celestial navigation, Schemes and Mind Maps of Astronomy

Download celestial navigation and more Schemes and Mind Maps Astronomy in PDF only on Docsity! INTRO TO NAVIGATION ASSIGNMENT BPS: 0002525 Q 1. Discuss the following onto details. (i) Buoyage system (ii) Marine sextant (iii) Marine chronometer Buoyage system Buoyage system is a system that consist of lateral, cardinal and other marks which are discussed into detailed. Firstly, buoyage system is made up of lateral, cardinal and any other buoys, such as isolated hazards and safe water marks. The colour of their light and flashing sequence made it distinguished from the each other. The colour and the combination of colours on the buoy and the shape of the top-mark. Addition to that, the lateral buoys mark is a well defined channels and indicate port on starboard hand-sides of the route to be followed, for port hand-marks the buoy and light are coloured red, and for starboard marks are green, however, the cardinal buoys are used in together with a compass to indicate where a mariner may find the best navigable water. They are coloured yellow and black with a white flashing lights. To build up with more details, with the aim of improving the safety of navigation to act as a barrier to dangers to shipping and solving the differences of opinion, efforts were made to establish a single set of rules and regulations by International Association Of Marine Aids To Navigational And Lighthouse Authorities (IALA). Which gave mariners the choice of using red to port or red to starboard on a regional basis. Furthermore, for the sake of maintaining uniformity in buoyage system worldwide, (IALA) divided the world into two regions, thus (A) and (B) regions. Region A consist of Europe, Australia, New-Zealand, Africa , the Gulf and some Asian countries, whereas Region B is made up with North, South, Central America, Japan, Korea and the Philippines. Again,(IALA) proposed a system allowing the use of lateral Marks in each region, but whereas in region A, the colour red of the lateral system is used to mark the port side of channels and the colour green for the starboard side. And in region B, the colours are reversed. Regional variations do not pertain to cardinal and isolated danger markings, or to safe water-marks or special marks. There are differences in lateral marks, thus, the colour and the light. The characteristics used for lateral marks are as follow. (IALA) region (A) port lateral marks and lights are coloured red. (IALA) region (A) starboard lateral marks and lights are coloured green. On the other side, (IALA) region (B) port lateral marks and lights are coloured green. IALA starboard lateral marks and lights are coloured red. To continue, lateral marks indicate the port and starboard sides of navigable channels. Also there are similarities in all other types of buoy, aside from the different lateral marks, both system use identical cardinal, isolated danger, safe water and special marks. (ii) Marine sextant Marine sextant is an extremely accurate navigational tool and can precisely measure an angle and is much well discussed below. First and foremost, marine sextant is an instrument for measuring the angular distance between two visible objects, primarily used for measuring the angular distance between two an astronomical object and the horizon in astronavigation. In addition it is the a complex system of mirrors that enhances the navigator’s ability to make measurements. The use of mirrors permits the user to observe and measure the angular distances between two objects simultaneously. Moreover, sextant can not be discussed without fishing out the origin. The device a long history. John Bird made the first sextant in 1757. Amiral John Campbell found that Hadley's octant proved to be not so useful in the trials of the method of lunar distances between Angular distances between the moon and other celestial bodies, because the 90 degrees angle subtended by the arc if the instrument was insufficient. He proposed the angle be increased to 120 degrees, thus creating the sextant. The sextant that are used actually have a little over 130 degrees. One may ask, how does the sextant work?. As already mentioned in the above , sextant uses two mirrors. And if the mirrors is half silvered which enables lights to pass through it. While using the sextant the navigation also uses mirrors to see the horizon. The other mirror is joined to an arm that is moveable. The mirror is move by the help of the arm so that it van be brought to such a position where the object reflected on the mirror superimposes on the line of the horizon, then the readings are taken from the scale which measures the angular distance between them. To build upon, this is how the sextant is used; GPS or Global Positioning System has almost taken over the use of sextant nowadays. This is because, using a sextant is a complicated process it requires calculating, referring to tables, and an in-depth understanding of the sky and earth, and of course a bite if common sense. Despite its complexity the basic rules stand fairly straightforward. To find the latitude you must measure the angle between the previously mentioned method. You should be doing this as the sun is at its highest, thus noon. Your tables will tell you the line of latitude on which the sun should be on that particular day.