Navigation Flashcards
Earth movements?
23 hrs 56 mins 4 sec for a full turn
=> + 4 mins to have sun in same bearing
Great circle?
Divides earth in 2 equal parts
<=> small circles don’t
Rhumbline?
= Loxodrome:
Crossing all Meridians at same angle
≠ Orthodrome/Great Circle
Special parallels?
because of earth’s inclination by 23.5 degrees
in North winter: earth closest to sun!
Meridian?
Half a Great Circle from pole to pole
How to correct courses?
Draw a compass diagram
Set
(tip of ijmuiden pilot)
[in degrees]
set angle = 60 * Vcurrent / V ship
[deg]
Determine Deviation
- steam around deviation dolphin and compare compass bearing with true bering: delta is CE, so correct by Variation to get deviatin
- sailing through a leading line
- Azimuth (GZV)
- comparing with GPS course only if no leeway and set
Heeling Error
- is maximal on N/S
- is 0 on E/W
- in-between courses: cos (CC)
- HE P and Stb are opposite (Vorzeichen)
- HE proportional to heeling angle
Books for safe navigation
1.Catalogue of BA Charts (world split in areas A to ..)
2. NtM (P = preliminary = pen | T = temporary = pencil)
3. AP 136: Ocean Passages of the World (4 chapters: AO, PO, IO, sailing vessel routes)
4. AP 100: The Mariner’s Handbook
5. Climate Atlas = Pilot Charts (info for every month)
6. Pilots (76 volumes)
7. ALL: list of LIghts and Fog Signals (divided into sailing areas A-P)
8. ATT: Admiralty Tide Tables
9. Atlas of Tidal Currents
10. Admiralty List of Radio Signals (6 volumes) => pilotage requirements in Vol. 6
11. Nautical Almanac
Distiguishing lights
- colour
- period
- character
ALL
Light Characters
- F Fixed
- Oc Occulting (single/group/composite; longer on than off) = opposite to Fl
- ISO Isophase (equal on and off)
- Fl Flashing (single/group/composite)
- LFl (Long flashing of 2 sec+; but less on than off)
- Q Quick Flashing (60/min)
- VQ (120/min)
- UQ (240/min)
Morse U
. . -
You are running into danger
(from e.g. offshore installations)
Safe Water Buoy
(= landfall buoy)
Slow (character) = safe
(LFl; Iso, Oc)
Morse(A)
Direction indicating lines
- Leading Lights: leading line to enter port/fairway
- Lights in line: mark an area, a limit (e.g. fixed mile)
-
Direction lights
3.1 Moiré light = Inogon (yellow arrows on board)
3.2 PEL (Port Entry Light): very sharply defined sector light with very narrow sectors
Ranges of Lights
- Nominal Range NR (compare power between different lights and 1 argument to determine LR in actual visibility)
- Luminous Range LR (to find range of light in actual visibilty; to decide whether to even bother about GR)
- Geographical GR (to find distance from light when it dips)
Overview of Light ranges
graphic
Nominal Range
- Def: distance from which light can be seen when visibility = 10 M so you can see the lighthouse at 10 M, but the light at e.g. 24 M or 8 M!
-
Use:
2.1 when start looking for what
2.2 find luminous range - Depends on: bulb strength
- Where to find: Chart, ALL
Luminous Range
- Def: distance from which light can be seen in actual visibility (guess; weather forecast; radar ship/shore)
- Use: whether to start looking for the light (LR has to be ≥ GR)
- Depends on: bulb strength (=NR) and actual visibility
- Where to find: Luminous Range Diagram (enter with arguments = nominal range and actual visibility)
Geographical Range
- Def: distance from which light can be seen in the horizon (= dipping light) as long as LR ≥ GR
-
Use:
determing distance to the light => fix (distance + true bearing)
duck&run -
Depends on: arguments =
3.1 elevation
3.2 height of eye - Where to find: Geographical Range Table at beginning of ALL
Duck&Run
Blink
Distance of horizon
Geographical Range Table
Blink
Requirements of a sea chart
- Rhumb Line (=loxodrome) are represented as a straight line ( => Parallels and Meridians also have to be straight lines)
- Chart needs to be conformal (angular s in reality are similar to angles on the chart => Parallels and Meridians are perpendicular)
- Distances easy to measure (take on sides)
- Small change of scale (Africa, Groenland)
Mercator projection
Smash the Mandarine!
Mercator projection
Smash the Mandarine!
Different chart names:
Scale of charts
From small scale
Track Charts (North Sea)
Course Charts
Coastal Charts
Plan Charts (Port)
to large scale
Chart: title
Datum: mostly WGS84
BA charts: colourful = m ; grey/blue: fathoms and feet
Chart datum: heights based on very high tidal level <=> depth based on very low tide (LAT)
Natural Scale: at a specified latitude => fruther away from equator: larger scale <=> closer to equator: smaller scale
Rules re bearings
- only TB in chart
- don’t draw through lighthouses
- you are always on the 2nd bearing line
- you are usually not on your course line
.
Getting a distance
- duck&run
- radar
- sextant (height; elevation)
- guess/experience
Running Fixes
- angle ≥ 30 deg
-
inaccuracies are in the advancing
=> reduce time between bearings
=> reduce distance error
Cardinal buoys
Q.130
Extraordinary buoys
In NL/D: all Safe Water buoys on 10 m contour
New Danger Racon: • - -
10 methods for a fix
1 point - 1 bearing
1. Bearing w distance
2. Bearing w sounding
- Bearing w LOP (Line of Position - GZV)
1 point - 2 bearings
4. Running fix
5. double angle bearing: 4 point bearing (=4x11.25 = 45 deg) or any doubled angle
bearings on 2 or more points
6. 2-point bearing (2+ bearing lines)
7. Running 2-point = running cross bearing
(8. 2 distances)
9. Snellius
(10. Sounding note (record sounding profile over time))
Double angle bearing
Distance travelled between doubling of bearing of an object equals the distance from that object at the time of the 2nd bearing.
Bad helmsman = Counter current: you covered less distance than you thought => closer to lighthouse
From Cardinal Points to By-Points
5 basic rules of Safe Navigation
- Never trust just 1 system
- Determine your position regularly
- LLL: log, lead, lookout
- always use largest scale for particular area
- always put a course line in the chart
Verifying 2-point bearing by 3rd bearing line
=> triangle
=> turn all 3 bearing lines in the same direction until they intersect
=> N-> E; S-> W
Rules for taking bearings
- as perpendicular as possible
- first take bearing forward, then aft (relative moving; take time of most abeam)
- use deviation of CC, not of bearing!!!
- take and plot bearings in regular intervals
- note time
- only take bearings of fixed objects, not buoys/platforms
- inaccuries caused by advancements
Piloting?
position finding by means of bearings
sqat
formula
squat = Cb x v^2
e.g. 0.8; 10 kn => .8 m!
Graphic
Tide ./. Draft
Springs ./. Neaps
Spring: New and Full moon
Neaps: sun&moon perpendicular
Age of tide: time between Full or New moon and Spring (depending on location from southern ocean) => waves rolling into Atlantic-> Amphidromic points (of 0 tidal hub)
ALL buildup/structure
Elevation ./. Height
sector lights ./. alternating lights
if you remain stationary, you only see the same colour of a sector light <=> but the colours will change in an alternating light
Al. will change colour within the period
Compass Observation Book
Record deviations found during navigation by observations.
Record, instead of promptly changing Deviation Table. Could be temporarily
