How do we describe a location on
Earth?
Geodetic reference system
How do we define the shape of the
earth?
Definition of the sphere:
A three-dimensional surface, all points of
which are equidistant from a fixed point.
The Earth as a sphere...
Rotational axis
North pole
Poles =
ends of the earth's
rotational axis
Ecuator
Equator = an imaginary line
on the Earth's surface
equidistant from the north
pole and south pole
South pole
Meridians
= Great circles that all meet at the North and South poles
Prime meridian = 0 degrees,
passes through Greenwich
Ranges: 0-180 degrees W
0-180 degrees E
Longitudes
= The angle between the plane of the prime meridian and that of the meridian
through a point. East-west direction.
3
1
Longitudes
1 = 15W
2
2 = 15E
3 = 135W
4
4 = 90W
Longitudes  the position in E-W
direction
2
What is the
approximate longitude
of point 1?
1
How about point 2?
Note 1:
In computers, West have negative
values and East positive values:
Lon: 15W = -15
Note 2:
Always use W/E in written form:
Lon: 15W, not -15
Parallels
Imaginary lines running around the earth parallel to the Equator. The
equator corresponds the great circle perpendicular to the Earth's axis,
determining the division of the Earth in two hemispheres:
North and South
5 major parallels:
Arctic cirle
Tropic of Cancer
The Equator, the 0 parallel
Tropic of Caprion
Antarctic Circle
Latitudes
The latitude of a point on the Earth's surface is the angle between the
plane of the equator and the straight line segment that joins the point
to the center of the globe.
0 - 90 N
0 - 90 S
Note 1:
Computers, North is positive,
South is negative:
Note 2:
Always use N/S in written form:
lat: 15S = -15
lat/ 15S, not -15
Latitudes
 gives the position in N-S direction
2
What is the approximate
latitude of point 1?
1
How about point 2?
Definition of the Swedish plane coordinate system
150°W
180°
135°W
165°E
120°W
Spherical coordinate
system
on the Earth
150°E
105°W
135°E
90°W
Coordinates in latitute
and
longitude
120°E
75°W
105°E
60°W
90°E
45°W
75°E
30°W
60°E
15°W
45°E
0°
15°E
30°E
A transverse
cylindrical
projection
Parallels and
meridians are no
longer straight lines
in a Cartesian
coordinate grid
15°W
We need a
plane
Cartesian
coordinate
system
0°
15°E
45°E
60°E
60°N
60°N
45°N
45°N
30°N
Example:
The Swedish
national
system: RT90,
2.5 gon W
15°N
15°N
0°
0°
15°W
0°
15°E
30°E
45°E
15°W
We define an
origo
0°
15°E
45°E
60°E
60°N
60°N
45°N
45°N
30°N
15°N
15°N
0°
0°
15°W
0°
15°E
30°E
45°E
15°W
7500000
We define an
origo
0
0°
15°E
1500000
45°E
60°E
60°N
6000000
3000000
7500000
-1500000
60°N
45°N
6000000
-3000000
45°N
4500000
We create
the grid
15°N
15°N
0°
0°
15°W
-4500000
-3000000
0°
-1500000
15°E
0
30°E
1500000
45°E
3000000
0
0
1500000
1500000
We get
negative
coordinates in
western
Sweden !
3000000
3000000
30°N
4500000
-4500000
0
1500000
15°W
15°E
45°E
60°E
6000000
60°N
60°N
45°N
45°N
4500000
We create
the grid
4500000
30°N
3000000
3000000
15°N
0
1500000
1500000
15°N
0°
0°
15°W
-3000000
-1500000
0°
15°E
0
1500000
30°E
3000000
45°E
4500000
0
We add a
number
(1500000 m) to
all xcoordinates.
=
False
Easting
6000000
7500000
We define an
origo
0°
3000000
7500000
-1500000
4500000
-3000000
0
1500000
0°
15°E
45°E
60°E
60°N
6000000
RT90, 2.5
gon W
4500000
60°N
45°N
6000000
7500000
15°W
3000000
7500000
-1500000
4500000
45°N
3000000
3000000
30°N
4500000
-3000000
15°N
0°
0°
15°W
-3000000
-1500000
0°
15°E
0
1500000
30°E
3000000
45°E
4500000
0
0
1500000
1500000
15°N
Plane, cartesian
coordinate system
National e.g.
RT 90, 2.5 gon W in Sweden
Coordinates in
x and y, meters
To bring
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Warm clothes
Rain protection
Wellington or hiking boots
Bed sheets, (not sleeping bag), towels
Other hygiene stuff (not perfume)
Medication
•
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Note book
Hard folder for papers
Pencils
Compass
Small backpack
Extra socks
Tic – picker
•
•
Illness
Water scarcity