • 1 010 m
  • 9,22 km
  • 1,56 km

ACTIVITY2:

1. True North / Bearing :

Magnetic Declination:

1990 – 2003 = 13 years

13 × 2’ = 26’ westwards

18 0 41’ + 26’ (westwards)

= 18 0 67’

= 19 0 07 west of true north

Magnetic Bearing: WN + MD = MN

…… + 19 0 07 = ………………………..

  1. Actual Bearing :

Magnetic Declination: 1993 – 2003 = 10 years

10 × 3’ = 30’ eastwards (-)

20 0 15’ – 30’

19 0 75 – 30

= 19 0 45’ west of true north

Magnetic Bearing: WN + MO = MN

...................... + 19 0 45 =..................................

Questions & Answers

Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
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Source:  OpenStax, Geography grade 9. OpenStax CNX. Sep 14, 2009 Download for free at http://cnx.org/content/col11057/1.1
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