How to chart a course across Lake Ontario

[shaant01]

Hello,

I am a new sailor and want to understand how to chart a course. I understand that it is rather complex so I want to leave it simple for now. This is more hypothetical as I am not experienced enough to sail that far. I don't own any nautical charts so I have been using an app called OpenSeaMap. Let's assume that I want to sail from Port Credit to Niagra-on-the-lake (which I have included below). It is a distance of 27.66 nautical miles and it says I would need to sail on a true course of 127.46 degrees. However, I want to use a magnetic compass. The magnetic deviation is -10.1W. I understand that if the deviation is west, it is added to the true course, so I would sail on a course of 137.47 degrees on the compass.

Can someone tell me if that is even remotely correct? I have not accounted for other factors such as the tide.

Thank you!

 

[Foswick]

You've got the right idea. I will say that, if you intend to sail by magnetic compass, you can round to the nearest degree. Fractions of degrees are pretty meaningless since you can't sail that accurately anyway.

So, your heading would be 137 degrees magnetic. But, that is only a small part of the picture.

You can ignore tidal currents. Where I live, these can readily exceed 5 kts (or considerably more). But, where you live, you can ignore them. Wind-driven currents and seiches are not negligible. Folks with experience on the Great Lakes can better advise you on the best way to predict and compensate for those. (I have no experience on the Great Lakes.)

But, winds have a complicated effect on the heading you ultimately need. When winds produce a current, that is easy enough to compensate for. You just need to know how long you will be in that current. With that information, you know how far in the direction of the current the boat will be translated down-current. From that, you can determine what heading you need to sail.

Put differently, let's say that you want to sail directly east-to-west and there is a current travelling directly south at 1 kt. You calculate that it should take you 5 hours to reach your destination. If you sail directly west, you would then arrive 5 nm south of your intended destination because the current will have translated you 5 nm south. Right now, the water that will be at your destination is 5 nm north of your destination. You need to sail toward that water because, 5 hours from now, that water will be right at your destination.

The problem is that now your heading is different, your trip is longer, and your speed is different than it would have been if you had been able to sail directly toward your destination. There are ways to mathematically account for all of that, but none of them are worth the effort because your speed is not that predictable and currents will change over time and distance.

Additionally, even ignoring currents, your boat has a certain amount of leeway. This is the tendency of your boat to side-slip away from the wind a bit. This varies considerably with the kind of boat, the wind speed, the wind angle, wave action, etc. It is best not to try to predict it with any precision. Just know that it exists and is not negligible.

All this to say that, yes, your destination is 137 magnetic, but if you sail that heading, even if you could sail it accurately, you will almost certainly miss your destination. At that destination, being off just 2 degrees will make you miss the mark by a mile. And, if you can sail a 17-foot sailboat with a magnetic compass within 2 degrees of your desired heading for a trip that will likely take something like 8 hours, then you are superhuman. You would do quite well to sail within 5 degrees, which would put you within 2.5 miles of your destination.

The good news is that none of this matters much. To make that trip in your boat, you need to be out when conditions are clear and winds are moderate. So, you should be able to spot landmarks the whole time. A useful skill to develop would be to take advantage of this fact to hone your triangulation skills. You should be able to shoot an azimuth to the CN Tower and another to Burlington Canal Bridge. Maybe Old Fort Niagara? With those two readings, you can pretty well pinpoint your location. You use periodic checks to adjust your heading.

So, you initially head out at 137 degrees. After an hour, you see that you are a mile north of where you expected to be. So, you adjust your heading a bit south and check again in an hour. If you have been sailing accurately at 137 degrees, that also tells you the combined effects of leeway and currents that you experienced that hour, which might inform how you sail for the next hour.

My first "real" sailing trip was from Seattle to the Canadian border. It was the first time I had ever sailed on saltwater, much less navigated. It was a 22-foot boat. I was a fairly competent sailor and did have experience as an airplane pilot. So, I very carefully plotted out each leg with exact headings and estimated times, based on hourly forecasts. Once I got through the locks and hit salt water, I never looked at the plan even once. I had underestimated how easy it was to simply see where I was going, or see well enough to get me closer. And, I overestimated how accurately I could sail a heading, in particular because winds/traffic/conditions often forced me to sail on a different heading than my destination.

 

[dlochner]

There are no tides on Lake Ontario. There is a general west to east current, however on most days it is negligible.

Learning to chart a course and read charts is best done in a structured manner. A good course or book will explain deviation and variation as well as other navigation issues, such as set and drift, while walking you through the process.

The Canadian Power and Sail Squadron would be a good place to start. They can also help you get your Canadian license.

CPS | Canadian Power and Sail Squadrons is a non-profit organization and the foremost educational boating authority in Canada

www.cps-ecp.ca

 

[Joe]

Forget the magnetic, analog compass. It's nice to have for watching your apparent wind angles or keeping track of lifts and knocks. But no one, not ever Josh Slocum, can hold an inexpensive magnetic compas to less that 5 deg. error. It's not the current, it's the chop (and the skipper's attention span) that will make things difficult in a small boat. No, use what every other boater and sailor does. it's called a GPS. You can use a chart plotting app for your phone that gives you all the info you need, which is true wind direction and speed, boat speed and boat direction (or it's course).
Enter in your waypoint on the gps and it will figure your "velocity made good" which is your speed of progress to the waypoint. Especially useful when sailing upwind and you must zig zag... not sail a direct course line.

You can find a simple hand held gps, which is what I used for many, many years for under $100, if you want a map it'll be another 50-100. (I think the small handheld chartplotter screen is nearly useless btw) but... if you have a paper chart, you'll be able to plot your progress. Lots of fun doing that. Also helps if you should get caught in the fog, which will scare the ba jesus out of you the first time....(don't forget you are required to carry a sound generating signal device, just for that situation.)

If you're become serious about navigating with a compass, see if you can acquire a copy of John Rousmanierre's "The Annapolis book of Sailing". Look for an older copy, a used bookstore perhaps, and you'll save significant money. Anyway, this is a book that should be the foundation of your sailing library... He devotes serious time in the book to navigating, piloting and celestial. Piloting is what you'll be most interested in. You will need your compass, a chart, a pencil with eraser, a ruler, a time piece and a speed indicator to tell you how fast you're boat's travelling. Good luck

 

[jssailem]

Hello @shaant01 and welcome to SBO Forums.

Simple is fine. It is called dead reckoning. Canada expects their sailors to have proper charts. Either paper or electronic, I believe is now acceptable. If you want to understand the skills I like to use a current paper chart with the navigator’s toolset. You can get a free printable paper chart here at the NOAA chart office. Chart 14800

Our progress with hand held computers takes skills of navigation and displays the results. The question is are the results what you expected to get.

Your calculation of magnetic compass heading is correct.

As was said by @Foswick the use of a heading needs less precision and for you sailing will still be accurate. Your compass on the boat will provide you with integers 137 degrees, not fractions of a degree in decimals.

I suggest you do the work up over short distances along the coast. Then get on the water and test your sail plan. You will quickly gain the knowledge of dead reckoning, the influence of changing winds and currents as they impact your planning.

Chart a course from the docks at Mississauga to the light off Gibraltar Point. While you are aided by the shoreline and the sights of Toronto, you can focus on maintaining a compass course on the boat.

Good luck.

Ps. I use the fancy electronic tools but I still carry the coastal charts and navigation tools on board. It helps me know that what the computer says is what I wanted to know. A way of saying I asked the computer the correct question.

I have never forgotten the programer mantra. “Garbage in garbage out”.

 

[shemandr]

I second the suggestion of some "Power" Squadron training. Among other benefits you will develop an awareness of how to be underway. That is, to collect observations of the world around you and how to use that information to determine where you are, where you are heading, when you can expect to arrive and how to avoid hazards along the way. It is practical hands on training. No matter what means you use to collect information - compass, GPS, Radar, Depth Finder, Relative Bearings, Navigational Aids, Eyeballs, Hearing etc. - your enjoyment on the water will be enhanced by being in the moment.

 

[kloudie1]

This is a great general reference for sailing :
Chapman Piloting & Seamanship 69th Edition (Chapman Piloting and Seamanship): Chapman, Eaton, Jonathan: 9781950785490: Amazon.com: Books
It can be found for less money . It's great to learn the language and as the title says, navigation..

 

[kappykaplan]

I have never forgotten the programer mantra. “Garbage in garbage out”.

 

[David in Sandusky]

I, too would recommend a GPS, and/or app like Navionics on your smartphone. But I made my first, 40+ mile crossing of Lake Erie using dead reckoning on our compass. Here are my thoughts:

- In the west end of Lake Ontario, you can assume no currents.
- You may lose sight of any shore on your crossing - no sweat, dead reckoning on your compass does work.
- There is a 3% to 10% error rate using dead reckoning over 30 miles, so
- Find out what tall landmarks can guide you into Niagara on the Lake.
- Consider joining the Great Lakes Cruising Club (GLCC) or buying a port guide for Lake Ontario. They will give you a good description of what it looks like, and what landmarks can guide you into port. Here is such a description from the GLCC web site for Niagara on the Lake:

"The Niagara Bar, with depths of 8 feet, lies 1.5 miles northwest of the entrance to the Niagara River. The outer end of the Niagara Bar is marked by Niagara Bar light buoy 2, situated 3.25 miles north of the river entrance.

"A bank with least depths of 5 feet extends 0.8 miles off the east side of the entrance and is marked by a flashing green light buoy 3, located near the entrance range line. A prominent water tower at Niagara-on-the-Lake is located 0.8 miles south-southwest of the Fort Mississauga Light, light list number 548.

"Brock's Monument, located 6 miles south of Niagara-on-the-Lake, is also prominent."

Fair winds and following seas for your crossing. Go for it!

 

[Foswick]

I think they have probably already heard of GPS and understand the benefits. The question was about navigating with a compass and is absolutely a valid question, in particular for a new sailor.

I actually get a little concerned when I hear sailors eschew things like compass navigation, dead reckoning, and even pilot pilotage in favor of GPS. It is even increasingly rare for people to carry paper charts. There is a list of reasons that is a negative trend, and not only because I am an anachronistic curmudgeon. (I am, but that is not the only reason.)

I don't want to hijack the thread with a debate about the role GPS "should" play in sailing. But, let's not steer a new sailor away from learning basic compass navigation.

 

[shaant01]

Yy

You've got the right idea. I will say that, if you intend to sail by magnetic compass, you can round to the nearest degree. Fractions of degrees are pretty meaningless since you can't sail that accurately anyway.

So, your heading would be 137 degrees magnetic. But, that is only a small part of the picture.

You can ignore tidal currents. Where I live, these can readily exceed 5 kts (or considerably more). But, where you live, you can ignore them. Wind-driven currents and seiches are not negligible. Folks with experience on the Great Lakes can better advise you on the best way to predict and compensate for those. (I have no experience on the Great Lakes.)

But, winds have a complicated effect on the heading you ultimately need. When winds produce a current, that is easy enough to compensate for. You just need to know how long you will be in that current. With that information, you know how far in the direction of the current the boat will be translated down-current. From that, you can determine what heading you need to sail.

Put differently, let's say that you want to sail directly east-to-west and there is a current travelling directly south at 1 kt. You calculate that it should take you 5 hours to reach your destination. If you sail directly west, you would then arrive 5 nm south of your intended destination because the current will have translated you 5 nm south. Right now, the water that will be at your destination is 5 nm north of your destination. You need to sail toward that water because, 5 hours from now, that water will be right at your destination.

The problem is that now your heading is different, your trip is longer, and your speed is different than it would have been if you had been able to sail directly toward your destination. There are ways to mathematically account for all of that, but none of them are worth the effort because your speed is not that predictable and currents will change over time and distance.

Additionally, even ignoring currents, your boat has a certain amount of leeway. This is the tendency of your boat to side-slip away from the wind a bit. This varies considerably with the kind of boat, the wind speed, the wind angle, wave action, etc. It is best not to try to predict it with any precision. Just know that it exists and is not negligible.

All this to say that, yes, your destination is 137 magnetic, but if you sail that heading, even if you could sail it accurately, you will almost certainly miss your destination. At that destination, being off just 2 degrees will make you miss the mark by a mile. And, if you can sail a 17-foot sailboat with a magnetic compass within 2 degrees of your desired heading for a trip that will likely take something like 8 hours, then you are superhuman. You would do quite well to sail within 5 degrees, which would put you within 2.5 miles of your destination.

The good news is that none of this matters much. To make that trip in your boat, you need to be out when conditions are clear and winds are moderate. So, you should be able to spot landmarks the whole time. A useful skill to develop would be to take advantage of this fact to hone your triangulation skills. You should be able to shoot an azimuth to the CN Tower and another to Burlington Canal Bridge. Maybe Old Fort Niagara? With those two readings, you can pretty well pinpoint your location. You use periodic checks to adjust your heading.

So, you initially head out at 137 degrees. After an hour, you see that you are a mile north of where you expected to be. So, you adjust your heading a bit south and check again in an hour. If you have been sailing accurately at 137 degrees, that also tells you the combined effects of leeway and currents that you experienced that hour, which might inform how you sail for the next hour.

My first "real" sailing trip was from Seattle to the Canadian border. It was the first time I had ever sailed on saltwater, much less navigated. It was a 22-foot boat. I was a fairly competent sailor and did have experience as an airplane pilot. So, I very carefully plotted out each leg with exact headings and estimated times, based on hourly forecasts. Once I got through the locks and hit salt water, I never looked at the plan even once. I had underestimated how easy it was to simply see where I was going, or see well enough to get me closer. And, I overestimated how accurately I could sail a heading, in particular because winds/traffic/conditions often forced me to sail on a different heading than my destination.

Thanks for the information! I would like to know how to chart an accurate course in case the electronic tracker breaks down. As you say, it’s not hard to use familiar landmarks to reach the destination. I have Navionics until I set up an actual system. I am not sure how to triangulate my location with azimuths yet but there’s time to learn. Cheers!

 

[shaant01]

There are no tides on Lake Ontario. There is a general west to east current, however on most days it is negligible.

Learning to chart a course and read charts is best done in a structured manner. A good course or book will explain deviation and variation as well as other navigation issues, such as set and drift, while walking you through the process.

The Canadian Power and Sail Squadron would be a good place to start. They can also help you get your Canadian license.

CPS | Canadian Power and Sail Squadrons is a non-profit organization and the foremost educational boating authority in Canada

www.cps-ecp.ca

I will check out that resource and look into some online courses. Thanks!

 

[Foswick]

I am not sure how to triangulate my location with azimuths yet but there’s time to learn.

That's easy with a paper chart, a course plotter, a pencil, and a handheld compass, though it takes a little practice to do well.

You use a handheld compass to shoot an azimuth to a landmark you can positively identify on the chart. (An azimuth is a measurement of the bearing of a distant point. Let's say you shoot an azimuth to a landmark and find it at a bearing of 92° T (92 degrees true). You draw a line on the chart that runs 92° T through that landmark. Then, you shoot an azimuth to another landmark and find it at a bearing of 187° T. You draw another line on the chart that runs 187° T through that landmark. Where the lines intersect - that is your position.

The farther apart and more distant the landmarks, the more accurate your position estimate will be. You can also shoot a third azimuth using the same procedure. When you do this, the three lines will likely not perfectly intersect at one point. Instead, they will form a small triangle where they almost intersect. This is because your measurements are not completely precise, nor are the lines you plot on the chart. It is normal to assume your position is in the direct center of that triangle. If the triangle is too large to adequately identify your position, then you need to repeat the process because your measurements or plotting were off.

When I say that you shoot an azimuth, then plot, that isn't exactly the best way. Best to get both bearings, then plot them both. This is because you want a measurement of those bearings as close together in time as possible because you are still moving. The more time that passes between readings, the less accurate your position estimate will be.

Keep in mind, it is tricky to get an accurate bearing with a handheld compass on a boat in the water. If I am being immodest, I am very good at it, and still can only reliably get to within a few degrees, most of the time. (Even on land, being +/- 1 or 2 degrees is normal.) On the water, I will attempt an azimuth a few times and average them, on the hope that my errors will average out.

There is a whole can of worms here, if you want to be as accurate as possible. If you are using a built-in compass in your boat, and navigating by that compass, it will not always agree with your handheld compass. They can disagree up to several degrees. Ironically, the little handheld compass is likely more accurate, though your reading of it might not be.

(The reason for this is that the built-in compass is more subject to the influence of structures on the boat itself. People that really care have their compass "swung" or do it themselves. This is a sort of calibration process that results in a table that describes how far off the compass is for any given heading, and in which direction. Honestly, most sailors can completely ignore this. You simply cannot sail to a compass heading with enough accuracy that the compass error really makes much difference, unless the error is high on most headings. It is really only valuable if you need to sail for days on a known magnetic heading.)

 

[jssailem]

You can use a Boy Scout compass as a tool. ( Fair Accuracy)
You can stand behind a binnacle compass, sight over it at your target, use the reciprocal draw a line to your location.
(Fair Accuracy)
Or you can use binoculars with a compass inside to get it only a bearing but also estimate the distance from the landmark.
(Good accuracy)

 

[Tally Ho]

You can use a Boy Scout compass as a tool. ( Fair Accuracy)
You can stand behind a binnacle compass, sight over it at your target, use the reciprocal draw a line to your location.
(Fair Accuracy)
Or you can use binoculars with a compass inside to get it only a bearing but also estimate the distance from the landmark.
(Good accuracy)
View attachment 227164

I have a pair of those.

But for a 20+ nm sail, I would note my compass heading and head out. You can almost see the target shore…and if not, just sail to your compass heading until you can.

If sailing at night, make sure you some reference point that you can spot in the dark (lighthouse, towers with lights, etc).

There is a HUGE lighted billboard sign that I can see for 10 miles or more just outside of my marina…makes ”finding” my way back home in the dark pretty easy

Greg

 

[shaant01]

Hello @shaant01 and welcome to SBO Forums.

Simple is fine. It is called dead reckoning. Canada expects their sailors to have proper charts. Either paper or electronic, I believe is now acceptable. If you want to understand the skills I like to use a current paper chart with the navigator’s toolset. You can get a free printable paper chart here at the NOAA chart office. Chart 14800

Our progress with hand held computers takes skills of navigation and displays the results. The question is are the results what you expected to get.

Your calculation of magnetic compass heading is correct.
View attachment 227149
As was said by @Foswick the use of a heading needs less precision and for you sailing will still be accurate. Your compass on the boat will provide you with integers 137 degrees, not fractions of a degree in decimals.

I suggest you do the work up over short distances along the coast. Then get on the water and test your sail plan. You will quickly gain the knowledge of dead reckoning, the influence of changing winds and currents as they impact your planning.

Chart a course from the docks at Mississauga to the light off Gibraltar Point. While you are aided by the shoreline and the sights of Toronto, you can focus on maintaining a compass course on the boat.
View attachment 227150
Good luck.

Ps. I use the fancy electronic tools but I still carry the coastal charts and navigation tools on board. It helps me know that what the computer says is what I wanted to know. A way of saying I asked the computer the correct question.

I have never forgotten the programer mantra. “Garbage in garbage out”.

Thanks for the resources! I will check them out soon. I noticed the first course you charted came out somewhat different than mine. Is it from Port Credit to Niagra-on-the-lake? Cheers!

 

[jssailem]

note my compass heading and head out

That is precisely what I did a few years ago when I left Victoria, heading to Port Angeles to return to the USA from Canada. It is 15º 32' + East magnetic deviation. It was clear (Visibility 10+ nm) when we left Victoria. A Sea Fog formed in the middle of the Strait. Visibility went down to 2nm. We continued our course heading, following the compass. As we approached Port Angeles, the fog cleared. We drifted maybe 1nm west due to tidal currents. It was a glorious day.
Here is the chart.

 

[Tally Ho]

That is precisely what I did a few years ago when I left Victoria, heading to Port Angeles to return to the USA from Canada. It is 15º 32' + East magnetic deviation. It was clear (Visibility 10+ nm) when we left Victoria. A Sea Fog formed in the middle of the Strait. Visibility went down to 2nm. We continued our course heading, following the compass. As we approached Port Angeles, the fog cleared. We drifted maybe 1nm west due to tidal currents. It was a glorious day.
Here is the chart.



View attachment 227165

And to be fair, I have GPS and a chart plotter on my boat…

But we did learn dead reckoning in my sailing class. Probably have a divided ruler in the nav desk…but honestly haven’t pulled them out in 10 years


Greg

 

[Captain Larry-DH]

You’ve received some good advice and feedback above. I think taking the Power Squadrons course will serve you well and answer your questions.
As a new sailor on a Siren 17, you may be better served to focus on developing sailing techniques, weather assessment/judgment, and seamanship skills - and eschew the old-fashioned methods of paper charts and magnetic compass. You don’t have the nav-table space to properly manage and use paper charts while you sail (especially if conditions are sporty) and your small boat moves with quick motions making it an unstable platform to try to get accurate compass/bearing readings. I recommend you master and use a chart plotting app (e.g. Navionics or Aqua Maps) as opposed to manually plotting courses. The Power Squadrons course will teach you how to do the manual calculations that underly the apps, and that will help you as well. However, paper charts are going away (whether the luddites like it or not) and it makes good sense to use better technology so you can focus on other important things.

 

[jssailem]

honestly haven’t pulled them out in 10 years

It is funny about the timing. I was sorting the Navigation table just this week, pushing the Navigation tools aside to get at a part I was seeking. I never thought to just toss them out. They are a safety tool when electrical systems go on the fritz.