Collection: Field Notes - Old Fashioned Seamanship

Series Hub: Traditional Navigation Techniques

The Sailing Kit for Navigation Without Electronics — Compass, Charts, Lead Line, Chip Log, Kamal, and Barometer

GPS will fail at the worst possible moment, for the simple reason that the worst possible moment is when you most need it and therefore when its failure matters most. The question is not whether to prepare for that moment but what preparation looks like in practice. This post is the inventory.

The answer is not complicated. It consists of a small number of instruments, most of which have been in use for centuries, which together cover every navigational function that GPS currently performs. Direction, speed, depth, position estimation, and weather monitoring. Without requiring power, satellites, or software. The total cost is modest. The total weight is negligible. The total volume fits comfortably in a chart table drawer.

This post is the gateway to the Old Fashioned Seamanship collection. The four series that follow it, Reading the Sea, Traditional Navigation Techniques, Weather Forecasting, and Passage Planning, cover the skills that make these instruments useful. This post covers the instruments themselves. What they are, what they do, and in some cases how to make them.

The series is not against GPS. It is against the assumption that GPS will always be available, and against the navigational helplessness that can follow when that assumption proves wrong.

The compass

The compass is the only item on this list you almost certainly already have, and it is the item most easily overlooked precisely because it is already there. A compass requires neither power nor satellites and works in fog, at night, in any weather. It requires periodic deviation-checking. A compass that has lived next to a handheld VHF for six months may have acquired deviation that its owner never verified. And it requires the discipline of actually using it as a primary instrument rather than as a backup check on the chartplotter.

One steering compass and one handheld bearing compass are the minimum useful combination. The steering compass is fixed and read underway. The handheld, a quality prismatic or Silva-type, is used for taking cross-bearings on landmarks, for checking the deviation of the steering compass by compass bearing of a transit, and as the backup if the steering compass is damaged or removed.

Compass care. Keep ferromagnetic objects away from the steering compass. Check deviation on the same bearing transits every season. Know your deviation card and have it on paper, laminated, attached to the chart table where it will survive a wave filling the cockpit.

If you want to learn star-based direction-finding without a magnetic compass at all, the Sidereal Compass app teaches the bearings of the practical stars on dry land.

Paper charts

Paper charts are the most important single item on this list. Every other instrument here is a tool for gathering information. The chart is where that information is interpreted. Without it, depth readings are numbers without context, compass courses lead nowhere in particular, and the DR plot has no surface to plot on.

The relevant chart coverage is straightforward. The waters you sail, at the appropriate scale. Passage charts at 1:200,000 or smaller for offshore work. Harbour and approach charts at 1:25,000 or larger for harbour entry. The Admiralty catalogue covers British and European waters comprehensively. Imray covers the same ground with slightly more sailor-specific detail.

Paper charts require maintenance. Notices to Mariners are issued weekly and chart corrections accumulate quickly in busy waters. A chart that has not been updated for two years may have wrong depths on a shifting bar, a new wreck mark, or a changed lighthouse character. The Admiralty Small Craft Charts and Imray charts are both produced with leisure sailors in mind and carry corrections as standard in their print run, but that print date still matters.

Waterproofing is not optional for any chart that will be used in a cockpit or in open conditions. The options. Dedicated chart cases, the simplest solution, giving immediate protection and quick access but the plastic will be there until the end of days. Or protect the paper with a few coats of shellac.

Plotting tools. A set of dividers, a parallel ruler or Douglas protractor, and a 2b pencil. These three items, with the chart, are enough to run a full dead reckoning plot. Nothing else is required.

The barometer

The barometer is the only weather instrument that gives direct continuous information about what the atmosphere is doing. Not what it is predicted to do. Not what it did at a weather station fifty miles away. What the pressure at your location is doing right now, and more importantly, how fast it is changing.

Pressure change rate is the key piece of information. Simon Rowell explains in Weather at Sea that a pressure fall of approximately one hectopascal per hour over several hours signals the approach of a frontal system. A fall of two hectopascals per hour or more is a deepening depression. A rise after a fall indicates the front has passed and the pressure gradient is now working in the opposite direction.

The barometer reading in isolation is less informative than the trend over three or six hours. A reading of 1010 hPa means very little by itself. A reading of 1010 hPa that was 1014 hPa three hours ago means a great deal. The habit of logging pressure at regular intervals, every three hours underway, every watch change on a longer passage, converts a barometer from a decoration into a weather instrument. Rowell describes this discipline as the foundation of any field forecast attempt. Without a logged pressure trend, you are guessing.

A good quality aneroid barometer, properly calibrated to sea level, is enough. Digital barographs that display pressure history are useful for visualising the trend but add no information a paper log does not provide. The expensive instrument is not necessary. The regular logging habit is.

What to look for. A steady pressure above 1013 hPa indicates settled anticyclonic conditions. Pressure below 1000 hPa indicates a significant low in the vicinity. A rapid fall, two or more hPa per hour, deserves immediate attention regardless of what the forecast said four hours ago. A rising pressure after a front, particularly a rapid rise, can indicate a fast-deepening low behind the front rather than settled conditions ahead. A rapid post-frontal rise followed by a renewed fall is one of the more dangerous North Atlantic weather sequences and the barometer is the only instrument that catches it in real time.

The full treatment of how to read a synoptic chart and what the barometer is telling you in context is in the Weather Forecasting series.

The lead line

A weighted line marked at depth intervals, with a cavity at the base of the lead filled with tallow to sample the seabed. Construction and use are covered in full in The Lead Line — Depth Sounding. The short version. A cast of the lead gives you two pieces of information at once. Depth, and bottom type. Together they place you on the chart with a precision no other instrument can match in the shallow tidal waters of the North Sea, Channel, and Baltic.

Making the lead. Two options. The traditional cast lead in a pear or cylindrical shape, with an arming cavity at the base and a ring eye at the top for the line. Or, the version I use, a length of M16 threaded bar stacked with nuts and washers to the required weight, which costs about ten pounds in materials and works equally well in the small-craft waters this collection addresses. The line. Hard-laid hemp or manila, twenty-five fathoms minimum, marked by feel in the traditional system or by coloured whippings in metric. The tallow or soft grease for arming. Any chandlery stocks proprietary arming compound. Ordinary tallow candle or cooking lard works.

The lead line will outlast every electronic instrument aboard.

The chip log

A piece of weighted wood, a length of marked line, and a timing mechanism. The chip log measures speed through the water, feeds the dead reckoning plot, and gives the origin of the word knot. The knotted intervals of line that ran out over the stern. Construction and use are covered in full in The Chip Log — Measuring Speed Over Water.

Making the chip. A quadrant-shaped piece of hardwood approximately fifteen to twenty centimetres on the straight edges, weighted along the curved edge with lead sheet or fishing weights. Three bridle lines from the three corners join at a point from which the log line runs. The log line itself is marked with knots at forty-seven feet three inches for a twenty-eight-second timing period, or at half that interval for fourteen seconds. A watch provides the timing.

Total materials cost is under ten pounds. A chip log properly made and calibrated against a known distance provides a speed input to the DR plot that is objective, repeatable, and independent of every electronic system aboard.

The Dead Reckoning trainer lets you practise integrating chip log readings into a DR plot on dry land before you take the system to sea. Useful as a calculator while learning the paper method.

The kamal

A piece of stiff card approximately five centimetres tall and ten centimetres wide, with a length of string about sixty to seventy centimetres long threaded through the centre and knotted at the card end. The string is held between the teeth. The board is aligned with Polaris at the top edge and the horizon at the bottom. The knot position relative to a calibration mark records latitude.

Construction and calibration are in full in Finding Your Latitude Without Instruments. The instrument Arab navigators used to cross the Indian Ocean, that Pacific navigators refined into the ey-ass measurement of Polaris height, that Tristan Gooley demonstrated with an Omani dhow crew during a passage described in How to Read Water, is made from card and string and costs nothing at all.

Calibrate it once at a known latitude by tying the knot at the position where Polaris exactly touches the top edge of the card. The instrument is then calibrated for that latitude. Sailing south and finding Polaris no longer reaches the card confirms southward movement. Sliding the knot outward to re-establish contact gives the new latitude by comparing knot positions.

The Sextant Navigation Trainer walks through the geometry of celestial sights on dry land and works as a calculator while you are learning. The kamal is simpler than a sextant. The mathematics is the same.

The logbook

Not an instrument in the same sense, but the item without which the others cannot function as a navigation system. The DR plot, the barometer trend, the log readings, the compass bearings, the depth soundings, the watch notes. None of these are navigational information until they are recorded in sequence and available for reference.

A dedicated logbook with columns for time, position or DR position, course, speed, weather, barometric pressure, and notes is the minimum. A waterproof cover or a sealed plastic bag around a standard notebook is adequate. The entries do not need to be elegant. They need to be regular, honest, and legible under motion.

The logbook is also the instrument that most honestly reveals the difference between a navigator who is running a dead reckoning plot and one who is following a GPS track and calling it navigation. The navigator running a DR plot fills pages. The navigator following GPS has nothing to write.

Putting it together

These six items. Compass, paper charts, barometer, lead line, chip log, and kamal, with plotting tools and a logbook. They are the physical kit that enables everything in the Old Fashioned Seamanship collection. None of them require power. None of them fail when GPS fails. None of them demand recalibration after a software update. Together they cover the full navigational range of direction, speed, depth, latitude, weather monitoring, and the surface-based observation that the four series in this collection build on.

The series that fill in the skills behind the kit:

Reading the Sea the Old Fashioned Way. Tidal current, swell, waves, water colour, night reading, foreshore, and the Beaufort scale as an observation tool.

Traditional Navigation Techniques. Star compass, etak, dead reckoning, land signs, latitude, chip log, and lead line in full.

Weather Forecasting. The synoptic chart, Atlantic depressions, why forecasts fail on terrain-influenced water, field forecasting from cloud and barometer.

Coastal and Offshore Passage Planning. The North Sea, Biscay, and the go/no-go decision framework.

References

Lewis, D. (1994). We, the Navigators: The Ancient Art of Landfinding in the Pacific. University of Hawai'i Press.

Gooley, T. (2016). How to Read Water  Sceptre.

Rowell, S. (2020). Weather at Sea: A Cruising Skipper's Guide to the Weather. Fernhurst Books. 

Woodmencey, J. (2022). Reading Weather: The Field Guide to Forecasting the Weather. Falcon Guides.

Dye, F. and Dye, M. (1977). Ocean Crossing Wayfarer. David and Charles.

At VAKA I design and build boats that don't destroy the environment. Find the plans as they are finalised at VAKA Plans and the full field notes here. If you are looking for a launching spot, the Hithe Finder is a community register of slipways, hards, and beaches for small boats.

VAKA. Traditional craft and natural materials. Nottingham. 2026.