Coast Piloting Part 4 – Lines of Position

This tip could have been named “Obtaining a Fix.”  Maybe it should have been, because that’s what its all about.

Dead Reckoning is a great thing.   It’s a way to figure out approximately where you are.  However, the goal of every navigator to to know exactly where they are as often as possible.  This is known as a “fix,” and you can’t obtain a fix without first establishing two or more lines of position (generally referred to as LOPs.)    There are several ways to establish an LOP, and we will be discussing a number of the more commonly used.  Especially those that don’t require specialized equipment not normally found on a small sailboat.  A sextant is a great tool, and can be used in a variety of ways to find an LOP, however, I don’t generally have one on board when I’m sailing, and I don’t recall ever having seen a pelorus on a 42 foot sailboat.  What we do have are compasses, depth sounders, and radars, so for the most part we will limit the discussion to LOPs  generated by them.

There is one very important thing to keep in mind when talking about obtaining a fix.  One LOP will never work to generate a fix.  It takes at least two, and better yet, three or more.  If everything and everyone was perfect, two bearings to different objects would provide a very precise location.  Unfortunately, perfect isn’t going to happen.  If you are looking to get bearings to an object, it’s hard to maintain closer than 5 degrees of accuracy using a hand held compass on a rolling deck, and who knows, maybe you are standing too close to something magnetic (like the hand held VHF radio in your PFD pocket).  Stuff happens.  The more redundancy you have, the less errors are going to impact you.

Bearing to an object – A compass bearing taken of two or more charted objects generally provides one of the more accurate fixes.  Using day 1 of the Tradewinds ACC class as an example, after exiting the Golden Gate, the class proceeds to the buoys marking the Main Ship Channel through the San Francisco Bar.  At G “8”, a decision needs to be made.  Continue through the buoyed channel, or turn south now.  Seas over the bar are 6  to 7 feet, with winds out of the NW at 10 to 15, so it is determined a turn south at that location would present no dangers to vessel or crew.  The turn is made at 0954 and a DR begun on C 180.  The DR projects positions at 1000, 1100, and 1200, with appropriate expansion circles (see part 1 for an explanation).  At 1100 a bearing is taken of a charted TV antenna (B 053) and San Pedro Rock (B 153).  Each bearing is marked on the chart.  The LOPs are highlighted in yellow for visibility.  The resulting fix puts the vessel .6 miles (drift) on a bearing of 109 degrees (set) from the 1100 DR position.  The DR is reset from the fix.  the navigator now has information regarding set and drift, which should be applied to the reset DR.  For additional information regarding set and drift, how to plan for it, and how to correct for it, take a look at the Skipper’s Tip entitled Coastal Pilot Part 3 – Course to Steer.

There are two commonly used hand bearing compasses.  The first is much like a pistol grip.  There is a front and a rear sight, which are lined up on the object, and the bearing is read from the compass.  The second is puck shaped and is held to the eye in use.  A prism allows both the object and the compass reading to be in focus at the same time.  Both work, however the puck shaped compass is easier to use while the pistol grip compass is less expensive.

Depth Contours – In Coast Piloting Part 2 – Entering an Unknown Port, depth contours were used to mark danger areas.  In Coast Piloting Part 1 – Dead Reckoning, a depth contour was used as a second LOP in conjunction with the bearing to a light in order to obtain a fix.  In this illustration, the 10 fathom contour is marked in read as a danger area.  You may notice that the 20 fathom contour (marked in yellow) runs nearly straight for nine miles, keeping approximately 2 miles offshore.  A vessel returning from Drakes Bay to San Francisco might sail to the 20 fathom contour and follow it south.  If the depth indicated on the depth sounder shows an increase, the helm can alter course a few degrees toward shore.  If shallower, altering course a few degrees seaward puts the vessel back on track.  As you can see, a depth contour marked on a chart can be a valuable tool.  However, you must use them with discretion.  The depth contours may not be distinct enough to be located.  The area south of the San Francisco Bar is quite flat and depth isn’t going to help much in obtaining a fix.  Also, depth surveys may be quite old and depending on location, the depths may have changed dramatically.

Running Fixes – Running fixes are second only to set and drift in creating confusion in the mind of a new navigator.  This is due in large part because of the way running fixes are described.  There are some pretty confusing statements … “Advance the LOP forward the distance traveled between bearings.”

As an example.  While traveling a Course of 180º from Drakes Bay bearing is taken of a prominent point.  The DR position at that time is marked.  For simplicity, I have labeled it “A”.  The bearing is marked off and labeled 0945 (the time the bearing was taken).  At 1015, a second bearing of the same point is taken, (it doesn’t have to be that way it can be a different object), marked off on the chart, and labeled 1015.  The DR at 1015 is plotted.  Again, for simplicity, I have labeled this DR position “B”.  The distance between DR position A and DR position B is 2.5 miles, therefore, 2.5 miles is measured from the point where bearing 0945 crosses the DR line.  A line parallel to “0945” is marked off crossing the DR line 2.5 miles from where “0945”  crosses.  This new line is labeled “0945-1015”.  The location where “1045” and “0945-1015” cross is your fix.

Distance Off – the final method of achieving an LOP we will be discussing is distance off.  Actually, its not an LOP, it is a circle of position, but works the same even though its drawn as an arc.  The easiest method I know of to obtain distance off is by using radar.  Do not go off shore in Northern California without radar.  There is too great a chance of fog and radar will be the only measure of safety you have available to you to protect from dangers you can’t see.  The concentric rings on the radar make it easy to determine distance off one the object has been identified on the radar screen.

The second method of finding distance off involves something called “angle off the bow”.  While on a vessel traveling a course of 180º, a bearing  of 150º is taken to an object.  That object is 30º off the bow.  As the vessel moves, the bearing to the object will decrease, increasing the angle off the bow.  When the bearing reads 120º, the object is 60º off the bow (double the original reading of 30º).  The distance traveled between the time of the first and second bearings is equal to the distance off from the object.

We have explored the more commonly used LOPs to result in a fix.  Using them will provide you with assurance of exactly where you are, even though you are in unfamiliar waters.  All it takes is a few tools, and some practice.

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Inland Navigation Rules – Simplified! Rules 20 through 30 – By Tradewinds Instructor Virginia L.

Inland Navigation Rules

Nav Rules Make Easy

Rules 20 to 30

In the Nav Rules Made Easy series, we’ll explain each Inland Navigation Rule, with an emphasis on the information that’s most important for recreational sailing in the San Francisco Bay.  We won’t include portions of the rules that are highly technical and intended for commercial mariners.

Note: If you travel more than one mile outside the Golden Gate Bridge or if you charter a boat in another country, the International Rules apply.  Many of the International Rules are exactly the same as the Inland Rules.  However, there are also a few that contain important and significant differences from Inland.  Make sure that you study and learn International Rules if you are traveling in international waters.

This is just a simplified summary of the rules.  To get detailed information, please refer to the Navigation Rules and Regulations Handbook from Department of Homeland Security, United States Coast Guard.

 Rule 20 – Lights and Shapes — Application

Rules 20 to 30 provide guidelines and information about navigation lights and shapes.  To put this whole section into perspective, think about driving on the freeway at night.  If you see a lot of red lights in front of you, you know that you’re coming up on traffic that is going the same direction you are traveling.  Cars have red lights at the back of the vehicle.  If you see white whites, however, you know that the cars are coming toward you.  Navigation lights for boats are more complicated than the light systems used traveling on roads.

All vessels must display proper navigation lights from sunset to sunrise and during periods of restricted visibility.

If there are any lights on the boat in addition to navigation lights, the other lights have to be arranged so that they cannot be mistaken for navigation lights.  It’s also important that no lights interfere with keeping a proper lookout.

Rules 21 and 22 – Definitions and Visibility of lights

During the day, it’s fairly easy to see what kind of boat is out on the water.  At night, however, it’s difficult.  So, the navigation rules specify different lights for each type of vessel.  That way you can tell the type of vessel by understanding the light pattern displayed.

Since we don’t operate Tradewinds boats at night, you might wonder why you should learn about navigation lights.  There are a couple of reasons.  First, you must use navigation lights in “reduced visibility” or fog.  Second, you may decide to charter a boat and find yourself on the water at night.  Of course, there’s also always the possibility that you go sailing on a friend’s boat after dark.  When you’re out on the water at night, you want to be able to understand what you are seeing.

Before learning the “identity lights”, it’s important to understand a few terms:

Look at these diagrams to see the “masthead” light, sidelights, and sternlight:

This diagram shows the yellow “towing” light above the sternlight:

Rules 23, 24, 25, 26, 27, 29, 30 – Power-driven vessels underway

(There is no Inland Rule 28)

For this section, we won’t cover all of the technical details regarding specific lighting for towing and other special situations.  To get more specific information about various tow configurations, please consult the Navigation Rules and Regulations Handbook.

All boats underway must have sidelights and a white sternlight.  For all boats, the starboard sidelight is green and the port sidelight is red.

Boats differ in the color and configuration of the masthead or all-round lights displayed.  When multiple “all-round” lights are shown, they are arranged in a vertical line.

When a boat is not underway (not making way through the water), the sidelights and sternlight are no longer displayed.  This is the case when a boat is anchored or has run aground.

During the daytime, there are specific “dayshapes” that certain vessels are required to display.

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Inland Navigation Rules – Simplified! Rule 19 – By Tradewinds Instructor Virginia L.

Inland Navigation Rules

Nav Rules Make Easy

Rule 19

In the Nav Rules Made Easy series, we’ll explain each Inland Navigation Rule, with an emphasis on the information that’s most important for recreational sailing in the San Francisco Bay.  We won’t include portions of the rules that are highly technical and intended for commercial mariners.

Note: If you travel more than one mile outside the Golden Gate Bridge or if you charter a boat in another country, the International Rules apply.  Many of the International Rules are exactly the same as the Inland Rules.  However, there are also a few that contain important and significant differences from Inland.  Make sure that you study and learn International Rules if you are traveling in international waters.

This is just a simplified summary of the rules.  To get detailed information, please refer to the Navigation Rules and Regulations Handbook from Department of Homeland Security, United States Coast Guard.


Rule 19 – Conduct of vessels in restricted visibility

Rule 19 applies when there is restricted visibility and vessels cannot see each other.  Fog and heavy rain are the most frequent causes of restricted visibility.

All vessels must be operating at a safe speed and the helmsperson must be ready to maneuver the boat quickly.  A boat is traveling at safe speed when the boat is able to safely stop in adequate time to avoid a collision.

Rule 19 reminds us that in restricted visibility, we must follow rules 5 to 10 which apply all the time:

  • Rule 5: Maintain a lookout
  • Rule 6: Operate the boat at a safe speed
  • Rule 7: Be aware of all other boats and objects on the water. If any possibility of collision exists, assume there is risk.  Use all equipment available (radar, binoculars) to figure out if there is risk of collision.
  • Rule 8: Avoid collisions. When your boat is the “give-way” vessel, make a large enough course change to clearly communicate to the other boat that you are changing course.  Make your course change sooner, rather than later.  Give the other boat plenty of room.  In close quarters where a course change is not possible, slow down … go to neutral or even reverse to avoid any possibility of a collision.  Make sure that you maintain “rudder authority” – the ability to steer the boat.  Don’t go so slow that you can’t steer!
  • Rule 9: Understand the definition of “narrow channel”.  Know when you are in a narrow channel.  When you are in a narrow channel, stay as far to the starboard side as possible.  Do not get in the way of vessels that can only operate in the channel.  Give way to barges, tugs, car carriers, cargo ships, and tankers.
  • Rule 10: Understand that Traffic Separation Schemes exist and contain lanes for traffic going in one direction or another.  The schemes include an area between traffic lanes that acts like a median on the freeway – the “separation zone” keeps apart traffic going in opposite directions.

Know when you are in a Traffic Separation Scheme.  When you are, go with the flow of traffic.  Stay out of the Separation Zone.  Merge into traffic in traffic lanes with as little angle as possible to the direction of travel.  Cross traffic lanes at a 90 degree angle.

If you are using radar and see another vessel on the radar screen, decide if there is any risk of collision.  If there is risk of collision, take action as soon as possible to alter course.

If the other vessel is detected forward of your beam, do not alter your course to port.

No matter where the other vessel is detected, do not alter course toward the other boat.

If you hear a fog signal from another vessel forward of your beam, reduce your speed to “bare steerageway”.  Continue navigating with great caution until any risk of collision is gone.

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Inland Navigation Rules – Simplified! 11 through 18 – By Tradewinds Instructor Virginia L.

Inland Navigation Rules

Nav Rules Made Easy

Rules 11 to 18

In the Nav Rules Made Easy series, we’ll explain each Inland Navigation Rule, with an emphasis on the information that’s most important for recreational sailing in the San Francisco Bay.  We won’t include portions of the rules that are highly technical and intended for commercial mariners.

Note: If you travel more than one mile outside the Golden Gate Bridge or if you charter a boat in another country, the International Rules apply.  Many of the International Rules are exactly the same as the Inland Rules.  However, there are also a few that contain important and significant differences from Inland.  Make sure that you study and learn International Rules if you are traveling in international waters.

This is just a simplified summary of the rules.  To get detailed information, please refer to the

Navigation Rules and Regulations Handbook from Department of Homeland Security, United States Coast Guard.

 Rule 11 – Application

Rules 12 to 18 apply when boats on the water are able to see each other.

 Rule 12 – Sailing vessels

When two sailboats are at risk of collision, there are rules to clarify which boat gives way.

  • If one sailboat is on starboard tack and the other one is on port tack, the port tack boat gives way to the boat on starboard tack.

    The boat with the wind on the starboard side is the “stand on” vessel.  The boat with the wind on the port side must stay out of the way of the starboard tack boat.

  • If two sailboats are both on the same tack (does not matter whether that is starboard or port), the upwind boat gives way to the boat downwind. The upwind boat is called the “windward” vessel, and the downwind boat is the “leeward” vessel.
  • If you are sailing on port tack and can’t figure out if the other boat is on port or starboard tack, assume they are on starboard tack and stay out of the way.
  • A sailboat is on starboard tack when the mainsail is on the port side. The boat is on port tack when the main is on the starboard side. 

Rule 13 – Overtaking

If you are overtaking or passing another boat, you must stay clear of the boat being overtaken.  Your boat is the “give-way” boat, and the overtaken boat is the “stand-on” boat.

If you are under sail and overtake a power boat, you are the “give-way” vessel, and the power boat is the “stand-on” vessel.

If you’re not sure whether you are overtaking another boat, assume that you are overtaking and give way to the other boat.

Continue to give way until you are well past the other boat.

Rule 14 – Head-on situation

This rule applies to power boats.

Note:  If you are on a sailboat using engine power, you are a power boat.

If two power boats are on course to meet head-on, each boat alters course to starboard so that the boats pass port side to port side.

If you’re not sure if you’re going to meet head-on, assume that you will be meeting and alter course to starboard.

Rule 15 – Crossing situation

This rule applies to power boats.

When two power boats are crossing and there is risk of collision, the boat on the port side gives way to the boat on the starboard side.  The boat on the starboard side is the stand-on vessel.

The give-way boat should not cross in front of the stand-on boat.  

Rule 16 – Action by give-way vessel

When your boat is the “give-way” vessel, you are required to change course or speed to avoid a collision.

Make course changes obvious enough so the other vessel can clearly see that you are altering course to avoid them, and soon enough to avoid the other boat’s skipper getting nervous.

Rule 17 – Action by stand-on vessel

When your boat is the “stand-on” vessel, maintain your course and speed.  By maintaining your course and speed, you become predictable for the “give-way” vessel.  The give-way vessel moves to get out of the way based on your position.

If you are the “stand-on” vessel and the “give-way” vessel does not change course or speed to get out of your way, then you immediately change course or speed to avoid a collision.

Rule 18 – Responsibilities between vessels

The navigation rules provides a clearly defined structure to follow regarding the various types of vessels and who gives way.  In this structure, it’s important to understand the meaning of “Vessels Restricted in their Ability to Maneuver”.  This is a technical definition.  It means that the boat is actively engaged in work that results in limited maneuverability.  Here are a few examples:

  • A buoy tender working on a buoy
  • A pilot boat transferring a pilot to another vessel
  • A boat towing another boat and the tow arrangement makes maneuverability difficult

It is also important to understand the term: “Vessel Not Under Command”.  A vessel not under command is a boat or water craft that can’t be steered and cannot get out of the way of another boat.

Hierarchy of vessels:

On open water when vessels can see each other, and there is not an “overtaking” situation, here is the order we follow:

  • Seaplanes give way to all other vessels
  • Power driven boats give way to all vessels except seaplanes
  • Sailboats give way to
    • Fishing boat actively fishing with lines and nets out
    • Vessels restricted in their ability to maneuver
    • Vessels not under command
  • Fishing boats actively fishing give way to
    • Vessels restricted in their ability to maneuver
    • Vessels not under command
  • Vessels restricted in their ability to maneuver give way to
    • Vessels not under command

To help understand the arrangement of who gives way to whom, please review this diagram:

The “hierarchy of vessels” is an important concept to master if you’re going to be out on the water.

Here it is again in a more simplified version:

Not Under Command

Restricted in Ability to Maneuver





Here’s a mnemonic to help you remember the order of vessels:

Nutty Not Under Command
Rabbits Restricted in Ability to Maneuver
From Fishing
Space Sailing
Prefer Power
Strawberries Seaplanes

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Inland Navigation Rules – Simplified! 7 through 10 – By Tradewinds Instructor Virginia L.

Inland Navigation Rules

Nav Rules Make Easy

Rules 7 – 8 – 9 – 10

In the Nav Rules Made Easy series, we’ll explain each Inland Navigation Rule, with an emphasis on the information that’s most important for recreational sailing in the San Francisco Bay.  We won’t include portions of the rules that are highly technical and intended for commercial mariners.

Note: If you travel more than one mile outside the Golden Gate Bridge or if you charter a boat in another country, the International Rules apply.  Many of the International Rules are exactly the same as the Inland Rules.  However, there are also a few that contain important and significant differences from Inland.  Make sure that you study and learn International Rules if you are traveling in international waters.

 Rule 7 – Risk of collision

Rule #7 tells us to avoid any possibility of hitting another boat or obstacle.

Maintain awareness of your surroundings.  Make sure that you can see 360 degrees around your boat.

Use all the tools and equipment available to help you be fully aware of other boats and objects on the water.

Use binoculars, sunglasses, radar, boat tracking software applications, chart plotters and nautical charts to help you see other boats.

Be aware of other boats on the water and decide if there is any risk of collision.  If you think there is any possible risk of collision, assume that there is risk and then take appropriate action.

Let’s consider a few examples.

What if the lookout sees an image on radar that is not clear and wonders if the image could be another vessel or object on the water?  In this case, the rules tell the lookout to assume that the image is another vessel or object, and to avoid that area.

What if you’re out on the water and there is a lot of sun glare making it hard to see?  Make sure that you have sunglasses that block sun glare so you can see other boats.  If you see something and you’re not sure if it’s another boat, Rule 7 tells you to assume that it is a boat.

Rule 7 also talks about the concept of “constant bearing, decreasing range.”  This means that another boat stays in the same relative position to your boat as the boats become closer to each other.  If the position stays the same as the boats get closer, there is definite collision risk.

What if you see another boat on the water and the boat’s position stays the same relative to your boat?  Let’s say you see a boat coming from your starboard side at ten o’clock.  Ten minutes later, the boat is still at ten o’clock relative to your boat.  Since the other boat’s position did not change, your boat and the other boat are on a collision course.

There are some situations when the other boat’s relative position will actually change and yet you are still on a collision course.  This can happen if the other boat is very large, like a barge.  It can also happen if the other boat is very close to your boat.

  Rule 8 – Action to avoid collision

When your boat is the “give-way” vessel, you are required to change course or speed to avoid a collision.

Make course changes obvious enough so the other vessel can clearly see that you are altering course to avoid them, and soon enough to avoid the other boat’s skipper getting nervous.

There are some standard, recommended course changes to make when you are the “give-way” vessel:

  • If you are under power and avoiding another power boat in a crossing situation, steer toward the stern of the other boat
  • If you are under power going toward another power boat head-on, steer to starboard and pass the other boat on your port side
  • If you are sailing on port tack and the other boat is sailing starboard tack, steer toward the other boat’s stern
  • If you are sailing on the same tack as the other boat and you are upwind (the windward vessel), steer toward the stern of the other boat

The key point in this rule is to make a big enough course change so that it is obvious to the other boat.  Make course change sooner, rather than later.  Make the change before the other skipper gets nervous.

When you change course to avoid collision, keep a safe distance from the other boat.  Don’t go too close!

After making your course change, wait until the other vessel is far enough away that there is no possible risk of collision.  Once you are fully clear of the other boat, resume the course you were on before your course change.  Sometimes, the situation requires you to reduce speed rather than make a course change.  This can happen in close-quarters  situations.  Do all you can to make a significant reduction in speed, even if it means using reverse to help slow your boat.

Rule 9 – Narrow channels

First of all, what’s a “narrow channel”?  The term “narrow channel” is defined by the vessels in the channel.  You are in a “narrow channel” if there are any vessels that are restricted to staying within the channel because of depth or obstructions.

A good example is Potrero Reach.  As you know, the large commercial barges, tugs, and tankers must stay within the channel or risk going aground.  So, Potrero Reach is a “narrow channel”  It continues to be a “narrow channel” all the way under the Richmond/San Rafael Bridge and into San Pablo Bay.  When you sail in the Potrero Reach shipping channel, you are in a “narrow channel”.

Now that you know the definition of “narrow channel”, look at the chart of San Francisco  Bay.  Look at all of the shipping channels!

When you are in a “narrow channel”, there are specific rules that apply:

  • Stay as far to the starboard side of the channel as possible.
  • Do not get in the way of vessels that can only operate in the narrow channel. Stay out of the way of tankers, car carriers, container ships, tugs, and barges.
  • Do not cross the channel if your boat will get in the way of boats restricted to the channel.
  • Do not anchor in the channel.
  • If you come to a blind corner in the channel, use a sound signal of one prolonged blast before going around the corner. One prolonged blast is a horn sound for 4-6 seconds.
  • If you are overtaking another vessel, remember that you are the “give-way” boat, even if you are under sail! The vessel being overtaken is the “stand-on” boat.  Stay out of their way.


Rule 10 – Traffic separation schemes

In the busiest commercial shipping areas, there are designated traffic systems, called schemes.  Within traffic schemes, there are lanes designated for traffic to flow in one direction or another.  Generally, there are eastbound and westbound lanes or northbound and southbound lanes.  It’s just like the way a freeway is designed.  One lane goes one way and the opposite lane goes the opposite way.  In between the two lanes, there is a “separation zone” which is just like the median on a freeway.  The separation zone keeps ships going in opposite directions apart.

Look at the nautical chart and note the arrows in the shipping lanes.  The arrows show you the traffic flow.  Find the wide magenta-colored lines.  These are the separation zones at the entrance to San Francisco Bay.

There are specific rules about boat traffic in separation schemes:

  • Use the traffic lane that is designed for the direction you want to travel. Use the eastbound lane when you are traveling east and the westbound lane when you are traveling west.
  • Stay out of the separation zone unless there is an emergency and you have to use the separation zone to avoid danger.
  • You can use the separation zone to fish.
  • When merging into a traffic lane, merge with as little angle to the lane as possible. This is similar to getting on a freeway using the onramp.
  • Avoid crossing traffic lanes. If you have to cross traffic lanes, cross at a 90 degree angle to the lane and the traffic flow
  • Do not anchor in any traffic lanes or in the separation zone
  • Be extremely careful when you are in the area at the end of a traffic scheme.
  • If you are not using the traffic scheme, avoid the area. If you are not using the traffic lanes, stay clear of the area.
  • If you are fishing, you must give way to all other boats.
  • If you are sailing, you must give way to all boats who are in the traffic lanes going with the flow of traffic – that includes power boats.

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Inland Navigation Rules – Simplified! 1 through 6 – By Tradewinds Instructor Virginia L.

Inland Navigation Rules

Nav Rules Made Easy

The Navigation Rules are also commonly called “rules of the road” and apply to you, me and all Tradewinds skippers.

The rules are nicknamed, “Colregs” which stands for International Regulations for Preventing Collisions at Sea.

Let’s stop for a minute and think about that.

The purpose of the rules is to prevent boats from getting in accidents with other boats on the water.

Why?  Why is so important to prevent boating accidents?

It’s important to prevent collisions because boating accidents can be much more serious than accidents on land.

Think about it.

If a boat gets into a “fender bender” with another boat, it’s possible that the damage, even if the damage is “just a small hole in the hull” can quickly cause a dangerous and even life-threatening situation.

If a boat gets into an accident on the water, the boat can’t just pull over to the side of the road.  There is no “side of the road”.

So, the Navigation Rules, or “Colregs” is a set of rules that tell us how to interact with other boats on the water.  The purpose of the rules is to ensure that everyone does everything possible to avoid a boating collision.  The rules apply to almost anything that floats with at least one passenger.

In this Nav Rules Made Easy series, we’ll explain each Inland Navigation Rule, with an emphasis on the information that’s most important for recreational sailing in the San Francisco Bay.  We won’t include portions of the rules that are highly technical and intended for commercial mariners.

Note: If you travel more than one mile outside the Golden Gate Bridge or if you charter a boat in another country, the International Rules apply.  Many of the International Rules are exactly the same as the Inland Rules.  However, there are also a few that contain important and significant differences from Inland.  Make sure that you study and learn International Rules if you are traveling in international waters.

 Rule 1 – Application

Rule #1 tells us when the Nav Rules apply.  To figure out if the Nav Rules apply to your boat or watercraft, just answer these few questions:

  • Does it float?
  • Is it intended to have at least one passenger?

If the answer to both of these questions is “yes”, then the Nav Rules apply.

The Nav Rules apply to almost anything that floats and was designed for at least one passenger.  That means that Nav Rules apply to all boats, ships, yachts, seaplanes, kayaks, dinghys, paddleboards, etc.


Rule 2 – Responsibility

Rule #2 tells us that there is no excuse for not knowing and following the rules.

If you don’t follow the rules, you are completely responsible for any and all consequences of your actions.

No excuses accepted.  None.

As skipper, boat owner, and/or crew, you are expected to know:

  • the limitations of the boat you’re driving
  • the limitations of other boats on the water
  • any hazardous areas where you are sailing (too shallow, lee shore, etc.)
  • when to break a rule in order to avoid a collision

 Rule 3 – General definitions

Some of the terms used in the Navigation Rules are very precise.  To understand the rules, you have to understand the definitions of certain words.  Here are some of the words defined in Rule 3.

Vessel – anything that floats and was designed to carry at least one person.  A vessel is anything used for transportation on the water.

Power-driven vessel – any water craft with an engine or motor that is powering it through the water (a sailboat is a power-driven vessel when the engine is being used).

Sailing vessel – any water craft that is powered by sails and the sails are being used to power the boat.  If the boat has an engine or motor, the engine or motor is off.

Vessel engaged in fishing – a boat with nets, lines, trawls or other fishing gear that is in use.  The fishing gear makes the boat difficult to maneuver.  This definition doesn’t include boats with trolling lines.  Trolling lines are fishing lines that trail behind the boat while the boat is underway.  Trawling is fishing by pulling a net through the water behind the boat.

Seaplane – a plane that is moving around on the water.

Vessel not under command – a boat or water craft that can’t be steered and cannot get out of the way of another boat.

Vessel restricted in her ability to maneuver – a boat doing work that results in the boat not being able to maneuver freely.  Here are some examples:

  • a buoy tender picking up or fixing a buoy or daymark
  • a barge dredging
  • a pilot boat transferring a pilot to a cargo ship
  • an aircraft carrier when planes are taking off or landing
  • a boat towing another boat and the tow boat is not able to maneuver easily

Underway – when a boat is on the water and not attached to anything.  The boat is not anchored.  The boat is not tied to a dock or mooring ball.  A boat is underway even if the engine is off or the sails are down.

Length – the total length of the boat from stern to bow

Breadth – the widest part of the boat (beam)

Vessels in sight of each other – when one boat can visually see another boat

Restricted visibility – any type of condition that makes visibility difficult.  This can mean fog, rain, mist, etc.

Rule 4 – Application

Rule #4 says that rules 5, 6, 7, 8, 9 and 10 apply all during all types of visibility.  If the weather is clear and visibility is good, the rules apply.  If there is fog, mist or rain and visibility is poor, the rules apply.

Rule 5 – Look-out

Every vessel on the water must always have at least one person who is designated as look-out.  The look-out is expected to look and listen for other boats, objects or obstacles.  Skipper and crew on the boat must use all tools available to assist with being an effective look-out.  Look-out tools include radar and binoculars.  The look-out not only needs to be able to see and hear boats and obstacles, the look-out also needs to be able to have the time and attention to determine if any risks exist.  If there are risks or hazards, the look-out needs to be able to have a full understanding of the situation.  In other words, the look-out should not be doing anything else when assigned to look-out duty.

 Rule 6 – Safe speed

Every boat on the water must always maintain a safe speed. A boat is traveling at safe speed when the boat is able to safely stop in adequate time to avoid a collision.

Here are the factors to consider when trying to determine “safe speed”:

  • Visibility – is it foggy? Are you able to see?  Is there sun glare?
  • Other boat traffic – are there lots of other boats around?
  • Maneuverability – are you able to stop the boat? Can you make a quick turn?
  • At night, are there lights from shore that make it hard to see what’s happening on the water?
  • Are there navigational hazards nearby? Are there shoals?  Jetties?
  • Environment – is it windy? Is there strong current?  Are there swells or choppy seas?
  • What is the water depth? Is there plenty of clearance under the keel?  Are you concerned about running aground?

If the boat has radar:

  • Do you know how to use radar?
  • What are the limitations of the radar equipment?
  • Is there scatter from waves, weather or anything else?
  • Are you reminding yourself that radar won’t “see” small boats or debris in the water?
  • Do you know how to read the radar screen to determine movement of other boats?

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Coast Piloting Part 3 – Course to Steer

If ever there was a “catch all” navigation tip, this is it.  While determining a course to steer, the navigator needs to know and/or take into consideration:

  • The relationship of Distance, Speed, and Time
  • Conversion from True to Magnetic to Course to Steer
  • Set and Drift, and their impact on the course steered
  • How to correct a course to arrive at a specific destination
  • Estimated position

All of which adds up to a feeling that if it isn’t talked about elsewhere, lets talk about it here.

The Relationship of Distance, Speed, and Time – If any two are known, the third can be easily calculated using simple multiplication and division.  The “D ST Triangle” to the right provides a great representation of the relationship of calculating distance, speed, and time.

When using the triangle as an aid, D is always in nautical miles (e.g. 5.5 nm), S is always in knots (e.g. 6 kts), and time is always in hours (never minutes or hours and minutes).  90 minutes is not 1:30.  90 minutes would be represented as 1.5 hours.  When doing D ST calculations, values to the nearest 1/10 generally provide sufficient accuracy for the coastal pilot.  In use, visualize the horizontal line under D as a division sign, and the vertical line between S and T as a multiplication sign.

As can be seen in the examples, if give tenths of a hour, multiply the tenths by 60 to come up with minutes.  If given minutes, divide the minutes by 60 to find tenths.  If you can’t remember whether to multiply or divide, just pick one.  If the answer doesn’t look right, do the other.

Conversion from True to Magnetic to Course to Steer – When converting directions, the TVMDC table shown here is invaluable.  Conversions will become second nature, however, when first starting out, I recommend duplicating the table on a pad and using it to fill in and calculate direction.

  • T = direction in degrees relative to true north.
  • V = variation, taken from the center of the compass rose on the chart of the area you are sailing is the difference between true and magnetic north, and is stated as degrees west or east (e.g. 14E indicates magnetic north is points 14 degrees to the east of true north.
  • M= direction in degrees relative to magnetic north.  Degrees true, plus or minus variation, equals degrees Magnetic.
  • D = deviation is specific to the vessel and compass being used.  Because of magnetic influences on the vessel, no compass can be adjusted to be perfectly accurate.  Instead, adjustment gets it as close as possible, and a record, called a deviation card or a compass card, is kept of the differences.  Deviation will vary at each heading, so the card records the difference at set intervals around the compass, generally 22.5 degrees apart.  Deviation in between the provided headings can easily be estimated.  055º is approximately half way between 045º and 067.5º, therefor deviation would be 1ºE.
  • C = ship’s compass (known as PSC or per ship’s compass)

All of this seems quite complex, however, if the TVMDC table is drawn and used, it all becomes very simple.  The course over ground from just north of Southeast Farallon Island to the entrance to Drakes Bay is “C 012”.  Variation according to the compass rose is 14E, which is subtracted to get “C 358 M”.  Deviation of 4W is added to get a course to steer of “C 002 PSC).  All that’s left to arrive at Drakes Bay safely is to account for wind, current, helm error, typically grouped together as set and drift.

Set and Drift – technically, set and drift are limited to the impact on a vessel of the direction and speed of current in the area the vessel is passing through.  Unfortunately, while underway current is nearly impossible to separate from the effects of leeway (wind) and helm error.  Instead, all are typically lumped together as “set and drift” to show the net result.  Set is direction and drift is speed.

Back to our example of a Tradewinds Advanced Coastal Cruising class.  On day one, the vessel is piloted out to G “8” of the Main Ship Channel through the San Francisco Bar.  At 0954 a turn to the south is executed.  The desired course over ground is “C 180”.  Applying variation of 14E results in “C 166 M”.  5E of deviation at 157.5º per the chart above is used, resulting in a course to steer of “C 161 PSC”.  DR positions are plotted for 1000, 1100, and 1200.  At 1100, a fix was obtained (see Part 4 to follow) and it was determined the vessel is .6 miles away from the expected DR position, in a direction of 110º.  Set therefore is 110º.  Drift will require further work, because the .6 miles is over 1 hour and 6 minutes, not over 1 hour as required.  Using the D ST triangle, distance is .6 divided by 1.1 hours equals 0.545, so set is approximately 0.5 knots.  You can also find a DR 1 hour from the DR start time of 0954, draw and measure the set.

How to correct a course to arrive at a specific destination – A new course line can now be drawn from the fix location to the location of the next turn.  The new course to the next turn point is C 184.  However, if you steer that course, you will end up .5 miles of target due to set and drift.  To correct for set and drift, continue the set line thru the fix location for a distance equal to the drift.  In this case, 0.5 miles.  Draw a line from that point, to the DR location 1 hour later.  The course line to correct for set and drift is 189º, and should be relayed to the helm as “C 171 PSC”.  Steering that course should result in a course made good of 184º, allowing you to reach the next turn at approximately 1250.

Estimated position – every skippers tip should have a bit of controversy in it, right?  If so, here it is.  The term “estimated position” is used differently by different authors and publications.  One such usage involves estimating a position based on a DR position and a single line of position (LOP), like a bearing to a charted object.  The process involves drawing a line that runs perpendicular to the LOP, running through the DR position.  The estimated position is the point the perpendicular line crosses the LOP.  Sadly, I have had times where the error in this estimate was unacceptable.  On one occasion, I was able to get a fix by using a bearing and the depth.  I was  1.3 miles of of the Farallons, but an EP calculated at the same time had me 2.1 miles out, simply because I was travelling .2 kts faster than my DR indicated.  Others will argue, however, I don’t recommend the use of estimated position in that manner unless there is no other choice.  Neither does The American Practical Navigator as it isn’t even in the book.

Instead, an estimated position is correcting a DR plot for known set and drift.  In the above example, if I consistently have a set and drift of 110º/0.5 heading south from buoy G “8”, then it would make sense to note it as part of my DR during later voyages.  You will note in the illustration I did not reset my DR to the EP.  Instead, I just noted it, and would include the information in developing my DR expansion circles.  The DR should only be reset with a fix or a running fix.

I hope you stuck with me this far.  If so, you will be happy to know that I my opinion, you have survived the most challenging part of coastal piloting.

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Coast Piloting Part 2 – Entering an Unknown Port

When I think of Bareboat Cruising students and graduates, I visualize a skipper interested in spending a week or two on a chartered boat, enjoying an established cruising area with an number of “day sails,” stopping nightly to dock, moor, or anchor in places of interest.  Advanced Coastal Cruising on the other hand involves moving a vessel from point A to point B, involving distances of 100 to 1000 (or more) miles, generally staying within 100 miles of shore, sailing by day and by night as required, and only stopping when indicated by the needs of the crew and/or vessel.

One thing required during both types of sailing adventures is the probability of entering a port previously unknown to the skipper.  Unknown ports can be found as close to home as Pillar Point Harbor 20 miles south of San Francisco,  or in a different country, such as the port in La Paz,  Baja California Sur, Mexico.  Regardless of where it is found, an unknown port must be treated with the utmost respect.  This tip looks at the “pre-cruise” planning involved in piloting into a new harbor safely.

Planning for port entry starts with obtaining publications and charts covering the area.  In this example, we will be looking at entry into Pillar Point Harbor.  Publications that might be used include a number of private cruising guides, and Chapter 6 of the NOAA publication Coast Pilot 7.  Charts that might be needed include Gulf of the Farallones (18645) and Half Moon Bay (18682).

Chapter 6 of Coast Pilot 7 includes this information regarding Pillar Point Harbor:

(280) Pillar Point 18 miles south of San Francisco entrance, is the south extremity of a 2.5-mile low ridge. Several black rocks extend over 300-yards south of the point; from north these appear as three or four, but from south as only one. Half Moon Bay comprises the bight from Miramontes Point on the south to Pillar Point on the north.
(281) Pillar Point Harbor in the north part of Half Moon Bay east of Pillar Point, is used by fishing vessels and pleasure craft. The harbor is well protected by breakwaters. The entrance, 200-yards wide, is between the east and west breakwaters. A light marks the end of the east breakwater, and a light and sound signal are on the end of the west breakwater. The entrance has a depth of about 20 feet with depths of 2 to 17 feet inside the harbor. Shoaling has been reported along north side of the breakwaters inside the harbor. The harbor provides good holding ground for anchored and moored vessels. Two breakwaters and a detached breakwater, protect a marina on the north side of the harbor. The detached breakwater is marked by lights on the east and west ends.
(282) Prominent features
(283) Several buildings and a white radar antenna at the U.S. Air Force radar site about 0.2 mile north of Pillar Point are conspicuous when approaching the harbor. The lights of the radar site are conspicuous at night. A rotating aero beacon located 1 mile northwest of the marina is visible from the south.
(284) Caution is necessary in approaching Pillar Point Harbor because of the foul ground off the entrance. Rocks and reefs, marked by kelp and a lighted bell buoy, extend southeast for over 1 mile from Pillar Point. Southeast Reef extending from 1.5 to over 2 miles southeast of Pillar Point, is covered 4 to 20 feet and has a pinnacle rock awash at extreme low water at the southeast end. Mariners are advised to exercise caution in the vicinity of Pillar Point in dense fog.
(285) COLREGS Demarcation Lines
(286) The lines established for Pillar Point Harbor are described in 33 CFR 80.1140 chapter 2.
(287) Routes
(288) Vessels from the south approach the harbor east of the lighted gong buoy marking Southeast Reef; vessels from the north use the buoyed opening between the Pillar Point foul ground and Southeast Reef.

This entire excerpt includes valuable information, such as prominent features to be used as navigational aids, and information about the marina itself.  However, for this tip, we will be looking at the information in section 284 (in red) and 288 (in green).

Section 284 indicates there are two reefs to be concerned about, and Section 288 indicates approach routes for vessels entering from the north or the south.  As we will be arriving from San Francisco in our example, we will be focusing on the approach from the north, going between the two reefs.  Chart 18682 provides the best view of the approach into the harbor through these two prominent dangers.

  1. Once you have the proper chart in hand, begin by selecting a contour line you do not want to cross over and mark it conspicuously.  In this case, the 30 foot contour line seemed to be the best to avoid danger from the reef, and was highlighted using a red marker.
  2. On the trip south from San Francisco, navigation has been conducted using chart 18645.  Pick a point that would be a logical location to switch from chart 18645 over to the harbor chart.  If provided, a red and white safe water buoy is nearly always the best location to begin an approach to an unknown harbor.  If there is no approach buoy, consult the Coast Pilot, Sailing Direction Enroute, and/or cruising guides for the best location to approach from.
  3. Lay out a course line into the harbor.  As you can see, a DR course line has been established beginning at a point just north of the Pillar Point approach buoy [RW “PP” Mo (A)].   The course follows a heading of 073, for 1.6 miles.  At an estimated speed of 5 knots, 073 will be steered for  just under 20 minutes.  Note that the plotted course crosses over the 30 foot contour line that was marked, however, the chart indicates 25 plus feet of water and only for a short period of time, which won’t present a problem in this case.  A turn to C 353 is make just past the green bouy marked on the chart as G “3” Fl G 4s BELL and is followed for .8 miles (9.6 minutes) to the entrance between the breakwaters.
  4. Once the course line is plot, see if there are any danger bearings that can be located and plotted.  During the first leg, there is one danger bearing north of and one south of the planned course.   Draw a line from buoy G “1” to buoy G “3”, which bears 089 M.  Magnetic was used for the danger bearing because most likely a hand held magnetic compass would be used to take the bearing, and this simplifies comparison.  The line is labeled “NMT 089 M” meaning that any bearing taken that is greater than 089 M indicates danger.  To be safe, a second danger bearing is established on buoy R”2″.  Any bearing less than 075 M indicates you are too far south, and may be in danger of the reef.  Once the turn to the second leg is made, a new danger bearing of “NMT 338 M” presents itself, guiding you safely to the east of the breakwater light.  It is interesting to note that at night, the light itself is not visible if you are west of the line from G “3” to the light , providing a second, very obvious indication your danger bearing has been crossed.

The point of all this planning is to make you aware of any dangers, and set you on the proper course(s) to avoid them and reach your destination safely.  When done ahead of time, it only takes a few minutes, and may save you from disaster.  During one ACC class,  while exiting Pillar Point in fog, the helmsperson lost track of the compass course not long after making the turn around G “3”, and turned too far north.  After the turn was made, a quick check of the bearing to G”3″ indicated a bearing greater than 089 M and we were able to alter course before the reef came into play.  Some might call it lucky.  Others might say it is a bit paranoid to do “all that extra work” because with all the modern devices, what could possibly happen.  Personally, I credit that extra effort with saving a vessel that day … and as for the crew, who knows what would have happened if the reef had been hit?

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Exiting Chrysopylae … “The Golden Gate”

Also known as … is it safe to head out the gate?

For over two hundred years, the Golden Gate hid its existence from the Europeans transiting and exploring the coast of California by boat.  First “missed” by Juan Rodriguez Cabrillo in November 1542, the Golden Gate was discovered accidentally in November of 1769 by a land expedition working it’s way north along the San Francisco peninsula in an attempt to reach Point Reyes.  Needless to say, the one to two mile wide expanse of water moving into and out of what would become known as San Francisco Bay halted the successful completion of the mission.

In 1846, John C Freemont coined the name we now know.  In his memoirs he wrote “To this Gate I gave the name of ‘Chrysopylae’, or ‘Golden Gate’; for the same reasons that the harbor of Byzantium was called Chrysoceras, or Golden Horn.”  Freemont saw this as a “golden gate to trade with the orient.”  So, the name has nothing to do with the discovery of gold in California, or the famous bridge that spans its eastern end.

However, this is a sailing tip, not a history lesson or a linguistic exploration of the Greek word Chrysopylae, translated “Golden Gate.”  Instead, we will be looking at guidelines to follow while determining if and when it is safe to transit the Golden Gate, pass outside the line of demarcation, cross the San Francisco Bar, and sail the waters of the Gulf of the Farallons.  It is important to remember, these are guidelines which do not take into consideration your level of skill, the skill of your crew, or the seaworthiness of your vessel, all things that MUST be taken into consideration when sailing anywhere, anytime.

Gulf of the Farallones – Chart 19645


Water from the Pacific Ocean flows into (floods) and out of (ebbs) on a cycle that repeats itself twice each day.  In between each flood and ebb is a transition period referred to as slack water where there is relatively little movement of water.  Step one of deciding if it is safe to sail outside the gate is determining the best time to transit the gate.  To the untrained, the best time would seem to be during the ebb, so that you can ride the current out and get there quicker.  Unfortunately, that is actually the worst time to go.

One of the first things someone notices when approaching the bridge from the bay is that the water begins to “feel” different.  Less and less are you experiencing the wind driven waves and chop of the bay, and more and more you beginning to ride the swell coming in from the Pacific Ocean.  During an ebb, water moving out of the bay at velocities that can exceed 6 knots runs into swell coming into the bay resulting in increases in size and frequency.   A fact that is true of every river bar in the world.  Throw in San Francisco’s famous 25 knot winds and things get really interesting.

Instead, I prefer transiting the gate, in either direction, on the slack before the flood.  Second choice would be slack before the ebb, but get there a bit early.  You don’t want to get caught in transit during the ebb.  The flood would be next (makes for a slow trip out or a quick trip in) with the ebb being last.  If you must exit on an ebb, make it early in the morning before those breezes pick up.  Better yet, wait a few hours and go out on the next slack.  In the example shown, I would most likely leave Marina Bay about 10:30 to arrive at the bridge between 12:00 and 12:30.

Forecasts of the currents through the gate are found in tide books and online.,+California+Current

San Francisco Bar and Main Ship Channel

Coast Pilot 7, Chapter 7, contains a wealth of information about transiting the gate and crossing the bar.  The Coast Pilot Index if found at
Click on California to bring up Coast Pilot 7.  Unless otherwise indicated, all references to the Coast Pilot are from Coast Pilot 7, Chapter 7 (CP 7:7).

CP 7:7 Item 43, describes the San Francisco Bar as:

“a semicircular shoal with depths less than 36 feet, is formed by silt deposits carried to the ocean by the Sacramento and San Joaquin River systems. The bar extends from 3 miles south of Point Lobos to within 0.5 mile of Point Bonita off the southern coast of Marin Peninsula; the extreme outer part is about 5 miles west-southwest of San Francisco Bay entrance. Potatopatch Shoal the north part of the bar on Fourfathom Bank has depths from 24 to 28 feet.”

The San Francisco Bar is the light blue areas of shallow water shown in the excerpt from the Entrance to San Francisco Bay chart above.  It is approximately 8 miles from the bridge to the last buoy through the Main Ship Channel (G “1” Iso G 6s BELL).  Expect it to take 2 hours (plus or minus) to transit the gate and cross the bar.

CP 7:7 Item 45 and 46 contain a warning:

Very dangerous conditions develop over the bar whenever large swells, generated by storms far out at sea, reach the coast. A natural condition called shoaling causes the large swells to be amplified and increase in height when they move over the shallow water shoals. This piling up of the water over the shoals is worsened during times when the tidal current is flowing out (ebbing) through the Golden Gate. Outbound tidal current is strongest about 4 hours after high water at the Golden Gate Bridge and attains a velocity in excess of 6 knots at times. The incoming large swells are met by outbound tidal current causing very rough and dangerous conditions over the bar. Steep waves to 20 or 25 feet have been reported in the area. Mariners should exercise extreme caution as the bar conditions may change considerably in a relatively short period of time.

The most dangerous part of the San Francisco Bar is considered to be Fourfathom Bank. Bonita Channel, between the shoal and the Marin coast, can also become very dangerous during large swell conditions. The safest part of the bar is the Main Ship Channel through the center of the bar. But even that area can be extremely dangerous when the tidal current is ebbing.

CP 7:7 Items 149 through 152 discuss currents in the area.  In essence, the ebb goes straight out, and begins to fan as it goes across the bar.  However, the main strength of the current runs parallel to the south edge of Potatopatch Shoal, and through the Main Ship channel.  The flood runs straight in, with a slight set to the north shore.  Heavy rips and overfalls can be found at each of the four corners of the Golden Gate (Lime Point at the north tower of the bridge, Fort Point and the south end of the bridge, Point Lobos near Mile Rocks, and Pt Bonita to the northwest)   Overfalls at Point Bonita can extend 1/4 mile south into the strait. Eddys, rips, and overfalls can be extreme near the south tower of the bridge, and can cause even large ships to veer off course.

Once through the gate, crossing the bar through the Main Ship Channel is generally safest.

A  forecast of conditions across the bar and through the Main Ship Channel is at:

Point 1 on safety out the gate:  Time your exit to minimize the impact of dangerous currents.  Generally, the slack before flood is best.

Channels across the San Francisco Bar

There are two channels across the San Francisco Bar.

  • The Main Ship Channel
  • Bonita Channel

If you are headed north, the buoyed Bonita Channel (about 1/3 mile wide), which proceeds north after passing Point Bonita, is approximately 1/4 mile off a steep, rocky lea shore and should only be used with fair weather and seas.  It is often said, “If the fishing boats are not there, you should not be either.”  I have personally seen waves breaking across Bonita Channel when conditions in the Main Ship Channel were relatively comfortable.

If you are headed West or South (or if headed north in less than optimal conditions) use the Main Ship Channel.  As mentioned earlier, forecast sea conditions for that day can be found online at

The South Channel  (aka; the one that isn’t there!)

Several years ago, a popular cruising book author indicated there was an unmarked channel to the south running about .7 miles off shore, which could be used in fair weather.  Unfortunately, the South Channel does not exist and its use continues nearly every year to claim vessels and lives.  The mythical South Channel lies off a lea shore where the bottom slopes continuously from deep water to the shoreline.  Just the conditions needed to create a surf break.  A few years ago, a friend of mine who is a much better sailor than I am nearly lost his boat in this area.  He was arriving from the South, a few miles offshore, when conditions (wind and waves) began pushing him to leaward while crossing the bar.  Near the end of his bar crossing, he was convinced he would be driven ashore.  Only his experience and skill saved him.  The moral of the story … stick to he Main Ship Channel.

Point 2 on safety out the gate:  Use the Main Ship Channel in all but the most benign of conditions where Bonita Channel is an option, and under no circumstances use the mythical South Channel.

Conditions Outside the Bar

Conditions encountered outside the bar determine safety and comfort during a sail outside the gate.

Track forecasts for several days or a week prior to your planned trip.  Look at weather forecasts, check for wind expectations, and track swell models.  Several links will be provided below to help.  Unfortunately, links change over time.  My hope is this links will still be live when you read this, however, I can’t guarantee it.  However, I am sure there will be others to replace them, which with a little effort on your part can be found.

First a couple of definitions:

Combined Seas (generally referred to as Seas)
The combination of wind waves and swell, without considering each component part separately.  For example, today’s forecast is for:  NW winds 15 to 25 kt with gusts up to 30 kt this morning. Wind waves 3 to 5 ft. W swell around 3 ft at 12 seconds. patchy fog this morning.  This particular forecast doesn’t mention the 1 foot secondary swell coming from SW at 16 seconds.  I know it is there, so I will be adding it in.

Take the 5 ft from the 3 to 5 ft wind waves, add to it the 3 ft primary swell at 12 seconds, and the 1 ft secondary swell for a forecast combined seas of 9 feet at 12 seconds.

Significant Wave Height 
The average wave height (trough to crest) of the highest third of the waves.  Using a different internet source in the example below, you can see that today’s forecast is for SWH of 6 ft at 12 seconds, increasing later today to 7 ft at 11 seconds.

Every sailor’s skill and experience level is different, as are the levels of each member of your crew.  These are two things that should always be primary in making the decision to proceed outside the gate.  In my case, I use the follow criteria:

  1. Combined Seas greater than 12 feet; or
  2. Period less than 9 seconds; or
  3. Significant Wave Height equal to or greater than Primary Swell ( E.G. 9 ft at 9 seconds or less, or 11 ft at 11 seconds or less); or
  4. Wind (including gusts) greater than 33 knots; equals a decision not to go (No Go).

Looking at today’s forecast … Seas 9 feet, Period 9 seconds, Significant Wave Height 6 at 12 seconds, wind NW 15-25 gust to 30 … everything looks OK.  The gusts to 30 might be of some concern, however, it is within my personal guideline.
Note:  Tradewinds uses the same guidelines when deciding to approve a member request for a sail outside the gate.

Forecasts are great, however, to be safe, I would get current conditions by checking a report from the San Francisco Buoy

5-day plot - Wind Direction Wind Direction (WDIR): NW ( 320 deg true )
5-day plot - Wind Speed Wind Speed (WSPD): 13.6 kts
5-day plot - Wind Gust Wind Gust (GST): 17.5 kts
5-day plot - Significant Wave Height Significant Wave Height (WVHT): 5.6 ft
5-day plot - Swell Height Swell Height (SwH): 4.6 ft
5-day plot - Swell Period Swell Period (SwP): 7.7 sec

and a swell model

With the exception of the period, everything at the buoy seems better than forecast, and I know from past experience that the period provided in the buoy report isn’t just the primary swell I look at, it is more of a total of primary and secondary swells.  It quite often is less than 9 seconds without bothering me.  As long at it is greater than the wave height I am good.

Point 3 on safety out the gate:  Seas 12 feet or less, Period 9 seconds or greater, SWH less than period length, winds less than 34 knots.

A final thought before I provide you with a list of reference links.   During the planning stages of the Advanced Coastal Cruising class, the class is asked to track weather and sea state for several days before departure.  No later than 3pm on the day before we leave the dock each person is to submit a Go/No Go recommendation for the following morning.  It isn’t unusual that the conditions result in a No Go recommendation.  The requirements are pretty straight forward, so the vast majority of class members make the correct recommendation … then, about half of them follow the No Go recommendation with a “but, I am willing to do it because I know there is an instructor on board.”

My question is this … knowing that Tradewinds has established these criteria as an outside limit for safety, why would I (you can put your name here also) be willing to risk my life, the lives of my crew, and that of my vessel just to provide an experience that is outside safety guidelines.  If you are a student in any sailing class, one of the things your instructor will be looking at while deciding to certify you is if you posses the mental consciousness required to be a Captain.  Do you?  Because, the role of Captain, is a very serious role that you take on.


Here is a list of the links used above.


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Coast Piloting Part I – Dead Reckoning

I’m not a fan of the term Coastal Navigation.  It has become quite popular over the past several years, however, it’s a bit too vague to properly describe the process of safely operating a vessel in coastal waters.  The proper term, used for at least two centuries, is Coast Piloting.  Piloting is navigation which involves determining the position of a vessel relative to geographical/terrestrial reference points.  With coast piloting, the reference points can be visually seen and then identified or matched to a reference on a chart of the area. To be able to identify that point on a chart requires you to have a pretty good idea of where you are to start with.

As an example, a chart of Drakes Bay in Northern California looks very much like San Quintin Bay in Mexico, over 600 miles to the southeast.  Not having a general idea of where you are will result in some major errors in navigation.  15 miles south of Drakes Bay, 5 miles offshore, is safe water nearing the approach to The Golden Gate.  15 miles south of San Quintin, 5 miles offshore, is the Sacramento Reef, one of the most dangerous reefs on the pacific coast.  Not a good mistake to make.  The answer to having a good idea of where you are is Dead Reckoning (aka DR, Deduced Reckoning, or Ded Reckoning,) which is the primary topic of this tip.

Dead Reckoning is determining the position of a vessel by applying the ship’s course and speed to the last known accurate position (fix.) An ongoing plot of course, speed, time, and distance is marked on a chart, resulting in an approximate vessel position. A DR position is an approximate position, not allowing for the effects of tide, current, wind, helms person error or compass error.  Whenever possible, the DR position must be updated to a more accurate fix, using bearings to visible objects and other lines of position that might be available.

A DR plot requires a known starting point, and is referred to as “taking departure.”  This would be your last known accurate position fix, and is marked on the chart with a ⊗ as well as the time (noted horizontally on the chart).  The size of the circle represents the degree of accuracy of the fix.  This, and subsequent “expansion circles” around later DR positions indicate all possible positions of the vessel, and will be discussed further below.

Items to be included in the plot are:

  • Time of each DR and/or fix position using 4 digit military time with no punctuation (e.g. 0800 or 1500)
  • Time is written horizontally for fixes, and diagonally for DR positions
  • Course line (carried out for two extimated future DR positions)
  • Above the course line, the letter C followed by the 3 digit course in degrees true for the ordered course (e.g. C 165).  The letter T is not needed.  Although many professional navigators will disagree, it is not recommended that courses are designated in degrees magnetic.
  • Vessel speed in knots (e.g. S 5)

Update the DR plot at least:

  • Once an hour, on the hour
  • At every course (or speed) change
  • Any time a line of position is established

At every fix (including running fixes) the DR plot should be reset and a new DR plot  begun.

In this example taken from day two of the Tradewinds Advanced Coastal Cruising class,  departure was taken at the Pillar Point safe water buoy [RW “PP” Mo (A)] at 0900, on a course of 300 degrees true to pass just to the SW of Southeast Farallon Island.  Speed was set at 5 knots.  Visibility due to haze/thin fog was estimated to be approximately 1 mile, therefore, no identifiable features would be available to take a bearing until arrival at Southeast Farallon.

As a precautionary measure, the navigator assumed a possible steering error of 5 degrees, and created an expansion circle around each DR position.  Knowing that a traffic separation zone would be reached approximately 7.5 miles into the planned course, and would require nearly an hour to cross, the watch was notified to pay special attention to possible commercial traffic from 1030 to 1130.

Estimated time of arrival off Southeast Farallon was 1400.  At 1345, Southeast Farallon Light was sighted through the haze, and a bearing of 338 degrees magnetic was taken.  Variation was applied, and a bearing of 352 was laid out on the chart, providing a single line of position.  A depth of 180 feet was noted, providing a second line of position, and a fix obtained.  Based on the fix, the average speed over ground was 5.2 knots, and the steering error was only 2 degrees.  The DR was reset to the new fix, and the remainder of the trip to Drakes Bay plotted.  C 316 for 24 minutes, followed by a turn to C 012. Estimated time of arrival at the entrance to Drakes Bay 1745.


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