Presentation on theme: "Goddard Sailing Association Laguna 26 Cruiser Qualification Course version 6."— Presentation transcript:
Goddard Sailing Association Laguna 26 Cruiser Qualification Course version 6
GSA Cruiser Qualification Course Part 4 – Piloting and Navigation
Piloting and Navigation Overview Chart reading Buoys and Markers Voyage planning and basic piloting
Chart reading Symbols and colors Compass rose – magnetic variation Water depth, depth contours Lights and light codes Hazards to navigation
Chart Info Lat Long –1 minute of latitude (N-S) = 1 nm = 1.15 statute miles Use dividers on N-S scale for distance measurements –1 minute of longitude (E-W) = 1 nm * cosine (latitude) cos (39°) = 0.78 Markers Selected Headings and distances Various hazards Prominent features on land
Compass Rose Shows True and Magnetic Directions Indicates Variation –And rate of change! Use parallel rule to draw any course on the chart based on the compass rose
South River Chart Blue on chart = < 6’ depth South River Channel = 6’
Crab Pot City South River to Thomas Point
Chart: Annapolis and vicinity X
Channels Charts show depth in Feet, Meters (3.3 ft) or Fathoms (6 ft) –Find out about the chart you are using! Shallower water colors – darker blue –Determine what colors are OK for your boat Channels have a “controlling depth” –Markers usually mark limits at that depth Mean lower low tide (but sometimes is shallower) –South River = 6’, Annapolis harbor = 20’, Ships channel = 40’ Range Marks –Line them up to stay in the channel The basics – “Red Right Returning” –Red (even numbered) buoys or markers on the starboard side when going from larger to smaller water or upstream, green (odd numbered) markers to port. –Red and Green – marks channel junctions. –Light color corresponds to buoy color at night
Buoys and Markers Red Colors, Red Lights, Triangular Shapes, and Even Numbers: These mark the edge of the channel on your starboard (right) side as you enter from the open sea or head upstream. Numbers increase consecutively as you return from the open sea or head upstream.upstream Green Colors, Green Lights, Rectangular Shapes, and Odd Numbers: These mark the edge of the channel on your port (left) side as you enter from the open sea or head upstream. Numbers increase consecutively as you return from the open sea or head upstream. Note: The above marks are often found in red / green pairs, but there may just be individual red or green marks, at the discretion of the Coast Guard (based on the characteristics of the channel). Thus a channel might begin with marks 2 and 4, for example. Yellow Marks (usually identified with a letter): Special Purpose Aids, e.g., Anchorage, Fish Net, etc.
Buoys and Markers (2) Combined Red and Green Colors and/or Lights are placed at a channel split (usually when heading upstream) or junction of two channels (heading downstream). The top color indicates the preferred (primary) channel. Heading upstream, treat the marker as the top color (i.e., keep the mark to starboard in this example) to stay in the primary channel (e.g., a river), or as the bottom color (keep this mark to port) to go into the secondary channel (e.g., a creek). In this case the mark shows that a channel to the creek heads off to the right. The mark is often labeled with an abbreviation of the secondary channel, e.g., “WC” = Weems Creek. Range Marks: Guide into a channel Lower mark is in Front Turn toward lower mark Various colors A Deep Water Mark Mo “A”
Buoys and Markers – “Non lateral” markers Exclusion Area –Crossed diamonds indicate areas off-limits to all vessels such as swimming areas, dams, and spillways. Danger Area –Diamonds warn of dangers such as rocks, shoals, construction, dams, or stumps. Always proceed with caution and keep a safe distance. Never assume that every hazard will be marked by a buoy Controlled Area –Circles indicate a controlled area such as no wake, idle speed, speed limit, or ski zone.no wakeidle speed Information –Squares provide information such as places to find food, supplies, and repairs; and they give directions, distances, and other non-regulatory information. Safe Water Marker –These are white with red vertical stripes and indicate unobstructed water on all sides. They mark mid-channels or fairways and may be passed on either side.
Dead Reckoning Start from a known position (fix) Estimate Track and speed –“Heading” – direction the boat is pointed –“Course” – direction of intended travel –“Track” – actual route travelled –If the knotmeter works… it indicates the instantaneous speed It also has a “knotlog”, i.e., odometer –Include leeway and current – vector sum Current in the Chesapeake is mostly tidal Leeway: the boat drifts downwind as well as moving forward Set: Direction the current is flowing towards Drift: speed of the current –Calculate Course Made Good (CMG) from the above Correct for compass deviation and variation Apply CMG vector to starting point
Your course is 126° true and your speed is 6.3 knots. The current is 162° true at 2 knots. What compass course must you steer to correct for the current (set and drift), Magnetic variation, and compass deviation, to stay on course for your destination? Example: Determining Course to Steer for a Known Set and Drift True Course: 117° Variation: 10° W Magnetic Course:127° Deviation 2° E Steer125° True Course = 117° 162° 126°
LOPs LOP = Line of Position Use boat compass or hand compass to determine the direction to a known mark –Correct for compass variation –Draw the LOP on the chart (parallel rule + compass rose) 2 LOPs intersect at a point –60° to 120° intersection is best 3 LOPs make a triangle. –If it’s small you are probably nearby 1 LOP and depth can also work sometimes A single LOP can be used to avoid a hazard
Chart with LOPs LOPs
Chart Navigation Exercise Using the hand compass, you determine : –The bearing to Thomas Point Light is 320° –The bearing to Bloody Point Light is 195° Questions –What is your location? Lattitude, Longitude? –What is the depth there –What Marker is nearest? What color is it? What else can you tell about it? –What is the heading into Annapolis Harbor? What marker would be on (close to) your course? How far away is this marker?
Running Fix: Gets a fix from a single mark Take an initial LOP on the mark Continue underway until the direction to the mark changes at least 30° Take a second LOP on the mark “Advance” the first LOP by the estimated travel –Parallel to the original LOP but offset by the DR vector –Use parallel rule and dividers The fix is where the second LOP intersects the “advanced” first LOP –Accuracy of this fix depends on the DR accuracy