Which triangle or course ruler and which compass shape is the best? The question of the ideal set of tools for conventional navigation and chart work sparked a number of discussions following our navigation series (YACHT 12 to 16/2024). We have therefore decided to dedicate a separate article to this topic.
YACHT navigation series
Over time, I have accumulated a whole suitcase full of navigation tools in various designs. However, no clear favourite has emerged to date. Especially as there is nothing in this case that I would generally advise against. Every solution has its own advantages and pitfalls.
Of course I have personal preferences, but these are based more on subjective judgements: What am I most used to? What feels best for me? What am I most comfortable with? Everyone has to work out the answers to these questions for themselves.
Then there is the task for which the cutlery is to be used. Not everything that proves to be practical on land - for example when preparing for a driving licence test or when planning a cruise - is just as convincing on a lurching ship with strong heeling and occasional "buck jumps" in rough seas.
In terms of practical suitability, a distinction should also be made between reading out directions and drawing course and level lines. For the latter, you also need a pen - and therefore a free hand. The "one-handed suitability" of navigation equipment is therefore also an important aspect.
Basic equipment
Most of the so-called starter sets offered for driving licence training include a simple course triangle, a compass and a contact triangle. The contact triangle usually comes completely bare - without labelling and scales. This is a reasonable basic set to start with, but there is room for improvement. For example, I don't have a triangle at all. Instead, I usually use a regular course triangle for laying out and moving.
This has two advantages: Firstly, I always have a spare course triangle on board in case one breaks. Secondly, it gives me a bit more flexibility. Because I like to use course triangles in different sizes. The large version saves me having to repeatedly move it and allows me to cover long distances. The smaller triangle, on the other hand, is an advantage when working close to the edge of the map.
Ultimately, any straight edge is suitable for sliding - for example, a wooden strip or a simple school ruler. The only important thing is that the edge is absolutely straight and not too flat. I often also have a long ruler on the card table, especially when working with very large-format cards.
There are also special nautical rulers. The classic type are so-called parallel rulers, which are made up of two long individual rulers. Parallel rotating struts allow the two individual rulers to be moved parallel to each other. They are usually also marked with angles.
However, navigation triangles provide more accurate results when tracing and reading course angles, which is why they have overtaken the parallel ruler. And as a pure displacement tool, there are simpler and cheaper solutions. The good thing about high-quality parallel rulers is their considerable weight, which means they don't slip so easily.
Protractor
Course triangles are often referred to as "geometry triangles" by beginners because at first glance they are reminiscent of the protractors used in maths lessons. Even though both are right-angled and isosceles triangles with angles, there are clear differences between a geometric triangle and its nautical relatives. Firstly, there are the different angles: While the degree scale on a geometric triangle is 180 degrees, it is 360 degrees on a nautical triangle.
Of course, only half an arc can be depicted on a course triangle. Instead, there are two such arcs: one from 0 to 180 degrees and one from 180 to 360 degrees. The degrees on the two arcs are often coloured differently to make it easier to identify them - typically eastern directions in black and western directions in red.
There is also a different method of use. With a geo-triangle, the angle is usually first measured on the corresponding cathetus, i.e. on the short side, and the corresponding line is drawn in a second step, for which the triangle must be transposed. This step is not necessary with the price triangle, which is always created in such a way that its right angle tends to point downwards and the hypotenuse is at the top. This means that the price or level line can be drawn immediately after alignment.
Nevertheless, you could in principle also use a protractor to work with maps, although this requires a little more mental work in addition to the different handling. Additional computing power is required for angles over 180 degrees. What's more, even small navigation triangles are usually significantly larger than a standard geo-triangle. Finally, nautical charts are usually much larger than a DIN A4 sheet of paper used for drawing at school.
No absolute zero point
Nautical course triangles are available in various designs, which in turn fulfil different requirements. Opinions differ on the arrangement of the zero point. Some prefer course triangles with an external zero point, while others prefer an inwardly offset mooring point.
Beginners usually find it easier to work with an external zero point, as there is less confusion when positioning. This is because the alignment point is located exactly on the hypotenuse. Triangles with an internal zero point also have a zero mark on the hypotenuse, but this refers to the centimetre scale. However, the point at which the triangle is aligned with the meridian lies slightly below the hypotenuse. There is also a line running parallel to the hypotenuse through the zero point, which can be used to align the triangle with course lines.
This arrangement allows the triangle to be positioned more precisely. Especially as you do not necessarily have to look exactly at the edge of the triangle from above to ensure that it is positioned exactly. On the other hand, an error caused by using the wrong zero point can have a more critical effect than a slightly larger tolerance in the measurement accuracy. I would therefore always recommend using a triangle that you feel comfortable using.
Pointing the way
In addition, some triangles also offer assistance in determining the correct degree value. With two parallel degree scales, there are always two possible solutions. However, as the two numerical values are always 180 degrees apart, the correct assignment should not be too difficult as long as you have the compass rose reasonably well memorised - or at least the limits of the corresponding quadrants: 000°/360° = north, 090° = east, 180° = south, 270° = west.
A compass rose is also printed on almost every nautical chart. Many triangles also show the corresponding cardinal points in the colour of the respective degree scale, for example a black "NE" for north-east between the black degrees from 040° to 050°. Sometimes there are also coloured directional arrows on the hypotenuse: for example, a black arrow pointing "right" and a red arrow pointing "left". Depending on the direction in which the boat is moving, the similarly coloured degree values apply.
For use at sea, attention should be paid above all to a solid design. This is because the delicate tools made of transparent plastic have to withstand a lot. It is sometimes necessary to press the triangles firmly onto the map to prevent them from slipping. I have accidentally broken many a "lightweight" in the process. This happens particularly quickly with triangles that don't lie completely flat, but have nub-like feet on the underside. They are easier to move, which can also be an advantage. The only thing that helps here is to try it out for yourself to see which one works better.
Triangles with removable handles are very practical when travelling, as they are easier to stow away - for example, softly packed between the laundry. However, every hole in the triangle is also a potential breaking point. The same applies to holes for hanging and for marking ship types. In my experience, thick, monolithic constructions have proven to be the most stable. Some of the solid designs have been with me for decades.
Favourite triangular competitor
Some sailors prefer a so-called nautical plotter, also known as a "Portland plotter" or "Breton plotter", instead of a classic course triangle. No, this is not a digital chart plotter, but a completely analogue device. Basically, it is a special form of course ruler. It is said to have been invented by the Breton sailor Yvonnick Gueret in the 1960s. In the meantime, various versions of this protractor have been developed.
Common to all versions is a rotating disc with a degree or compass rose in the centre. Once the course ruler has been placed on the chart in the desired direction, the compass card is rotated until its north mark points exactly upwards. The correct angle can now be read off a zero mark next to the compass rose.
In addition to the zero point, many models also have a degree scale printed on them for the application of charges. The result is not read from the zero point, but from the relevant charge value.
One advantage is that there is only ever one result here - so you don't have to choose between two degree values. However, the course ruler must be positioned with the correct of the two long sides. An additional direction arrow on the ruler helps with this. It must point in the correct direction - i.e. in the case of a course line, in the direction in which the yacht is travelling across the chart.
North references
At the same time, it is important to align the rotating compass rose exactly to the north - for example to a meridian. Several parallel north references on the degree rose are very helpful. This allows it to be aligned even if its centre is not exactly on a meridian. If the north reference is designed as a grid, a latitude parallel can also be used for alignment if necessary. The number and spacing of these north references vary depending on the model. The more of them there are, the more flexibly the course ruler can be used.
However, the rose should not be mounted too loosely so that it does not slip in rough seas. It should also not be so rigid that both hands are needed to adjust it.
Some models also have small grip openings on the top of the compass card, such as the BRT-35 model from Run:Chart, which is, however, rather flabby. Even better is a solid swivel base, such as the very stable "Portland Course Plotter" from BH Navigation.
At first glance, such a "plotter" may appear somewhat bulky with its rectangular shape and impressive size. However, its size is also an advantage, as it means that the cutlery does not have to be moved frequently.
On the long arm
Protractors with a rotating arm are another variant of the course ruler. There are also various versions of these. The simplest consists of a simple thread attached to the centre of a compass rose. The thread is simply stretched in the direction to be measured and the number of degrees is then read off.
While this solution is only suitable for measuring directions, course and bearing lines can also be drawn on the edge of a rotating rigid arm. To do this, however, the centre of the degree rose in which the rotatable arm is mounted must be positioned exactly at the starting point of the course or bearing line - i.e. at the position of the starting point or the bearing object.
However, the course or stand line can then no longer be drawn through to this point because the base plate is in the way. It may have to be extended in an additional step. As with a nautical plotter, it is also important that the protractor is aligned exactly northwards. The transparent base plate has corresponding lines or a grid for the alternative use of a latitude parallel.
Finding a north reference at the starting point can be problematic on large-format maps with widely spaced grid lines. The KL-25-50 model from Run:Chart therefore comes with an auxiliary ruler for extending the north reference, but this again requires a second hand. For long course or level lines, a correspondingly long arm is also required, which makes the whole thing unwieldy. Especially as a long arm is more unstable and can easily break off. The arm of the KL-25-50 product can be folded out. This model also has separate references for standing and course lines, which on the other hand harbours the risk of confusion.
In the practical use of such course rulers at sea, it is always a certain challenge to fix the usually non-lockable and often bendable arm together with the base plate on the chart in the desired position in order to complete the relevant drawing work. In principle, there is little you can do wrong here - but working with such an instrument is not particularly practical.
Setting sail
The navigation set is completed by a course compass. Here, too, you may still have a copy from your school days in the drawer - but it should probably stay there. School compasses usually have a very fine point, which would puncture the charts and damage the chart table.
Although nautical compasses are also known as dividers despite their blunter tips, this is due to the fact that, unlike a school compass, they have two pointed ends. This means that there is no pencil lead at the drawing end, as the compass is not normally used for drawing.
It is mainly used to measure and measure distances. For longer distances, it is repeatedly rotated around the far end at a pre-set distance. Only when constructing circular bearing lines from distance measurements could a pencil end appear useful - but this is also unnecessary here, provided that the straight bearing line of the simultaneous bearing is drawn in first and the measured distance is then plotted on this.
Only for radar navigation do I occasionally have a compass with a pencil end on board, as several distance measurements sometimes provide a more accurate result than a bearing. For this purpose, the corresponding distance circles must actually be drawn "black on white" on the nautical chart.
Straight or curved?
With regard to the compass design, a distinction must be made between versions with and without a curve at the upper end. In compasses with curved legs, these cross in a similar way to scissors. This makes it easier to open the compass with one hand. This is not as easy with collapsible compasses with straight legs. On the other hand, the latter are considered somewhat more accurate because their tips are exactly opposite each other and not offset.
High-quality maritime compasses are usually made of brass - some are also chrome-plated. An adjusting screw at the upper end allows the ease of movement to be customised. Ideally, a compass should be easy to push together with one hand, but should not move again with every jolt through the ship. Here, too, it is important to try it out a little. Afterwards, you can then "set sail" wonderfully.
