Monday, June 13, 2016

Can exceptional behavior be considered ordinary?

The answer is Yes, according to Justice Wilmer in the 1955 case of Velox vs Viking Monarch, wherein one anchored vessel dragged anchor and collided with another when both were sheltering from a severe storm, when there were maneuvers and procedures that might have avoided it if taken.

The nicely put conclusion was:

"I have been reminded, and quite properly reminded, that no seaman can be called upon to exercise more than ordinary care (see Rule 2a below); but I think it is necessary to observe that when a seaman is called upon to face wholly exceptional conditions, ordinary care of itself necessarily demands that exceptional precautions may have to be taken."
In other words, it is the ordinary practice of seaman to take exceptional precautions in exceptional conditions, just as it is to take normal precautions in normal conditions.


RULE 2 Responsibility

(a) Nothing in these Rules shall exonerate any vessel, or the owner, master or crew thereof, from the consequences of any neglect to comply with these Rules or of the neglect of any precaution which may be required by the ordinary practice of seamen, or by the special circumstances of the case.

(b) In construing and complying with these Rules due regard shall be had to all dangers of navigation and collision and to any special circumstances, including the limitations of the vessels involved, which may make a departure from these Rules necessary to avoid immediate danger.

See also our very convenient (free) presentation of the Nav Rules and all related  documents we call Pocket Nav Rules Handbook.

Friday, June 3, 2016

Inside Passage and R2AK Weather

Here is a peek at an old page we had for our onboard training trips to Petersburg. We ran across it today by accident and realized this could be valuable to those doing the R2AK at the end of the month, or anyone headed north this summer.  So we checked and updated the links and added a couple new ones. You can see the page more clearly at the link below. This view is just to show what is there.  To view the links here you have to right click and choose back to return.

Saturday, May 28, 2016

Chart Plotting Tutorials

We are updating several plotting videos we use in our online courses, which were pretty good twenty years ago, but pretty clunky by modern standards. We start out here with a compilation of text descriptions to short videos.  For the time being, these are just YouTube videos of the old Flash movies. We will redo them from scratch in the near future.

Measure Distances
1. Short distances with the miles scale
2. Short distances with the latitude scale
3. Long distances in steps

Measure Directions
4. Magnetic direction using parallel rulers
5. True direction using Weems plotter
6. True direction using a string plotter

Plotting positions and courses
7. Using Lat - Lon scale
8. Plotting COG from a plotted position
9. Using the Starpath card plotter method

1. To measure a short distance using the miles scale...
(1) Set divider tips to span the distance.
(2) Move the dividers to the miles scale with one tip on 0 miles to get the approximate distance.
(3) Then slide the other tip to the nearest integer on the scale, and read the fractional part from the tip that was on 0.

General Notes
Miles scales will appear on most charts with scales of 1:80,000 or larger. When no miles scale is given, use the Latitude scale for the miles measure. Each minute of Latitude equals 1 nautical mile.
When using electronic charts, the display software will typically include an option on the menu bar for measuring ranges and bearings. With these functions, you just drag the mouse cursor from one point to the next and the distance between points and the bearing between them show numerically on the screen.

Video Notes
We will measure the distance between the two points marked by these fingers. The dividers used are a speed bow, which we adjust with the knob between the two points. We are measuring the distance from a channel marker buoy to a daymark at the entrance to a channel.

Once the dividers are accurately set to these points, we move the dividers — with out changing their separation — up to the miles scale, which in this case was at the top of the chart. It could be anywhere on the chart.

Notice that we first put left tip on the 0 and look to the right tip to see that we have here a distance of just over 2 and one half miles (nautical miles). Next slide the dividers to the left until the right tip is exactly on the 2, and read the fractional part from where the left tip hits the tenths scale. Count out the number of tick marks from the 0 back to the left to see that the fractional part is about 0.64. The total distance is then 2.64 nautical miles.

Whether or not the 0.04 part has any significance at all depends on how carefully we have done the other parts. Normally, such a measurement would only be done to 0.1 mile precision, so this answer would be stated as 2.6 miles. Top

2. To measure a short distance using the Latitude scale...
(1) Set divider tips to span the distance
(2) Move the dividers to the latitude scale on the left or right side of the chart, roughly due east or west of the segment you are measuring.
(3) Set one divider tip on some latitude of a whole number of minutes, such at 00' or 05' or 40'
(4) Let the other divider tip fall onto the latitude scale wherever it might. The second tip can be at a higher or lower latitude that the first since we care only about the distance between them.
(5) Figure the distance using the rule that each minute of latitude equals one nautical mile. Always double check the latitude scale to be sure you understand what the tick mark or graduation marks mean. Sometimes the latitude scale is marked in tenths of minutes, other times in various units of arc seconds, such as a mark every 5".

General Notes
The latitude scale can be used for a miles scale on all charts, even if they happen to have a specific miles scale printed on them. Remember to go more or less straight left or right to reach the latitude scale — and that this must be measured from the latitude scale (sides of the chart), not the longitude scale (bottom and top of the chart).

That is, do not set dividers to some distance near the top of the chart and then put them on the latitude scale near the bottom of the chart. On a small scale chart which covers a large area, if you make a shift like that you can introduce significant errors in the distance measurement.

A note on the reason for this: Nautical charts are made in what is called the Mercator projection. This type of projection is very convenient for navigation since North is always the same direction on a chart — usually toward the top of the page — and all bodies of land and water have the proper shape. This latter point is important since it lets us determine what the compass bearing is from one point to another from the chart.

This seemingly obvious task is not so simple as it might seem. Near the North Pole for example, or at any very high latitude, this type of chart (Mercator) is not possible and consequently it is difficult to determine bearings or directions from a chart in these areas. Remember if you are standing at the North Pole, every direction is South! — a good hint that we have a charting problem in this region.
In any event, away from the polar regions, Mercator charts serve us well for navigation, but there is a price to pay for the bearing convenience. Although the shapes of lands are right, their relative sizes are not. Greenland is not larger than the US as it appears on a Mercator projection, it is in fact less than one quarter the size of the US. So it is with all land masses on Mercator charts. They are bigger at higher latitudes. Put another way, the number of inches per degree of latitude or per nautical mile is higher at higher latitudes.

It is always true that 1 minute of latitude = 1 nautical mile, but the physical size of this unit will vary with latitude. That is why when using small scale charts (those that cover a large area) we must use the nearest latitude scale to measure distances.

Video Notes
This is the same measurement explained in the previous example (Short line with miles scale), but this time we use the latitude scale to read the miles. If you have not done so, please read through the previous example first.

After setting the separation, we move the dividers straight left (or right) to the nearest latitude scale along the side of the chart. Here we set the top tip to the latitude of 37° 20' N and let the bottom one fall where it will. We chose this one simply because it was the nearest whole value due west of our measurement. This particular latitude scale is marked with broad bands every 1' of latitude. Although the numbers are not shown, the bottom tip is at latitude 37° 17.4' N.

What we care about here, though, is only the separation, which we can count down from the 20' mark to see that it is 2.6' = 2.6 nautical miles.

In this very common operation of reading a latitude, or in this case a latitude interval, it is very important that we first check to see what the tick marks mean along the scale. Don't guess this, always double check it. Different charts use different conventions on what is bold and how many minutes or seconds there are per tick.

We usually check this carefully once, and then actually write it on the chart. That is, had we used this chart before, there would be a "19' " label and an "18' " label hand drawn in along the border. On this chart, the next printed label is located out of sight here at 37° 15'. Top

3. To measure longer distances by walking the dividers...
(1) Set divider tips to a convenient whole unit such as 1.0 or 2.0 miles
(2) Start at the first point and "walk" the dividers along the route, counting the total number of steps.
(3) At the end, squeeze the divider tips together to measure the last, smaller step.
(4) Take dividers back to the lat scale or to a miles scale to measure the size of the last step and add this to the total number of steps for the full distance.

General Notes
This is the standard method for measuring longer distances. In most cases, you must balance out the best choice for the step size. If it is too large, you will lose accuracy going around corners, but if it is too small it takes longer to measure.

On electronic charts, this measurement is typically done by setting up a route of multiple waypoints between the two end points. Then the route properties can be displayed which among other data will include the total distance from start to end. Such a route could be temporary or saved. The properties will include the bearing or course between waypoints as well as the time of transit based on some input speed.

This procedure can also be used to measure or estimate the time a trip will take. If traveling at 7 knots, set dividers to a spacing of 7.0 miles, then walk off the route. Each step is 1 hour of travel time.

Video Notes
This example shows measuring the distance between two buoys some distance apart. It starts down and around a peninsula, up a channel, and into a bay. Dividers are first set to a separation of 2.0 miles using the latitude scale and then walked along the path.

There are 5 whole steps along the route, and then the dividers are squeezed together to span the last step. When moved to the latitude scale, we see it is about 1.1 miles. The total distance is then 5 x 2.0 + 1.1 = 11.1 miles (that is, nautical miles). Top

4. To measure the direction of a line on the chart...
(1) Align parallel rulers with the line in question.
(2) Move the parallel rulers without slipping to the nearest compass rose and align one edge with the center of the rose.
(3) Read true orientation of the line from the outer ring of the compass rose, or read the magnetic orientation from the middle ring of directions. 
General notes
Take care to read the rose in the direction of interest, not its reciprocal. These are all obvious matters, of course, but when tired or in a hurry, it is easy to overlook the basics unless we train ourselves to check and double check even the simplest matters in all applications. (Remember, as a navigator, you always run the risk of having the helmsmen do exactly what you tell them to do!)

"Compass rose" is an unusual term for this diagram on a chart, but it is used universally, even on high latitude charts that do not include any compass directions at all on the diagram. On typical compass roses, however, you have 3 scales, an outer scale showing true directions relative to true North at 000 and a middle scale which is rotated by the local magnetic variation so it reads magnetic headings, and then a third inner ring that shows compass directions marked off in compass points (each point is 11.25°).

If you want to be double sure that you did not move or slide on the way to the compass rose, you can walk the dividers back to the line after reading or marking the direction on the rose. If the parallels do not line up when you return, you will have to repeat the whole process, since you do not know if you moved coming or going.

Video Notes
The hand traces out the line in the direction we wish to measure. The first step shown is just a trick to use dividers to help align the parallel rulers.

Place a tip on the line and then slide the parallels up against the tip. Then rotate the parallel rulers back down to align their edge with the line on the chart. This method is a good way to get a careful alignment even when bouncing around in a seaway.

Then use one hand to hold down the aligned ruler, and use the other hand to move the other part of the rulers away from it. This is taking the first step with the rulers. Then change your pressure to hold down the one you moved, and bring the back one up to it.

When the ruler edge will finally reach the center of the compass rose, align it with the center of the rose and read the appropriate ring where the parallel ruler edge crosses it. If the light is poor or when bouncing around, it may be necessary to draw a line along the ruler edge crossing the scale and then read the scale.

To read the scales, we must do just as when reading the latitude scale or any other scale. Count the tick marks in between the labeled ones to be sure we know what they stand for. A common mistake can be to count them as 1° each when they are actually 2° each, or vice versa.

In this example, there is 1° per tick mark on the True scale and the direction we want is 320° T. Notice that it is difficult to read along the edge of the clear plastic rulers. Drawing a line will help in a case like this. Top

5. Measuring directions with a rolling plotter...
(1) Align parallel plotter with the line of interest
(2) Roll plotter to nearest meridian and place center of plotter's scale on that meridian.
(3) Read line direction from the plotters scale, where the meridian crosses it.

General notes
This example is the same as last example, but with a Weems plotter, rather than parallel rulers. Read in that section about the trick of using dividers to get the alignment, or in this case, a first step toward the alignment, since we can fine tune that one using this tool (see Video Notes, below).

Meridians are the lines of longitudes, vertical lines on most charts. This measurement can also be made on a parallel of latitude (horizontal lines on the chart) using the diagrams on the two edges of the plotter. These plotters work very well when you have good chart table area. It is sometimes difficult to get to use them near the edge of a chart, so we always have parallel rulers at hand if needed.

These plotters are very convenient, but you must use true bearings — as opposed to using parallel rulers and the compass rose, in which case you can choose which scale, true or magnetic, you prefer. When using these tools, you must have the local magnetic variation in mind at all times and make the corrections whenever you are relating to compass courses or bearings.

Video Notes
As in last example, the finger traces out the direction we wish to measure. And, as explained in the last example, we use the dividers to align the plotter with the charted line.
In this case, though, we fine tune that alignment using the thin black line printed on the plotter itself. You could use the edge of the plotter or this line, but we have found that using this line is more accurate. To do this, look through the plotter and micro-adjust the plotter orientation until the line on it coincides exactly with the line on the chart.

Then carefully roll the plotter to the nearest meridian line and align the center of the plotter's compass rose scale with the meridian as shown.

Read the heading from where the meridian crosses the scale. Note that the diagram reminds you with small arrows that if looking NW use the inner scale and when looking SE use the outer scale (see last frame of video). The bearing we want in this example is 320 T, in the NW quadrant. The reciprocal is 140 T, which is in the SE quadrant.

As cautioned in the last example, we must be even more careful here to get the right direction. Generally keeping some rough numerical estimate in mind will solve this problem. Top

6. Measuring true course with a string plotter...
This is a method found useful for many paddlers and other small craft operators that have little room for tools or surfaces to use them on.

Drill a hole (if needed) in the center of a 0-360° protractor and insert a string about 18 inches long. Tie knots at both ends and use as illustrated.

For some applications, the center of the protractor can be placed on your position or other reference mark, but in other examples, as the one shown here, the center is offset so the string can pass through both points of interest.

The edge or some other vertical or horizontal lines on the protractor must be aligned with some straight lines on the chart, but it is rearley a problem to make this orientation. The bearings or directions are read from the protractor where the string crosses the scale. These directions will always be true directions which must be converted to magnetic if used with a compass, which is the usual case.

Video Notes
There is no video here, just slides.
Slide 1 shows general use of the tool, aligning the protractor with some vertical or horizontal reference and stretching out the string to read a direction.

Slide 2 shows the alignment and the string in more detail. In this example, the plotter is used to measure the course from a plotted position to the pass between two islands.

Sldie 3 shows the string crossing the protractor scale and going through the plotted position. The true direction of this course is 307 T. If the local magnetic variation were 20° East, then the magnet course would be 307 - 20 = 287 M.

The compass conversion rule is "correcting add east," where "correcting" means going from Magnetic to True. We are going the other way, so we subtract. If there is ever any doubt about this, just go to a compass rose and draw a line from center to either true or magnetic course and read the "converted course" from the other scale on the rose. In short, a compass rose is just a graphic table of compass conversions, from True to Magnetic or vice versa.

This type of string plotter could be called "Sutherland plotter," named after kayaker Chuck Sutherland who, to our knowledge, is the inventor of this idea for a measuring device. Top

7. To plot a position using Lat / Lon scales...
(1) Double check the Lat value from original source.
(2) Identify this Lat on the Lat scale on the side of the chart, double checking the tick mark spacing before hand.
(3) Use plotter or dividers to transfer this latitude to chart and draw a short line in your approximate position.
(4) Repeat the process using the Lon scale at the top or bottom of the chart. Draw another short line to intersect the Lat line, and the intersection is your position.
(5) If this is a position fix, draw a small circle around the intersection and label this position with the time.

General Notes
There are numerous ways to carefully plot a Lat / Lon position. The key issue is doing it precisely. In these days of GPS, much of our position navigation has been reduced to simply plotting a position on the chart. Needless to say, we don't want to do a bad job of all we have left!

But, jokes aside, this is a crucial part of navigation regardless of how we got the info in the first place. And it is one of those things that seems so easy, we might not treat it seriously enough. Which is a mistake. It cannot be done too carefully in most cases.

If the plotter won't reach the region of your position as shown in the video — which it certainly won't in many cases — then we have a bit more work to do. First, on the latitude scale itself, set the dividers to the distance from the given latitude to the nearest parallel shown on the chart, and then mark that distance on the chart near the approximate longitude. Then use plotter to draw the short Lat line at that position, rolling the plotter down from that nearest parallel. Then do the same for the longitude.

Video Notes
In this example, the first step shown is the double checking of the latitude tick mark spacing, by counting off the steps between the two labeled latitudes. Here the bold bands mark off 1' intervals from 36° 50' on up. One divider tip is then placed at the 52.7' mark and the plotter is rotated till it is parallel to a latitude line. In this case, this was performed by aligning the vertical line in the center of the plotter with a meridian on the chart.

Once the plotter is parallel, it is slid up to the divider tip to mark the proper latitude, and a short line drawn in the region of the position. We know where this should be from looking at the longitude scale and the longitude we must plot.

Then the process is repeated for the longitude.
The conventional plotting symbol for a position fix is a full circle about the intersection. Other positions on a chart are marked with other symbols, such as a half circle for Dead Reckoning positions, and a square or triangle for estimated or projected positions. Top

8. To plot a course line from a position...
(1) Orient a plotter or parallel rulers with the desired direction using the compass rose.
(2) Move the plotter back to the position and draw the course line.

General Notes
This process is essentially the reverse of the exercises shown in the Directions section. There we had a given line and used the compass rose to measure its orientation. Here we start with a given orientation, and wish to draw a line through a specific point in that direction.

Generally the line is our intended course away from a known position. The course could be specified in True or Magnetic terms, but in either case it is just one unique line on the chart. The only difference is which ring we use on the compass rose.

As with plotting positions, this is one of the key operations in chart plotting. We have a known position which we might have obtained from electronic equipment or from some piloting technique, and we have a known course we wish to sail which will take us to our destination. Or, we could be under sail, and we are simply plotting out our course over ground (COG) as given from the GPS.
Generally it is the COG that we need to plot here since this is the way we are actually moving. The compass heading of the boat is the way the boat is pointed but is not necessarily the way the boat is moving.

Video Notes
In this example, we have a Course Over Ground of 238M, which we wish to plot away from our 1352 position, which is already plotted.

We use the dividers to help align the plotter. First use the divider tip to carefully count off the numbers on the magnetic ring on the compass rose. Again, we wish to confirm what the tick marks stand for since the bearings are only labeled every 30°. Once we find 230, we count out the next 8 degrees and then plant the point at 238M.

Next slide the plotter up to that point and then rotate it till the center is aligned along the edge. Then carefully roll it back down to the 1352 position and draw the line. Top

9. Position plotting with card plotter...
First you have to make a plotter as described at the end of these notes. Next you must prepare your charts with a few extra meridians and parallels over the region you will be traveling, also described at the end.

There is obviously some time involved in this preparation to use this method, but once completed it lasts for a long time and will speed up your accurate position plotting by a great deal on the charts that apply. For tricky passages or for racing navigation where quick navigation is essential, this simple method has proven extremely valuable many times now since the advent of digital read outs, back in the old LORAN days. With it, and very little practice, you can plot an accurate position on a chart about as fast as you can read them from the electronics.

Video Notes

In this example, we plot: 48° 23.25' N, 122° 33.82' W on a chart with scale of 1:25,000. This method requires a separate card, or at least corner of a card, for each chart scale it will be used with (explained below).

Step 1. Align the right side of the card with the nearest meridian of whole minutes of longitude of your position, in this case 122° 33'. (This meridian has to be on the chart. If it did not come that way, then this is one that we had to add ourselves, as was done in this case, in red.)

Step 2. Slide the top edge of the card up to the nearest parallel of whole minutes of latitude of your position, in this case 48° 23'. Then slide it farther up to match the decimal part of your latitude, in this case 0.25'.

Step 3. Count left, to the west, from the meridian along the top edge of the card to mark the decimal part of your longitude, in this case 0.82' and mark your position with a point. Then it is a good idea to immediately label this position with the time it was valid.

How to make a "Starpath card plotter"
We call this a Starpath plotter so that this particular method is easy to refer to. There are numerous plastic plotting aids on the market, but we have not seen any like this, and we have not seen any that work as well. Furthermore, it is a valuable exercise to construct the device and plot the extra chart lines as it gets the user a bit more involved with the actual scales being used. This technique was developed for racing navigation back in the days when we first had electronic positions, but no electronic chart plotting—to be used when we had to plot fast in dangerous conditions, as in rounding a corner closely at night or transiting a narrow channel in strong current.

Use any piece of cardboard. Index cards work well — we have many times cut the back out of a notepad to make the cards. Next study the chart you will be using for this to see what the decimal scales are for latitude and longitude. Generally this method works well for the common scales of 1:40,000 and 1: 80,000 charts or 1:25,000. For larger scales it works even better, and for smaller scales there is not much need for this type of plotting.

Note from slide 2 that you mark the latitude scale going down the right side and the longitude scale going across the top to the left. The scale should be marked in decimal degrees, which in turn means it is most convenient when the GPS output is in decimal degrees — as opposed to degrees, minutes, and seconds, which is awkward to plot.

A separate card or corner is needed for each chart scale used. Also the latitude and longitude scales must be divided into tenths, which is not given on all charts. The nautical miles scale will do it for the latitude, but you will have to interpolate the longitude on some charts, with 6" = 0.1' etc.
Since most charts do not have parallels and meridians drawn every 1', we usually need to add extra lines to use with this plotter. Once added, it is helpful to label them in the vicinity of your travels. Needless to say, we should double check these labels with the chart scales themselves.

Once prepared, this is a fast, convenient, and accurate way to plot. Time spent in preparation and practice should prove rewarding. Again, though, this is intended for fast plotting in somewhat special circcumstances. For most routine navigation, simple use of parallels and dividers, covered elsewhere in this plotting tutorial, should do the job just fine.

PS. If you are in the Navy or on any large government vessel, then this might be something to keep in mind, as they still have to plot positions frequently on a paper chart. Maybe that will change with new ECDIS rulings in 2018, but there remains sound logic for the paper plotting. Top

Wednesday, May 18, 2016

An Overview of Ocean Weather

An Overview of Ocean Weather
from Selected Links to  Articles and Videos

(1)  Mariner’s Weather Checklist Before Departure absolute must do list!

(2) Weather Maps—Where To Get Them and What We Get? ...the next item below shows what the maps look like.

(3) Atlantic and Pacific Weather Briefings  ...Most efficient way to get maps underway or at home

(4) Weather by Satellite Phone  ... covers non-commercial options.

(5) Reading and writing on weather maps index to a series of videos focusing on confirming GRIB forecasts with NWS maps.

(6) Grib Viewers — New Developments and Special Features
 * * * Onto tactics and real weather data * * *

(7)   ... vast resource for local weather

(8)  ... similar resource for Pacific weather

(9) Storm track awareness   ...a video illustrated series of articles on sides of a tropical storm

(10) High Seas Forecasts and Tropical Cyclone Alerts by Email Request    ... the importance of text reports in the tropics and how to get them

(11) Marine Weather Services Chart — How to Make Your Own longer printed by NOAA but still a fundamentally important resource.

Reference books:

Thursday, May 5, 2016

Is the Moon Waning or Waxing?

Periodically I read through one of our online course discussion forums, which has been accumulating over the past 15 years—sort of like skimming through a dictionary— and very often I run across extended notes buried on a special topic there that have long been forgotten, but deserving of some fresh air. This is an example, namely the question came up in cel nav course about deciding if the moon is waning or waxing.

So that of course first got the standard cel nav treatment, but following that were the parts that were a bit more interesting.  

Here is a copy of that forum post from 2004:

We are back from our Alaska training cruise (will write about it later), and on watch till we leave for the Pacific Cup Yacht Race on June 28. Then again off watch for 2 weeks.

Moon phases, appearances, and terminology issues are always puzzlers. There are definitely some things that change with location, but most are the same.

It is likely more an issue of which way are you looking to see the moon, rather than which hemisphere you are in at the time. At 2° N with a moon dec of 25° N, for example, i am looking north to the moon at mer pass, rather than the more common view south to mer pass from the NH.

Things that are the same:

(1) the words "waning" and "waxing" have their same English word meanings always, everywhere. Waning getting smaller, waxing getting bigger.

(2) the moon is waxing when it is moving away from the sun and waning when moving toward it. This is the key point and also one that is not so easy to picture... without a picture.

(3) the moon is full when it is precisely on the opposite side of the earth from the sun (GHA sun - GHA moon = ±180°), and there is no moon or a "new moon" when the sun and moon are on the same side (GHAs are equal).

(4) the moon moves eastward through the stars at about 12° per day (360°/30 days). This is true always, everywhere. If you see the moon next to Aldebaran bearing 190 M at 10 pm, for example on one day, then the next day at 10 pm you will see Aldebaran at roughly 191 M (sun moves 360°/365 days) and the moon will be 191-12 = 179 M. 

From Emergency Navigation

[These bearings are approximations since it is really the great circle arcs across the sky that are about 1° and 12°, not strictly their bearings on the horizon, but if their peak heights at mer pass are less than about 45°, this is a usable approximation—a point covered in some detail in the Emergency Navigation book.]

(5) the side of the moon that is lit up is the side nearest the sun. If you draw a line connecting the "two horns" of the moon — or equivalent points for other phases — and then draw a line perpendicular to that, you have a line pointing toward the location of the sun.

From Emergency Navigation

The above (5) statements are always true from any location, any time. And from these we should be able to answer all questions about moon phases.

Things that are different:

(1) When looking south to a body's daily motion, we see it's east-to-west motion as being from our left to our right, whereas looking north to view the east-to-west motion we see it moving from our right to our left.

(2) The shape of a crescent moon changes from "C" to "D," or vice versa, when looking to the north versus the south to see the moon. This is consistent with all of the above, but when it comes to making up rules on what the moon is doing (waxing- or waning-wise) based on what we see, such as the note below on whether or not the moon is "telling the truth,"  then we must qualify these with which way we are looking to see the moon, which in turn is often over simplified to specifying what hemisphere we are in.

"The Moon is always lying" the Northern Hemisphere

There is a French saying that "The moon is a liar" (La lune est menteuse), which can be used to determine if the moon is waxing or waning. I have known of this for some years but never knew what it meant, nor how to apply it. Recently a student mentioned in passing that it must mean that the shape of the moon is a letter and the letter tells us what it is doing, but it tells us wrong! 

Well, indeed, it is as simple as that. "Croître" means "to wax" and "Décroître" means "to wane," as shown in the figure. When the moon shows us a "C" (croître, waxing) it is lying, it is not waxing but waning, and vice versa when it shows us a "D" it is not décroître but croître.
Don't believe me; I am lying.

—Thanks to Capt. Jean Faubert for filling in the details on this saying, and confirming that many French-speaking navigators have indeed learned it this way.

Celtic Goddess Symbol

When I explained this discovery to my teenage daughter [actually not a teenager any longer as I re-post this today], who I thought might be interested since she studies French, she said, "Fine, but isn't it simpler to just recall the Celtic Goddess symbol?," which she immediately sketched and explained: the waxing moon on the left represents maiden; the full moon in the middle, mother; and the waning moon on the right, crone. The symbol is unforgettable, and I had to agree with her. Thanks Britt. 

Wednesday, April 13, 2016

Connecting a Mintaka Duo Barometer to Expedition

There is much virtue in having an accurate barometer integrated into our echart programs. This can be accomplished with just an accurate sensor without displays of its own, or we can interface a full function device like the Mintaka Duo as well. Atmospheric pressure and its trend remains our key indicators of wind and weather changes, so having this displayed prominently at all times as we navigate or carry out route selection is always helpful. We typically rely on numerical forecasts that start with our present or recent positions, so seeing the true pressure we measured with an accurate barometer compared to the predicted pressures is a fundamental check on the forecasts… rather like comparing the depth sounder to the chart and tide tables as we enter shallow waters. 

Programs like Expedition add to the interpretation of what we see because they offer versatile graphic displays. The Mintaka Duo has its own app for versatile display and analysis but the convenience of comparing graphic plots of pressure with wind speed and direction is another bonus that program offers.

Connecting the Duo to a computer takes place in two steps, first prepare the Duo to output a NMEA sentence the program can read, and then configuring the program to read that input. This is essentially the same process for any barometer capable of this interfacing. These two steps are outlined below, illustrated by a video to show the steps in process.

Set up the Duo to export the NMEA sentences

Note that this only has to be done once.  Once the sentences are being output, it will continue to do so till you tell it to stop. It does not matter if it is removed from power; it will continue to out put the sentences when powered back up.

1. Download and install the Mintaka Commander App  from the “Connect your Duo to a Computer” link at  There is a PC and a Mac version. Follow instructions there to insure that you have the USB drivers installed (also available at that link).  PC computers may  need to update their Java utility as well. Again, links are provided.  If needed the drives and Java update should just take a couple minutes.

Note there is no installer for either version.  You are downloading the actual app or exe, which you can put where you like and then just execute  it by clicking it. You may want to make a short cut, or move the app to your desktop.

2. Plug the Duo's USB cable into computer and launch Mintaka Commander App

3. On a PC, select the COM port that has been assigned to the USB port you are plugged into.  On a Mac you will see the serial number of your device.  (After you have run the app once, the data from the unit will be stored on your computer so you can return and look at the data off line if desired.  (If the COM port is uncertain, then open Device Manager and unplug and replug the device to see which port number shows up in the list of Ports. You might also see there the one being used for GPS and maybe one for Sat Phone, or maybe others.)

4. Wait for the databases to sync with the computer.  This takes a minute or two the first time it is connected; later connections this will be quick. Each pressure has a unique UTC stored with it along with other data, which are organized according to time intervals steps. There are up to 10 files like this to be synced.

5. Once synced and the graph is fully plotted, you have a couple ways to proceed. From the menu bar you can select Commands/ Run a command and type h and enter to get a list of commands, and there you learn that the one we want is AS which stands for Auto Sample. The actual command takes the form AS 5 XDR, which means send out the XDR sentence every 5 seconds.  If you just do AS 5 you will get out both XDR and MDA. ECS programs will want one or the other.  The NWS VOS ships using Turbowin will use AS 5 TURBOWIN   You can use any time interval in seconds that you choose.

6. So one option is just enter the command that way and it will start sending out the signals, but you will not know it.

7. The other option is to actually connect via the Terminal mode: main menu / Terminal / Connect.  Then in the status window below (where the cursor will be blinking) type AS 5 XDR and enter.  And then you will actually see what is being put out from the USB port. 

This will look something like


where you will get one line every 5 seconds.

8. Then disconnect the Terminal:  menu / Terminal / Disconnect, and you are done.

9. Close Mintaka Commander.  Note this must be closed before we can connect to the ECS because only one device can be connected at a time.

The Mintaka Commander App offers many valuable interactions with the Duo, which are explained in the Starpath help file and online at

If you should want to stop the auto sampling, connect to the app and run the command ASQ.

 Video illustrating the steps listed above.

Configure Expedition to display pressure in a Number Box and Stripchart.

1. Launch Expedition

2. On the top LEFT of the menubar, Click "Expedition" drop-down

3. Select:  Instruments / Serial and Network Ports

4. The COM port used in the Mintaka app should show up on the left. Select that one. (If it does not, be sure the Mintaka app is closed. Then try again.)

5. Set these Connection Settings: NMEA 0183 Instruments; 57600 Baud rate; 8 bits; None Parity; 1 Stop bits; Boat 0 Boat (0 def)
(Note the default baud rate of the Mintaka is 57600, but if there should be any reason for it, you can change this with a command in the Mintaka app.)

6. Leave unchecked: Redirect incoming data and Command.  Leave checked: Use position fix; Validate checksums

7. Then click Apply and then click RAW DATA button and wait up to 5 seconds for data stream to show (The send frequency of 5 seconds was set above in the Mintaka app.)  After data confirmation, close all set-up windows.

8. On the top LEFT of the menubar, Click "Expedition" drop-down, once again.

9. Select: Settings / Channels and set  Barometer “Damping (seconds)” to 0 on the left, and Barometer “Display precision” = 2 on the right.

Now we need to set up a Number Box to display the  barometric pressure "Baro" as follows:

10. On the top RIGHT of the menubar, Click "Window" drop-down and check or confirm "Number boxes" is checked. You can use any of the three boxes to show the baro data. You can display more than just Baro in one of the boxes.  

11. Click anywhere in the Number box window to display the "Edit" number boxes button, add Barometer, and configure the box to taste (i.e., Bold and with yellow background). Click the small + next to Barometer in the left panel to open the display options.  That baro display will then be persistent till you change it. It should be reading the same pressure you see on the Mintaka Duo, except Expedition will now be showing two decimals, whereas the Duo itself shows only one on the front display.

12. Launch Stripchart by clicking "Expedition" drop-down (top LEFT of the menubar), then “Applications" / "Stripchart"

13. At this point you can either add the baro to a chart layout already in use or if this is the first one you will see Bsp (boat speed) as  the default.

14. To add baro to an existing chart, click "View" / "Number of channels" and increment the number by one to add a new data strip.  It will be added as "Bsp" by default at the bottom of screen.

15, Right-click "Bsp" and click "Edit this stripchart" to access Settings and choose "Baro".  Click OK and the pressure feed will begin tracing across the stripchart.

16. Do menu Save to save the new baro strip chart template (This step saves the template, but not related to saving the data).  The video below shows a few ways to use the chart for reading pressure and tendency, including:
— use of tool tip
— note middle pressure shown is not a scale element, it is actual pressure at the moment.
— use of grid option
— use of wands and computed sd for storm warning in the tropics.
— recalling past chart data from the log file.

Video illustration of the points above.

A special thanks to Andrew Haliburton for itemizing the steps of this process, which was the starting point for the lists above.

Monday, March 14, 2016

Right of Way in the Traffic Lanes

In a recent article on how to know if you are in the lanes or not, we received a question (below) in the comments that has come up before. We answered there, but expand a bit here with actual links.

"Rule 10 (j). A vessel of less than 20 meters in length or a sailing vessel shall not impede the safe passage of a power-driven vessel following a traffic lane."

Does this rule apply to ANY "power-driven vessel following a traffic lane", or just to power-driven vessels >20 meters which are using the shipping lane?

Asked another way, if two boats each < 20 meters are in the shipping lanes, one is following the edge of the lane motoring north, and another crossing over the lane heading west (on the stb. side of the boat heading north), which rule applies? (Rule 10j or "boat to stb"?)

Finally, same boat <20 meters, motoring north following the traffic lane, but with a boat also < 20 meters under sail crossing the lane (heading east, and to the port side of the boat motoring). Which rule applies? (Rule 10j or sail over motor?)

There seems to be a lot of confusion about this situation in the Sound.
There are two key references that answer your questions. First is the full set of Nav Rules, and we have a super convenient document online called Starpath Pocket Nav Rules Handbook.  You can use it for quick reference with all related documents in one place—in fact, they are all on one webpage. You can also save it to your phone.

The next key document is the Puget Sound VTS Users Manual, which very specifically addresses points raised in the questions. This is a very useful document for all Pacific Northwest boaters.

In Rule 10 (j) the statement “following a traffic lane” means a vessel in full participation in the VTS, which in practice are ships and tow boats, and other larger commercial vessels.  The key part of their full participation is their scheduled radio contact with the VTS center, along with actually following the lanes. These vessels are to be contrasted with vessels that just happen to be in the lanes at the moment, but later or earlier along their voyage they take other routes that do not follow the lanes.

The vessels you refer to are not "following the lanes," they just happen to be in them at the moment.

The User's Manual explains who is required to have full participation and who may participate and under what conditions they may do so when not required.

20m is not required;  >40m is.  In practice, recreational vessels are expected to participate passively, as defined in the manual. (I leave these terms undefined here to encourage reference to the Manual itself.)

The fact that the track of a vessel is parallel to the lane,  inside or outside of the actual lane boundaries, is not the key factor when interacting with a vessel clearly not required to follow the lanes with full participation.

First part answer:
“Does this rule apply to ANY "power-driven vessel following a traffic lane", or just to power-driven vessels >20 meters which are using the shipping lane? “

So the answer to that is NO,  and again using the lane is not the issue; it is participating in the VTS that matters,  which is here called following a lane.

Second part answer:

“Asked another way, if two boats each < 20 meters are in the shipping lanes, one is following the edge of the lane motoring north, and another crossing over the lane heading west (on the stb. side of the boat heading north), which rule applies? Rule 10(j) or 'boat to stb' ?”

Assuming neither are “following the lanes” as described, these are just two vessels interacting in open water that has lanes defined in them, in which case normal crossing rules or sail-power rules apply.

On the other hand, if there are indeed ships following the lanes in the near vicinity, then both of these vessels must not impede them.  Non-participating vessels are encouraged to use the inshore zones, not the lanes themselves, which would minimize such three vessel encounters.

Third part answer:
“Finally, same boat <20 meters, motoring north following the traffic lane, but with a boat also < 20 meters under sail crossing the lane (heading east, and to the port side of the boat motoring). Which rule applies? (Rule 10j or sail over motor?)”

Again, we have the same answer.  I can see there could be confusion about the wording, but I believe that once these points here are noted this should remove that confusion.

In other words, if you are not in full participation with the VTS, which in almost all cases, you would not be doing unless you are a vessel required to do so, you gain no special rights when sailing in the lanes, regardless of your course.  When you see other vessels not following the lanes in this sense, you interact as you would in open water, assuming there are no ships near by, as they then become, in the wording of  the Racing Rules (whether or not you are actually racing), obstacles to your course.

We are standing by for discussion if it might come up.

Saturday, March 12, 2016

How to Buy, Register, and Download Canadian Echarts

This note was originally about ENC type echarts alone, but it turned out that the process of buying, registering and downloading the echarts is the same for both ENC (vector) and RNC (raster) echarts, so I have changed the title of the note, but not the body of the text, which still reflects the original motivation for the article, which was ENC.

When it comes to the actual installation, however, these two chart types from Canada are quite different, because of an extra layer of encryption applied to the RNC.

Also looking ahead a bit, we see below that the process is a bit long, and has to be done in the right order, but once this part has been done and you have a username and password with CHS, subsequent registrations and downloads are very easy.  The RNC install, however, is another issue and we will have to come back to that later. The ENC install is very simple.

* * *

In an earlier note on the Naming and Boundaries of ENC eCharts, I discussed the unique situation of needing one specific Canadian ENC if we wished to use all ENC in the Eastern Strait of Juan de Fuca, as might be the case, for example, when using Expedition for the Swiftsure or Victoria to Maui Yacht Race. This note is a follow up on that one.

In process of working with individual copy protected Canadian ENC, we learn quickly how lucky we are in the US with free echarts and super convenient access. It is all doable, but frankly tedious, and indeed there is no help online nor available from their telephone tech support. The phone support can help with BSB raster charts, but not the ENC, though I suspect now that the process is in fact identical for Canadian ENC and RNC.

This process is outlined in detail below, because the right path is not obvious, and any wrong turn spins out into a dead end.

(1) Choose the chart you want from the very useful CHS Interactive (graphic) Index (save the link, it is not so easy to find.)  The single chart at hand at the moment is CA470075, which they label with its paper chart name: V-3440 - Race Rocks to/à D'Arcy Island.

(2) Buy the chart. In principle there are numerous dealers of individual Canadian echarts, but the only one I found that could actually sell this is our friends at Captains Nautical Supply. In principle, this could all be done over the phone.

After you buy it you will get an email back from Captains with this information. The original prices are quoted at CHS in Canadian dollars as $25, which I assume this is as well.
Figure 1. Proof of purchase

Figure 2. Link to where you register and download.

(3) Register the chart, which takes place in several steps: we set up two accounts, download the chart, and install the chart.

Here are the steps, with apologies again for what seems maybe over explained, but one wrong step and it breaks. We start with the link provided by CHS when we purchased the chart  (, which actually takes you to a different link:   We are getting early hints here that we have to stay sharp, ie there are two sets of instructions originally mailed to us that both go to the same link, which is not actually the link they go to.

We end up here:
(My original snag was I thought the blue fields were just table headers, but they are indeed the links.)
Figure 3
This takes us to Figure 4, and we then go direct to the bottom link. It is not clear what the top part is referring to. I think GC means Government of Canada.

Figure 4.

If you have already in the past registered, you can log in here, but if not we now start the process of setting up an account with the Sign Up link on the next page.

(If you later need to download a second copy, this is where you would log in to do that, and it would be straight forward. But you must then log in with the same account that you registered the chart with originally.)

Figure 5

Figure 6
Figure 7

NOTE  they have strict rules on names, hints, questions and answers. I have marked these in red boxes.

Figure 8

Figure 9
IMPORTANT NOTE. Be sure to save this information so you can regain your login if needed.

Figure 10

IMPORTANT NOTE: If you delay very long at any page you will get the following message when you hit Next or Continue. I am not sure how long you have, but it is not long. Maybe just 5 min or so.  If you get this at the end of the process, as I did once trying to record all of my answers etc, it is very discouraging. You get to start all over.

Figure 11

With no errors, the Figure 10 Continue button will take you to Figure 12 below.

Looking at that one, you will not have received a DFO passcode as so far we did not give any email address.  So in this window you will choose Self Registration. 

Figure 12

After choosing Self Registration, you get the screen below and now we can start the real registration.

Figure 13

Figure 14

Figure 15

NOTE in the form below (Figure 16) you must enter a Unit Type, even though it is not marked as required.

Figure 16

Figure 17

The next figure is a summary of your registration information with CHS. Print this or save it as a pdf, as you may need it to recover the chart or a login.  Maybe a call to them would get it, but not sure.

Figure 18

Then when you save this, you will be back to your products page, which will not have any,  and you can add them.

If you do not get sent back to the next page below, then just start over and on the first page (Figure 5 above) enter your Username and password selected earlier, and you will get here.  This is where you paste in the code for that chart that was mailed to you.

Figure 19
NOTE in the above we do not use the link License a Product.

After you add this product, the same page will then have it listed further down the page  under the section Active Products.

 And it is here where we download the chart.

IMPORTANT NOTE. It might take several clicks.  Click it once and wait a few seconds.  If nothing happens, try again. In one test I had to try 3 times, and this behavior has been confirmed to me by other users.  But be sure to give it 5 or 10 seconds between clicks.

Figure 21.

And then we get our chart, which you just save to your downloads folder.  This zipped file is then all standard ENC format.  It is easy sailing from here on. Again, if you need another copy for another computer, you can start from the beginning and just log in.

Figure 21

Below is a video on how to install this ENC into Coastal Explorer, along with related notes on using this program to select, download, and install US ENC.

Sunday, March 6, 2016

Naming and Boundary Conventions on ENC eCharts

In a recent article (The Strange World of Electronic Chart Boundaries)  I pointed out the unusual nature of the shapes and names of electronic navigation charts (ENC), which are the digitized vector versions of the raster navigation charts (RNC). The latter are echarts made from exact graphic copies of the paper charts, and in that sense their sizes, boundaries, names, and scales are immediately understandable to anyone familiar with the paper charts.  This is not at all the case when we move to the vector ENC charts.

There were several questions raised in that note that have taken more research. In short, that note just described the situation without providing any reasons for it. Since then I have made progress on understanding these ENC properties, thanks primarily to good support from NOAA's Office of Coast Survey (OCS), who do indeed care about the best use and understanding of their products.

There are two basic factors that lead to the unusual properties we end up with on the presentation of the ENC—I am not discussing the content of the charts at all here, just the issues of size, shape, boundaries, and scales.

First, the US ENC are made from the available RNC. That is, to make a vector chart of a region, step one is bring out the largest scale RNCs of the region, and then digitize these products in a standard ENC format. Digitizing means converting a curved shoreline or depth contour into a sequence of straight line segments and storing a data base of these points, which is then included in the ENC files we load. Then an echart program can draw the chart on the fly each time we change a display scale or move to a neighboring or overlapping ENC. It is a complex process to make these, but much of the data are already digitized and all new survey data comes in digitized as well.

Then at the location of each aid to navigation (ATON) the data describing it are entered into another data set included in each ENC. (Though probably not so well known, the header file components of RNC kap files include the precise Lat-Lon of each prominent aid as a georeference point of the RNC, which insures these are in the precisely right place to match the Light List and latest Local Notice to Mariners; recall RNC and ENC are updated as needed every week or so.) It is this step of the ENC production that could add much more ATON information than possible on an RNC, and often this is the case—but not always. In the case of rock symbols, for example, the ENC descriptions sometimes include less information that we can get from the rich set of RNC rock symbols described in Chart No. 1.

That is the way the ENC are produced, but they cannot be published in this direct one-to-one relationship between a new ENC and the long established RNC, which brings us to the second factor affecting the ENC boundaries we see.

The reason they cannot be the same is the International Hydrographic Office (IHO) has standards on these ENC echarts that all participating nations must follow, and the US is indeed a participating member [see References].  This situation has pros and cons. The main con is, the US does not have complete freedom to produce ENC in any scheme they might deem most logical based on our RNC system. The main pro is we end up with charts that match an international standard that better serves the thousands of foreign vessels that visit the US each year, and indeed then makes foreign ENC familiar to US mariners visiting their waters.

The primary IHO restriction that affects the boundaries and scales of US ENC is no ENC can overlap an adjacent one within the same scale band. That brings us to a key factor in understanding the boundaries of ENC, namely the concept of scale band or usage band.   The IHO defines 6 usage bands, and recommends the scale ranges that each of these bands should cover. The table below summarizes these as best I can tell.  These definitions are useful for selecting charts in catalogs and for understanding the names, and in turn the ENC boundaries we see  in navigation programs.

The US values do not coincide with the IHO values because the US had been making these ENC before the IHO made their recommendations. The British Admiralty ENC is  marked with a footnote [*] because although they do use the IHO values for their own ENC, they do not use the name Scale Band, but more often prefer Usage Band.  I think the reason for that is they have a vast worldwide chart distribution network (they distribute the charts made by other nations), and different nations have different definitions of the actual scales in each usage band as shown. The Canadian one is notably different.

The scale band is a key to understanding the names of all ENC. In the case of US products, the first digit after “US” is the scale band. Thus for the chart we discussed earlier, US5WA18M, the US means US product, and the 5 means this chart has a scale band 5 (i.e. between 1:5,000 and 1:50,000). The WA means the chart is either wholly within the state of WA or when covering overlapping states, the majority of the chart is in the state of WA.

Scale bands 3 to 6 are generally associated with a specific state. Bands 1 and 2 are often labeled:  EC (for East Coast), GC (for Gulf Coast), and WC (for West Coast), but there are some overlaps in these descriptors with the state descriptors.

We can think of the “M” as a reminder that the native units of these charts are metric (although we can display them in other units if we choose), or we can think of it as a filler since all ENC worldwide must be 8 characters long—
I would have to agree that dealing with an extra M is better than dealing with leading zeros.  

The fact that the actual sequence of numbers (i.e. the 18) do not always follow a logical sequence along a waterway is just a matter of history in the production sequence, much as the chart numbers of the RNC are not in any particularly logical order.  If anything, the ENC are more often in sequence than the RNC counterparts.

Thus we have this sequence of charts coming in from the ocean toward San Francisco:

US1WC01M (1:3,500,000)
US2WC12M  (1: 1,200,000)
US2WC06M (1: 811,980)
US2WC05M (1:868,003)
US3CA14M (1:207,840)
US5CA12M (1:40,000)
US5CA13M (1:20,000)

The first two (scale bands 1 and 2) can overlap as they are different scale bands, but none of the three band-2 charts can overlap.  Likewise the last two here (band 5) cannot overlap and will change charts at a specific line.  The NOAA Online Interactive Catalog is the best way to study this, short of having the built in convenient presentation of Rose Point navigation software, mentioned earlier.

Note too that the US ENC chart numbers are only unique within state designations and scale bands. Thus in our US5WA18M example, we can have a US4WA18M as well as a US5OR18M, but there are never two charts with the identical name.

In learning to use this system we might also keep in mind that the US ENC scale bands are not the same as historically been used in the US for paper charts. The US Chart Scale Classifications are defined in Chapter 1 of any US Coast Pilot and Bowditch as:

The IHO paper chart categories are also shown, in part to show these are broad categories with no definitive boundaries. In my own experience, I tend to think of 1:40,000 to 1:80,000 as "medium," being between "large" (less than 40k) and "small" (more than 80k).

It is not clear if this difference in scale range definitions between our traditional paper charts and modern ENC has any significance.  It certainly provides navigation schools and USCG exams nice ways to make trick questions, but probably not much more than that.  The standard US paper chart classifications never had, to my mind, much influence on practical navigation, but the new ENC scale band system does indeed have a meaning, i.e. it determines the third character in the name of any ENC, worldwide.  It could be that the upcoming new edition of Bowditch will address this matter.

So now we can go back to our example from the earlier article to see why the boundaries of the ENC equivalent to RNC 18474 (ie
US5WA18M) are what they are—again, the NOAA Online Interactive Catalog is the best way to follow along.  When NOAA sets out to cover the ENC charting of the region covered by 18474 (scale 1:40,000), they start out by digitizing the largest scale RNC charts that cover that region. In this case, the north half of this chart is covered by RNC 18449 at a scale 1:25,000. (The south half of 18474 does not have any larger scale over the bulk of those waters.) These are both scale band 5, so to meet IHO standards this chart must be broken up. They cannot overlap, so that breaks up the region into two parts 5WA14 and 5WA18. Then we notice that RNC 18449 also overlaps RNC 18450, which is scale 1:10,000, which is also scale band 5, so it cannot overlap and has to be separated out. Thus we are building up the irregular rectangular shape of the ENC.

The same thing takes place to the south with overlapping 18448 and 18453, both also in scale band 5.  Note that the Port Orchard and Gig Harbor charts, which are also in scale band 5, are not cut out because they lie wholly within their respective ENC cells. They do not “overlap,” meaning part in and part out. Individual ENC charts are often referred to as "cells."

 * * *

We are left then with just two points raised in the first article, namely the confusion that might arise from the ENCs internal description of the corresponding RNC given for each ENC. These will always correspond to the name of the RNC that has the largest overlap with the ENC that is of the same scale. There will not often be a close correspondence, and in fact this formula for the internal description of the ENC can often be notably wrong, as in the case of US4WA.

OCS is aware of the confusion this might cause in some cases, and they are considering solutions. It is a big project, however, to name these more precisely. In principle, an algorithm could be written to make these names more realistic.  For now the key point for mariners is to simply understand this limitation when reading the ENC descriptions that their echart programs reproduce. They are not making this up, this is what the ENC says it is. 

 * * *

The other issue is the area of missing US ENC in waterway between Victoria and Race Passage, covered by US RNC 18465 or Canadian RNC 3440.  This waterway is all Canadian waters, which must have contributed to the results at hand.  But we still have the unique situation that an American vessel could sail from an American ENC of Haro Strait’s Canadian waters toward Race Passage and onto another US ENC, but have to cover up to 23 nmi without any US ENC. 

Sample of the NOAA Onliine Interactive Chart Viewer

It is not unprecedented that US ENC cover Canadian waters, but in this case we are forced to use the Canadian ENC, because of another IHO requirement that no two Nations can make an ENC of the same waters within the same scale band.  This means the US had to cut out a section (now the missing part) of the US ENC equivalent of 18465 (called US4WA34M) and mariners must now use Canadian ENC called CA470075. This was a direct conflict of overlapping scale bands (note the 4 in each chart name) from two nations, both of which had previous ENC of this region. This particular cell is now covered exclusively by Canada as a direct result of negotiations between the US and Canada about how they were going to meet the IHO standards along all of their long and complex common borders. In short, this is a compromise in these negotiations.

This situation stands out because many commercial vessels, as well as some racing yachts, prefer to use the same source of ENC, which is not possible in this unique case. We need the Canadian ENC of these waters, CA470075.

Individual Canadian ENC were not available in the past, but as of a month or so, they are in principle for sale. This one has a price of CND$25. It can be seen on Canadian Hydrographic Service  Interactive Chart Index, which is good way to view all of their charts, print and electronic… but save that link. It is hard to find.

Sample of Canadian Online Interactive Chart Viewer
I have purchased this Canadian ENC from our friends at Captains Nautical Supply and have documented the registration process, which is not entirely obvious. There are also there several videos on how to install the chart of a couple echart programs.

I would like to make a special thanks to Steve Soherr of the Customer Affairs Branch at NOAA's Office of Coast Survey. He has helped me and many others with charting and related questions many times over the years. The above notes, however, are my interpretation of the resources, and any misunderstanding or misstatements are my fault alone.

References on IHO requirements and US-Canadian ENC negotiations

The key acronym at IHO for the topic at hand is WEND (worldwide electronic navigational chart database). 

WEND Principles (from IHO)
Facts about Electronic Charts (from the IHO)
S-57 Interactive Object and Attribute Catalog (  Takes some patience, but it is all there!

The US-Canada agreement on ENC
The specific case of Pacific NW waters.

As noted earlier, the ENC format is still a bit in flux, but not to worry. It will soon be replaced with a new standard and much of this might change.  See S-101 Product Specification for the Electronic Navigational Chart