New Update Your Charts and Pilots On-line
Go to the following sites to update your charts and pilots:

Ken Olum's Web Site
This private web site lets you type in the chart number & edition to obtain update information. Ken Olum scan the Notice to Mariners to get all the changes.

Imray Charts web site
Update your Nautical Pilots.Very comprehensive site that give advice on anchoring in coral, and among other things, the growing menace of Piracy against yachts.You can also order Admiralty charts here. Go to 'Browse Imray publications by category' Click on 'Search' button and select your specific Nautical Pilot then follow the 'Corrections' link. Update Example: Pacific & Indian Ocean Pilots : Red Sea Pilot

The National Information and Mapping Agency website.

Charts & Notices To Mariners: Updates by modem.
How to update your Charts & Notices to Mariners by logging onto the NAVINFONET BBS in Washington , D.C. Just follow the instructions.

GPS Info Links NEW

Navigating Latitude
In a world lacking GPS or inertial navigation systems, latitude was a discovery of immense usefulness in navigation. This site tells the tale in a curiously casual fashion.

National Imagery & Mapping Agency
Marine Navigation Dept.
A comprehensive compilation of navigational data including (Adobe Acrobat Reader required to read some of the documents):

US Notice to Mariners

Sailing Directions (Enroute and Planning Guides)

The American Practical Navigator-Bowditch (Pub No. 9) *

NIMA List of Lights

USCG Light List

US Chart No. 1

International Code of Signals (Pub 102)

Radio Navigational Aids (Pub 117)

World Port Index (Pub 150)

Distances Between Ports (Pub 151)

Maneuvering Board Manual (Pub 217)

Radar Navigation Manual (Pub 1310)

Sight Reduction Tables (Pubs 229 and 249) *

Jacky Wong's Navigation Page
This is a very informative site on Ocean Navigation for large and small ships. Principle applies to cruising sailboats as well. Works better if your Web Browser support JavaScripts.

Want To Learn More About GPS?
Check out my GPS Documents Page. You'll find many links to Web resources on the subject of how does the GPS system work, accuracy of GPS systems, list of GPS manufacturers, software for GPS, consumer reviews and more.

Celestial Navigation
Go to Omar F. Reis NavegadorLight Web Site to learn the fundamental theory of Celestial Navigation on-line. Sorry, to be proficient you will still have to go to sea to practice. Also check out the On Line Nautical Almanac and the Navigator software.

Noon Sights
The Sun is overhead, what will you do for your noon position ? Jacky Wong tells you how.

Plotting Sheets
Learn how to make your own plotting sheets with simple tools. Come in handy if you ran out in the middle of the Ocean or just like to save money.

Sight Reduction Work Sheets
I developed this WorkSheet to help me record and organize my daily celestial sights. It may help you too.


Piloting Formulas:

First Bearing
2nd Bearing
Dist.Off 2nd
Dist. Off Abeam

Bow & Bearing

Distance Run
Distance Run

Bow & Bearing

Distance Run
Distance Run

Double Angle

2 * First Angle
Distance Run

Seven Eights

Distance Run
7/8 (0.875) * Dist.Run

Seven Tenths

Distance Run
7/10 (0.7) * Dist.Run


1.4 * Dist. Run
Distance Run

TIME / SPEED / DISTANCE ( In Hours, Knots , Nautical Miles)

Distance = Speed * Time * ((60, for minutes) or (3600, for seconds))


THE RULE of 60

Distance Abeam * 60 = Bearing on the Bow * Range

TIME at 1 Mile = 60 / Speed

SPEED = (SQRT Bow Wave Length) * 1.33

DISTANCE at 6 Minutes = 1/10 (0.1) * Speed


DISTANCE TO HORIZON = 1.15 * SQRT of HE (HE=Ht. of Eye)



COUNT TREES = 1 mile Off


Distance Off = 1/2 Time in seconds * .18


Distance Off = Time in Seconds * .18


You will need a calculator with Sin & Cosine functions.

D = distance
R = distance run
A = First Bearing
R = distance run
A = First Bearing
B = Second Bearing

Distance Off at Fiirst Bearing & Run Abeam:

D = (R x sin A) / Cos A

Distance Off Second Bearing Form Second Bearing on Bow & Run:

D = (R x sin A) / (sin A [abs. diff.] B)

Distance Off Abeam with Second Bearing on Bow and Run Betweeen:

D1 = (R x sin 2B) / sin C

D2 = D1 x sin A (D2 = distance off abeam)

Distance Run to a Given Bearing & Distance Off When on That Bearing:

D1 = (R1 x sin B) / sin C

D2 = D1 x sin A (D2 equals distance off abeam)



Sailing to Weather

D = (200 / sine of the angle between tacks) * sine attack angle

D = percentage of the distance to the mark.

attack angle = the angle off the wind when sailing.



Distance Off Two Landmarks or Seamarks

s / SIN LS : a /sin LA : b / sin LB

s = distance between marks
LS = angle diff between a & b
a = distance from ship to b
LA = angle diff between bearing of a from ship & bearing of b from a
b = distance from ship to a
LB = angle diff between bearing from b to a & Bearing b from ship


Tacking Downwind

Total distance sailed =

2 * base distance * sin of the divergence angle/sin (divergence angle * 2)


Contributed by Dan Hogan
West Covina, CA


Great Circle Distance between Points A and B
located as;

A at location (Lat_A, Lon_A) and B at (Lat_B, Lon_B)

Distance A to B = 60*ArcCos[Sin(Lat_A)*Sin(Lat_B) + Cos(Lat_A)*Cos(Lat_B) *

Cos(Lon_A -Lon_B)]

The result is in nautical miles.


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