Lesson04.ppt

1、Lesson 4: Visual Navigation Aids,Learning Objectives,Know the identifying characteristics and significance of lighted aids to navigation Determine computed visibility of a navigational light Be familiar with the shapes and lights of the International Association of Lighthouse Authorities (IALA) Comp

2、rehend the use of buoys and beacons during piloting,Nav Aid: Any device external to a vessel or aircraft intended to assist in determining position and safe course, or to warn of dangers or obstructions.,Significance of Nav Aids,DAYTIME Location Shape Color Scheme Auxiliary features Special Markings

3、,Identification of Navigation Aids,NIGHT (Lighted) Phase characteristic Period Color,Color (red, green, yellow, or white) Period (length of time to complete one cycle) Phase Characteristics (pattern of light) Chart Symbol Fixed F Flashing Fl Quick Flashing Qk Fl Group Flashing Gp Fl Morse Code Mo (A

4、) Occulting Occ,Identification of Navigation Aids (at night),Lighted Nav AidsPhase Characteristics,Lighted Navaids: Lighted navaids have purple exclamation point ! or 1/8” purple circle over black dot. Floating vs. Fixed Navaids: Fixed Navaids in ROMAN text Floating Navaids in italics text Flashing

5、Navaids: Numbers indicate patterns of light flashes Occulting: numbers indicate the pattern of eclipses eg. F Gp Fl (2+3) or Gp Occ (2+3),Chart Symbology for Lighted Nav Aids,Special Purpose Lights,Alternating Lights change color following a regular pattern airport beacons, harbor entrance lights,Ci

6、vilian airport marker beacon,Special Purpose Lights,Sector Lights Used to warn of hazards to navigation when approaching the light from certain sectors red light used in dangerous sectors sector limits are expressed in degrees true as observed from a vessel, not from the light!,120,045,Special Purpo

7、se Lights,Range Lights used to mark straight reaches of a channel,Purpose: To be able to determine, in advance, when you should expect to gain or lose sight of a navaid during a coastal transit. Computed visibility = The maximum distance at which a light can be seen given the current meteorological

8、conditions. NOTE: Computed visibility Meteorological Visibility,Determining the Computed Visibility of a NavAid,Horizon distance = the LOS from a position above the earths surface to the visual horizon. Luminous range = the maximum distance at which a light may be seen under under the current meteor

9、ological conditions, independent of elevation and curvature of the earth. Nominal range = a special case of the luminous range. It is the distance a light could be seen in “clear” weather. Also called the charted range. Geographic range = the maximum distance that a light may be seen in perfect visi

10、bility , taking into consideration, elevation, height of eye, and curvature of the earth. Computed visibility = The maximum distance at which a light can be seen in the current meteorological conditions, taking into consideration the elevation, height of eye, and curvature of the earth.,Definitions,

11、STEP #1: Determine Luminous Range Nominal Range (From Chart or Light List) Meteorological Visibility (Given) Luminous Range (From diagram),Determining the Computed Visibility of a NavAid,23 NM,5.5 NM,STEP #1: Determine Luminous Range Nominal Range (From Light List) Meteorological Visibility (Given)

12、Luminous Range (From diagram),Determining the Computed Visibility of a NavAid,23 NM,5.5 NM,14.8 NM,STEP #2: Determine Geographic Range Height of Light (From chart or Light List) Height of Eye (known) Geographic Range (from Geographic Range Table, pg 96 ),Determining the Computed Visibility of a NavA

13、id,98 Ft,52 Ft,STEP #2: Determine Geographic Range Height of Light (From chart or Light List) Height of Eye (known) Geographic Range (from Geographic Range Table, pg 96 ),Determining the Computed Visibility of a NavAid,98 Ft,52 Ft,20 Ft,STEP #3: Determine Computed Visibility Compare LR (step 1) with

14、 GR (step 2) If LR GR, then computed visibility = CR If GR LR, then computed visibility = LR LR = 14.8 NM GR = 20 NM COMPUTED VISIBILITY =,Determining the Computed Visibility of a NavAid,14.8 NM,S 15,C 090,LIGHT,Computed Vis 14.8 NM,Buoys and Beacons,Warn navigator of dangers, obstructions, or chang

15、e in contour of sea bottom Indicate safe limits of a channel Two general buoyage systems Cardinal Lateral,Cardinal System of Buoyage,Uniform Cardinal System of Buoyage Method: indicate the approximate true bearing of safe water from the danger it marks. Uses: Mark offshore rocks, shoals, and islets.

16、 Mark dangers in and near the open sea.,Lateral Systems of Buoyage,Lateral Systems of Buoyage Method: indicate the direction of danger relative to the course that should normally be followed. Uses: Indicate sides or junctions of navigable channels Indicate the safe side on which to pass a hazard Mar

17、k the approx. centerline of wide bodies of water,IALA Systems(International Association of Lighthouse Authorities),US Lateral System “IALA B” Red buoys mark the starboard (right) side of channels When returning from seaward Green buoys mark the port (left) side of channels When returning from seawar

18、d “Red, Right, Returning” “Even red nuns have odd green cans” North, Central, South America, Korea, Philippines Uniform Lateral System “IALA A” The opposite of above Europe, Africa, Asia, Australia,IALA Buoy Classification,Construction Can Nun Lighted Sound (bell, whistle, gong, horn) Combination Fu

19、nction Channel Special Cardinal,Construction,Can Buoys: Unlighted, cylindrical shape of a can Nun Buoys: Unlighted, shaped like a truncated cone Lighted: Metal float with a tower on top. Battery operated lantern on top of the tower. Sound: Frame-like construction fitted with a sound-making device Co

20、mbination: Sound and light,Channel Buoys,Function,Safe Water Buoys,Preferred Channel Buoys,Special Buoys,Used to mark: Prohibited areas Limits of fish traps Cable crossings Anchorages Color is yellow Usually unlighted,RACON Buoys,RACONs are used in the U.S. for the following: to identify aids to nav

21、igation, both seaborne (e.g. buoys) and land-based (e.g. lighthouses) to identify landfall or positions on inconspicuous coastlines to indicate navigable spans under bridges to identify offshore oil platforms and similar structures,Beacons,Navaids rigidly attached to seabed or shore Beacons are marked in the same