Navigation.. Huh?????

Well, 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 around obstacles.

Latitude, Longitude and stuff like that..

Before we take an in-depth look at navigators and their instruments we need to take a further look at latitudes and longitudes.

Tropic of Cancer and Capricorn

The 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.

The 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).

Arctic and Antarctic Circles

These 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.

Invented 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.

Source:http://www.muohio.edu

Source: http://www.arches.uga.edu

The 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

• Measure the time of the day or night by using it as a mobile sundial or by measuring the altitude of the sun
• Measure the time of the year
• Calculate the portion of the sky that is visible at any given time
• Determine the altitude of any object over the horizon.
  

A 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.

Source: http://www1.minn.net

The 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. .

The 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:

On 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.

There 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.

On 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.

A 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.

Source: http://aerocompass.larc.nasa.gov

• North - North North East - North East - East North East
• East - East South East - South East - South South East
• South-South South West - South West - West South West
• West- West North West - North West - North North West

Units 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.

Well 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.

What is a GPS exactly?

GPS 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 use GPS.

How does the GPS System work?

GPS 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
• The distanced you have traveled
• Your current speed and thus
• The estimated time of arrival at your destination (providing that you had input your final coordinates)

Why Four Satellites?

Well 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!

Uses of GPS

Well 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.

They 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 stops working.

In addition scientists are using GPS to track the movement of the arctic ice caps, the tectonic plates of the Earth and monitor volcanic activity.

Also 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.

What is a Map?

A 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 a cartographers.

Legend

Maps 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.

Direction

Most 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