Navigation is where we try to find our way around
on in a particular place. Just like finding
the road that has less traffic on it, on a busy
morning . Like in a rallycar racing , the navigator
directs the driver as to where the turns are
coming and which roads to take. Exactly how
do we do navigation? Well, by looking at charts
such as maps as well as special instruments
like a compass people can plot a course to travel
to reach their destination. Navigators today
usually use a compass, a map, and an idea of
working out distances. The compass is a very
important and popular tool for navigation. A
compass allows us to determine direction, take
bearings, plot our route of travel on a map,
sight on landmarks for straight-line traveling,
and to detour in the right direction when going
were the first navigators?
we cannot say exactly ,who were the first navigators,
because for years peoples have been journeying
to other places within their own country, in that
sense they would have been called travelers. Navigation
tends to give people the idea of journeying across
the sea to distant lands, one of the more popular
persons of the Western Hemisphere was Christopher
Columbus. Others include people such as Vasco
da Gama ,Marco Polo and Zheng He.
Longitude and stuff like that..
we take an in-depth look at navigators and their
instruments we need to take a further look at
latitudes and longitudes.
of attitudes are imaginary lines drawn around
the earth which are parallel to the equator.
The equator is the longest line it is approximately
40000km. These parallels of latitude decrease
in size as they get closer to the poles.
These lines are identical on either side
of the equator but are identified according
to their position north or south of the
of Longitude are half circle that are drawn
from pole to pole. Meridians are numbered
in degrees from 0° to 180° east or west
of the Greenwich Meridian which is 0°. This
0° meridian also known as prime meridian
goes through Greenwich in London and is
the basis from which all lines of longitude
are measured. This was agreed upon in 1884
at a conference which many nations attended.
after these parallels of latitude and meridians
of longitude combine they for a series of
grids, making able for us to pinpoint a
position on any part of the globe!! To fix
any point using latitude and longitude we
read off the parallel of latitude first
then the meridian of longitude. Of course
if a location is within an area enclosed
by latitude and longitude coordinates the
grid is then divided further into smaller
units called minutes (as in time). One degree
is equal to 60 minutes and vice versa.
of Cancer and Capricorn
equator runs through Indonesia, Ecuador, northern
Brazil, the Democratic Republic of the Congo,
and Kenya, among other countries. Well from
above we see that the equator divides the earth
into two parts which we call hemispheres, the
hemisphere above the equator is the Northern
Hemisphere and the one below is the Southern
Hemisphere. Another important parallel line
23 1/2° north (which puts it in the northern
hemisphere) is called the Tropic of Cancer,
which runs through Mexico, the Bahamas, Egypt,
Saudi Arabia, India, and southern China The
latitude line is 23 1/2° south of the equator
and is called the Tropic of Capricorn which
runs through Australia, Chile, southern Brazil
(Brazil is the only country that passes through
both the equator and a tropic), and northern
South Africa. In between these the Tropic of
Cancer and Capricorn is known as the Tropics.
This area does not have any seasons because
the sun is always high in the sky. Only higher
latitudes, north of the Tropic of Cancer and
south of the Tropic of Capricorn, experience
notable seasonal changes in climate like winter,
spring, summer, autumn.
sun is directly overhead at noon on the Tropic
of Cancer on June 21 (the beginning of summer
in the Northern Hemisphere and the beginning
of winter in the Southern Hemisphere) and the
sun is directly overhead at noon on the Tropic
of Capricorn on December 21 (the beginning of
winter in the Northern Hemisphere and the beginning
of summer in the Southern Hemisphere).
and Antarctic Circles
are also parallels of attitude which occurs
at 66 1/2° north and south of the equator. Within
these circles there is at least one day of the
year when the sun never rises above the horizon
and one day when the sun never sets. When ever
sea-farin' people wanted to determine their
latitude they used a sextant.
What does Sextant
early instrument had a calibrated arc
that is one-sixth of a circle -- a graduated
60° arc. Sex is a prefix that means six,
from the Latin Language.
around the 1700's the sextant (usually made
of wood and brass) was used as a navigational
instrument which measures the angle of celestial
bodies ( like stars, planets, the moon and sun)
above the horizon as seen form the observers
position. By knowing the exact height of a star
above the horizon and the exact time, the observer
can determine the latitude that they are in
and hence their position. Sextants have changed
in design slightly and are still used today.
astrolabe was kind of like the early from of
the Sextant , it too was used to determine the
latitude position of sailors. Astrolabes were
also one of the basic astronomy tools in the
late Middle Ages. It is based off of an ingenious
map made by Greek Astronomer Hipparchus around
150 BC. The astrolabe was popular for more than
200 years because it was reliable and easy to
use on the ship. Mariner's astrolabes are now
very rare and expensive - less than one hundred
are known to survive and most of these are in
poor condition having been recovered from ship
wrecks. Like the quadrants it was used to determine
height of an object such as the sun ,stars etc..
above the horizon. The astrolabe had many other
uses beside this, they could
the time of the day or night by using it as
a mobile sundial or by measuring the altitude
of the sun
the time of the year
the portion of the sky that is visible at
any given time
- Determine the altitude of any object over
simple astrolabe consisted of a disk of wood
or metal with the circumference marked off in
degrees. It was suspended by an attached ring.
Pivoted at the center of the disk was a movable
pointer called by Arab astronomers the alidade.
By sighting with the alidade and taking readings
of its position on the graduated circle, angular
distances could be determined.
name astrolabe comes from the Greek words astron and lambanien meaning
"the one who catches the heavenly bodies,"
or a more familiar term "star grasper"
quadrant was a device for measuring the altitude
of an object above the horizon. It consists
of a flat plate in the shape of a quarter-circle,
with a plumb-line suspended from the apex. The
hand- held quadrant is held in a vertical plane
with the right angle away from the eye and the
curved edge downwards. One of the straight edges
is equipped with a pair of metal pinhole sights
which are aligned with an astronomical object
and the hanging cord reads off the altitude
of this object above the horizon on the circular
scale. It was used in the 15th century to measure
the altitude of a celestial body, usually the
pole star. .
English quadrant or back-staff, first described
in 1595, was a more complex instrument that
measured the altitude of the Sun by the shadow
the quadrant cast. The back-staff was more accurate
than previous instruments, and had the advantage
that the observer had his back to the Sun. It
generally superseded the old quadrant, the astrolabe,
and the cross-staff in the 17th century. A larger
form of quadrant, known as a mural quadrant,
is mounted on a north-south wall and has a solid
arm instead of a hanging cord. The quadrant
had two major limitations:
a windy, rolling deck, it was hard to keep it
exactly vertical in the plane of a heavenly
body. And it was simply impossible to keep the
wind from blowing the plumb bob off line.
are many types of compasses existing today each
developed in a different way. The one we will
focus on is the magnetic compass rose the most
familiar of them all. From about the 1300's
when portolan charts were first developed. The
term "rose" originates from the figure's compass
points resembling the petals of a rose. The
most practical use of the compass at this time
was to identify the direction of the wind to
help the navigator determine which of the eight
winds on the wind rose they were experiencing.
early maps a sixteen point circle was drawn
which represented the major wind directions,
known even today as the 16 Cardinal points.
This diagram resembled the petals of a rows
and was termed the wind rose. When the magnetic
compass came into being it was often placed
on top of the wind rose diagram to help navigate,
later models integrated the wind rose pattern
into the compass assembly, giving us what we
know as the compass rose.
magnetic compass works because the Earth is
like a giant magnet, surrounded by a huge magnetic
field. The Earth has two magnetic poles which
lie near the North and South poles. The magnetic
field of the Earth causes a magnetized 'needle'
of iron or steel to swing into a north-south
position if it is hung from a thread, or if
it is stuck through a straw or piece of wood
floating in a bowl of water. The sixteen cardinal
points of the compass are as follows.
- North North East - North East - East North
- East - East South East - South East - South
South West - South West - West South West
- West- West North West - North West - North
of a compass reading are given in units of "Degrees"
from the Geographic North. , Directions given
are called HEADING or BEARING, by a single number
(0 to 360) each representing degrees of a circle,
measured clockwise from True North.
although the compass is the most widely used
navigational instrument, one of the more 20th
century break thorough is GPS( Global Positioning
Systems). These can be found today in cars,
boats, small airplanes and are available on
the market for everyday individuals.
is a GPS exactly?
or Global Positioning System is based from satellites
about 24 in all forming a network in orbit allowing
for a precise satellite based navigational system.
Originally it was developed by the U.S. Department
of Defense . or military purposes, but was made
available for civilian use in the 1980's by
the government. GPS works in any weather conditions,
anywhere in the world, 24 hours a day. There
are no subscription fees or setup charges to
About the Satellites
these satellites in orbit are 20,000 kilometer
away they can be accurate up to 10 meters
of your location!
are accurate within 1 meter but with special
military approved equipment!!!
GPS satellite weighs approximately 2,000
pounds and is about 17 feet across with
the solar panels extended.
does the GPS System work?
satellites circle the earth twice a day in a
very precise orbit and transmit signal information
to earth. GPS receivers take this information
and use a process called triangulation to calculate
someone's exact location. To give a precise
location at least 4 satellites are used to pin
point a location. Basically the GPS receiver
(whether a handheld or in a car or boat) compares
the time a signal was transmitted by a satellite
with the time it was received by communicating
with the satellites via low power radio signals.
The difference in time tells the GPS receiver
how far away the satellite is. Therefore a GPS
receiver is limited as to where it can function.
It has to be able to "see" the satellites to
calculate latitude and longitude. The simplest
GPS receiver would give you just the coordinates
of your location on Earth in latitude, longitude
and altitude. Remember from above the grid formed
by the lines of latitude and longitude? Altitude
is just a measure of one's distance above sea
level. These GPS receivers uses all of this
information to calculate other stuff like
- How long you've been traveling
distanced you have traveled
current speed and thus
estimated time of arrival at your destination
(providing that you had input your final coordinates)
1 Satellite would only give you an idea of your
distance location (how far you are from the
satellite). Satellite 2 also gives you an idea
of where you are also hence the two circles
intersect narrowing the area a bit. The third
satellite would intersect this area further
where these three lines meet is roughly your
location but often this third line is a bit
far out . The fourth satellite will intersect
at only one point of these other 3 spheres,
giving us our location!
for one they are used in driving like to determine
which road you are one especially when you are
in these big continental country's like the
USA. Large business companies in some countries
have used GPS systems in their vehicles to track
their employee's location and which employee
to dispatch to a customer or job site.
also allow you to chart your course, and estimate
arrival times etc. In boating,especially around
the world races GPS have become important especially
when crossing the vast oceans like the Atlantic,
it allows the crew to track their course, their
direction and make correction if they are to
far off course. Usually they have almost 2 or
three GPs on board as a fail safe in case one
addition scientists are using GPS to track the
movement of the arctic ice caps, the tectonic
plates of the Earth and monitor volcanic activity.
the military uses the accuracy of the GPS System
in tactical maneuvers. Like in Desert Storm
where there was vast expanses of deserts, ground
troops used GPS receivers to navigate to their
targets otherwise they would have become disoriented
especially when sandstorms limited visibility.
GPS receivers are used in several aircraft's,
such as F-16 fighters, KC-135 aerial refuelers,
and B-2 bombers; Navy ships have used them for
rendezvous, minesweeping, and aircraft operations.
is a Map?
map is a graphical representation of a any location.
Maps has a functional use apart from being ,decorative
Maps have been made of the earth's surface,
the moon, a planet, the ocean floor, etc. Maps
show land formations, contours and landmarks
in general. But these can vary depending on
what the map is portraying. Distance on a map
can be determined by the scale, which is shown
by one or more ruled lines that mark off miles
or other lengths of measure. A map can be practical,
directing travelers from one point to another
through confusing landscape, or explaining the
world by attaching specific types of information
to geography. Maps can also entertain and invite
exploration. A person who draws maps is called
use sets of symbols to indicate the placement
of real objects. The legend is a block of text
or a window in which the symbols used on the
map are explained. Legend symbols can include
icons to represent buildings, different colors
to indicate elevation, different types of lines
to indicate borders or roads of varying size,
and dots and circles to show the relative population
of towns and cities. If the details of a map
look unfamiliar, it is helpful to study the
legend before proceeding further.
maps give a reference point to indicate how
a direction on the map corresponds to a direction
in the real world. This is crucial when using
the map to travel between points. A good map
indicates a cardinal direction for such orientation,
usually by an arrow pointing north. Modern maps
usually adopt the convention that the top of
the map corresponds to North, the bottom to
South, the left edge to West, and the right
edge to East