Grids and Geographic Coordinates

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Grids and Geographic Coordinates
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Grids and grid coordinates

• The geographic grid systemwas created to locate
  allplaces on Earth.
• It uses latitude andlongitude to describe the
  location of any place on Earth.

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Grids and grid coordinates

• One way of mappingthe world is on a
  globe,because Earth is a sphere,which is a 3D
  shape.
• A map is usually a 2D drawing, and shows an
  accurate image of a place.
• Most people find 2D mapseasier to use than
  globes.

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Grids and grid coordinates

• Grids and geographic coordinates are used to
  locate places on a map.

Grids are evenly spaced horizontal and vertical
lines placed on a map.
Letters or numbers are placed along the sides of
a grid. They are combined to give grid
coordinates for any location.
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Grids and grid coordinates

• Why is it useful to be able to quickly locate
  places on a map?

When have you had to locate places on a map?
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Grids and grid coordinates

• Maps in atlases and street directories are common
  examples of where you might use grid coordinates.

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Grids and grid coordinates

• On this map, the grid coordinates are
  alphanumeric.

Alphanumeric means a combination of letters and
numbers.
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Grids and grid coordinates

• On this map, the grid coordinates are
  alphanumeric.

What common type of map generally uses
alphanumeric coordinates?
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Grids and grid coordinates

• Locate the sports oval at Blair College.

The grid coordinate is C3.
The oval is easily located within the square
bounded by the grid coordinates.
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Grids and grid coordinates

• Note that the coordinate for the horizontal grid
  lines is given first, and the vertical grid
  coordinate second.

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Eastings, northings and area references

• The numbers that refer to the vertical grid lines
  are called eastings.

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Eastings, northings and area references

• They increase in value as you move across in an
  easterly direction.

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Eastings, northings and area references

• The numbers that refer to the horizontal grid
  lines are called northings.

They increase in value as you move up in a
northerly direction.
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Eastings, northings and area references

• The two eastings numbers are joined with the two
  northings numbers to make a four-figure area
  reference.

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Eastings, northings and area references

• For example, a symbol is located at eastings 46
  and northings 22, so its area reference is 4622.

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Grid references

• Grid references locate places on a map more
  accurately than area references.

A grid reference is a six figure number, made up
of a three-figure eastings reading and a
three-figure northings reading.
A grid reference is found by mentally subdividing
each grid square into tenths.
The third figure in each eastings and northings
reading is found by estimating how many tenths
across or up the exact location is.
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Grid references

• What is the grid reference for the Post Office?

Answer 283579
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Grid references

• Name the feature at 280570.

Answer An island
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Grid references

• Name the feature at 258576.

Answer The river mouth
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Grid references

• Find the Grid Reference for numbers 1- 4

4
1
2
3
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Grid coordinates latitude and longitude

• To locate different places around Earth, we use
  geographic coordinates measurements of
  latitude and longitude.

Lines of latitude are imaginary parallel lines
that circle the globe in an eastwest direction.
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Grid coordinates latitude and longitude

• The Equator divides Earth into northern and
  southern hemispheres.

Latitude measures how many degrees north or
south a point on Earth lies from the Equator.
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Grid coordinates latitude and longitude

• What is the name given to the imaginary line of
  latitude at

23.5O south of the Equator?
Tropic of Capricorn
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Grid coordinates latitude and longitude

• What is the name given to the imaginary line of
  latitude at

23.5O north of the Equator?
Tropic of Cancer
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Grid coordinates latitude and longitude

• What is the name given to the imaginary line of
  latitude at

66.5O south of the Equator?
Antarctic Circle
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Grid coordinates latitude and longitude

• What is the name given to the imaginary line of
  latitude at

66.5O north of the Equator?
Arctic Circle
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Grid coordinates latitude and longitude

• Lines or meridians of longitude are imaginary
  lines between the North and South Poles.

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Grid coordinates latitude and longitude

• Longitude measures how many degrees east or west
  a point on Earth is from the Prime Meridian.

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Grid coordinates latitude and longitude

• The Prime Meridian is the meridian of longitude
  at 0O. It divides Earth into eastern and
  western hemispheres.

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Grid coordinates latitude and longitude

• What is the name given to the imaginary line at
  180O from the Prime Meridian?

International Date Line
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Grid coordinates latitude and longitude

• Find out why it is given this name.Suggest why
  it is this shape.

International Date Line
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Grid coordinates latitude and longitude

• The exact location of any place on Earth is
  given by its geographic coordinates.
• You can find examples in the index of your atlas.

Measurements for latitude and longitude are given
in degrees (and minutes).
Latitude is stated first, then longitude.
Sydneys geographic coordinates are 33.52S
151.10E