Monday, 10 August 2026

Making the Best Use of a Long Lens


 

Making the Best Use of a Long Lens

There is something rather magical about a long camera lens.

It allows us to photograph a bird on the far side of a field, isolate a sailing boat from a busy background, pick out details on a distant building, photograph wildlife without approaching too closely, or compress a landscape so that distant objects appear almost stacked together.

My own interest in long lenses goes back a very long way.

As a teenager, I started photography with a Zenit E — about the most sophisticated camera I could afford at the age of 13. Compared with modern digital cameras it was extraordinarily basic. There was no autofocus, no image stabilisation, no automatic ISO and certainly no ability to take twenty or thirty frames every second and decide afterwards which one was sharp.

But there was one considerable advantage.

Occasionally I could borrow my father's 300mm f/2.8 lens.

To a young photographer, that lens seemed enormous.

Sometimes I could even add a 2x teleconverter — or "doubler", as we tended to call it — effectively turning the combination into a 600mm f/5.6 lens.

Suddenly birds and other distant objects that had previously been little more than dots in the viewfinder became possible photographic subjects.

That experience taught me something that remains true today:

Having a long lens opens photographic opportunities — but owning the lens is only the beginning.

From a Zenit E to Modern Super-Telephoto Zooms

Photography equipment has changed enormously since those days.

Today I have a much more flexible collection of long lenses, including a fast 70-210mm f/2.8 and a Sigma 150-600mm.

Like many photographers, I have gradually moved away from relying heavily on fixed focal-length telephoto lenses towards zoom lenses.

There are still excellent reasons for using prime lenses. A high-quality 300mm, 400mm or 600mm prime can provide exceptional sharpness, wide maximum apertures and excellent autofocus performance.

But zoom lenses offer something incredibly useful in real-world photography:

flexibility.

With a 150-600mm zoom, for example, I can photograph a sailing boat approaching from some distance at 600mm, then zoom back towards 300mm or 200mm as it gets closer.

With wildlife, I can photograph a bird perched some distance away and then instantly change the framing if it takes off and flies towards me.

That is much harder when using a fixed focal-length lens.

For the sort of photography I do, that flexibility frequently matters more than achieving the absolute theoretical maximum image quality.

What Does a Long Lens Actually Do?

We often describe telephoto lenses as "magnifying" distant objects.

That is a useful everyday description, but technically the important change is the lens's angle of view.

A 600mm lens sees a much narrower angle than a 50mm lens.

Because the camera is recording a smaller section of the scene, distant objects occupy much more of the image.

This produces the impression that we have moved closer to the subject.

It is enormously useful for subjects such as:

  • birds;

  • wildlife;

  • sailing;

  • aircraft;

  • motorsport;

  • astronomy;

  • distant landscapes;

  • architectural details;

  • sports;

  • events where the photographer cannot physically approach the subject.

But the narrow field of view also creates challenges.

At 600mm, finding a flying bird in the viewfinder can be surprisingly difficult.

A tiny movement of the camera produces a much larger apparent movement of the subject in the image.

Long-lens photography therefore becomes partly about learning how to control the camera.

Does a Smaller Sensor Give More Magnification?

This is one area where photographic terminology can become confusing.

If I fit my 600mm lens to a smaller-sensor DSLR, the lens itself does not suddenly become optically more powerful.

A 600mm lens remains a 600mm lens.

However, the smaller sensor records a smaller central portion of the image produced by the lens.

The result is a narrower field of view.

For example, on a camera with a 1.6x crop factor:

600mm x 1.6 = 960mm

We would therefore describe the resulting field of view as being equivalent to approximately 960mm on a full-frame camera.

That can be extremely useful for bird and wildlife photography because the subject occupies a larger proportion of the recorded frame.

But it is worth making the distinction.

The crop sensor has not changed the focal length of the lens.

It has changed how much of the lens's image circle is being recorded.

Why Long Lenses Need Good Technique

A long lens magnifies something else as well as the subject:

camera movement.

This is why photographs taken with telephoto lenses can sometimes look slightly soft even when the lens itself is extremely sharp.

At short focal lengths, a small movement of the camera might barely be visible.

At 600mm, the same movement can ruin the photograph.

Traditionally, photographers used the reciprocal rule as a rough guide:

Minimum shutter speed = approximately 1 / focal length

So with a 500mm lens, we might start thinking about something around 1/500 second.

But this is only a starting point.

Modern high-resolution cameras, moving subjects and crop sensors often mean using considerably faster shutter speeds.

For birds in flight I might prefer something such as:

1/1000 second

1/1600 second

1/2000 second

or faster.

For very fast wing movement, even 1/3200 second may be useful.

Modern image stabilisation is excellent, but stabilisation cannot freeze a moving bird.

It compensates for camera movement.

Shutter speed still has to deal with subject movement.

A Fast Aperture Is Extremely Valuable

This is one reason that my father's old 300mm f/2.8 was such an impressive lens.

An aperture of f/2.8 on a 300mm lens allows a large amount of light into the camera.

That means faster shutter speeds are possible in poor light.

It can also produce beautifully blurred backgrounds.

The problem is that large-aperture telephoto lenses require very large pieces of precision optical glass.

That makes them:

  • large;

  • heavy;

  • technically difficult to manufacture;

  • and expensive.

There is a considerable physical difference between producing a 300mm f/2.8 lens and producing a much smaller-aperture 300mm lens.

The front element alone gives a clue to what is required.

A rough relationship is:

Aperture diameter = focal length / f-number

For a 300mm f/2.8 lens:

300 / 2.8 = approximately 107mm

That helps explain why fast professional telephoto lenses become so physically large.

Teleconverters: More Reach, But Not for Free

A teleconverter can still be extremely useful.

A 2x teleconverter doubles the effective focal length.

So:

300mm becomes 600mm

400mm becomes 800mm

600mm becomes 1200mm

But there is a price.

A 2x teleconverter normally costs about two stops of light.

So:

300mm f/2.8 becomes approximately 600mm f/5.6

The converter may also reduce autofocus performance and slightly reduce image quality.

Whether it is worthwhile therefore depends upon the lens, camera and subject.

With a high-quality fast prime lens, the result can be excellent.

Putting a teleconverter behind an already slow or relatively soft lens may be much less successful.

Why 150-600mm Zooms Are So Useful

For many photographers, the modern 150-600mm zoom occupies a very interesting position.

It gives enormous photographic reach without entering the cost, weight and specialist nature of the very large professional prime lenses.

At 150mm I can still frame a fairly large subject.

At 600mm I can photograph something much further away.

That range is particularly useful when photographing unpredictable subjects.

Imagine photographing sailing.

A boat might be hundreds of metres away as it approaches a mark.

At that point, 500mm or 600mm might produce the photograph I want.

A few moments later the same boat could pass fairly close to the camera.

Now perhaps 200mm is more appropriate.

With a zoom I can follow the action continuously.

That is one of the reasons zooms have become such practical working tools.

Do Not Automatically Use the Longest Focal Length

One of the easiest mistakes is assuming:

"If I have 600mm available, I should use 600mm."

Not necessarily.

Sometimes 400mm will produce the better photograph.

Sometimes 250mm will.

The important question is not:

"How much focal length have I got?"

It is:

"What composition am I trying to create?"

A bird completely filling the frame may make an excellent identification photograph.

But a smaller bird surrounded by reeds, branches or water may make a much more interesting environmental portrait.

Similarly, a photograph of a yacht filling almost the entire frame can be impressive.

But sometimes including the river, competing boats, spectators and surrounding landscape tells a better story.

The lens should serve the photograph rather than dominate it.

Long Lenses Change the Appearance of Perspective

Telephoto lenses can also create a very distinctive visual effect known as perspective compression.

Strictly speaking, perspective itself is determined by the photographer's position.

But because we normally stand much further away when using long lenses, objects at different distances can appear much closer together in the final image.

A row of sailing boats may appear tightly packed.

Hills behind a town may appear dramatically large.

The Moon near a building can appear enormous.

A distant bridge may seem surprisingly close to the subject in front of it.

This is not simply about photographing distant things.

It can be an important creative technique.

Atmospheric Conditions Become Part of the Optical System

There is another limitation that buying a more expensive lens cannot solve.

The atmosphere.

At very long distances, we are photographing through a considerable amount of air.

That air may contain:

  • water vapour;

  • dust;

  • pollen;

  • pollution;

  • turbulence;

  • heat gradients.

On a warm day, heat shimmer can destroy fine detail.

You may have an extraordinarily expensive lens perfectly focused on a distant subject and still obtain a slightly wobbly-looking photograph.

The problem is not the camera.

You are effectively photographing through moving layers of air with slightly different refractive properties.

Early mornings are often better for extreme long-distance photography because the atmosphere tends to be cooler and more stable.

This is particularly noticeable with wildlife, aircraft, landscape and astronomical photography.

Supporting the Lens Properly

A 150-600mm lens is not something I particularly want hanging unsupported from my hands all day.

There are several possibilities.

Handheld

Modern stabilisation makes handheld super-telephoto photography surprisingly practical.

It also provides enormous freedom for tracking birds and moving subjects.

Good posture makes a significant difference.

Keep the elbows relatively close to the body.

Support the lens under its centre of gravity.

Avoid holding your breath for long periods; instead, settle your breathing and release the shutter smoothly.

Monopod

A monopod is one of my favourite compromises.

It removes much of the weight while still allowing the camera to move quickly.

That can be ideal for sport, sailing and wildlife.

Tripod

For static subjects or very long periods in one location, a tripod becomes extremely useful.

Heavy long lenses benefit particularly from a gimbal-style head because the camera can remain balanced while still moving freely.

The key is not simply preventing movement.

It is making the entire camera-and-lens combination comfortable enough that I can concentrate on photography.

Finding the Subject at 600mm

Anyone who has tried photographing a bird in flight with a super-telephoto lens will know the problem.

You see the bird.

You raise the camera.

You look through the viewfinder.

Nothing.

At 600mm the field of view is so narrow that it is surprisingly easy to point the lens slightly to one side of the subject.

A good technique is to initially locate the bird at a shorter focal length.

Perhaps start around 200mm or 300mm.

Acquire the subject.

Then zoom towards 500mm or 600mm while continuing to track it.

With practice, locating subjects becomes much faster.

But it is a learned skill.

Autofocus Settings Matter

Modern cameras have transformed long-lens photography.

Subject recognition, animal-eye autofocus and sophisticated tracking systems can make photographs possible that would have been extremely difficult when I first started.

But the photographer still needs to understand what the autofocus system is doing.

For a perched bird, a relatively precise autofocus area may be appropriate.

For a bird in flight, continuous autofocus and subject tracking may work much better.

For sailing, I might use tracking autofocus to keep the boat or crew sharp while panning.

The important point is to experiment with the camera before the important event.

The middle of a sailing race is not the ideal moment to start discovering what an unfamiliar autofocus mode actually does.

Exposure Becomes a Balancing Act

Long-lens wildlife and sports photography often requires a compromise between three things:

  • shutter speed;

  • aperture;

  • ISO.

Suppose I am photographing a bird in flight.

I might want:

1/2000 second

The lens might be at:

f/6.3

The camera then has to use whatever ISO is necessary to produce the correct exposure.

Years ago I would have worried considerably about raising ISO.

Modern cameras handle higher ISO settings remarkably well.

I would usually rather have:

a sharp photograph with some noise

than:

a beautifully noise-free photograph ruined by motion blur.

Noise can often be reduced afterwards.

Motion blur usually cannot.

Long Lenses Are Not Only for Wildlife

Wildlife is perhaps the obvious use, but long lenses have many applications.

Sailing photography

Long lenses allow me to photograph boats from the bank or another boat without needing to be immediately beside the action.

They are excellent for:

  • starts;

  • mark roundings;

  • crew expressions;

  • sail details;

  • close racing;

  • spray and water;

  • isolated action photographs.

Landscape photography

Telephotos can extract small compositions from huge landscapes.

Instead of photographing the entire scene, I might pick out:

  • a distant tree;

  • layers of hills;

  • a church tower;

  • sunlight hitting one field;

  • mist in a valley.

Garden photography

Long lenses can even be useful relatively close to home.

Photographing birds at a feeder from some distance away reduces disturbance.

A long focal length can also create beautifully soft backgrounds.

The Moon

The Moon is a wonderful long-lens subject.

Even 600mm will show a surprising amount of detail.

Using a crop-sensor camera can make the Moon fill even more of the frame.

Details We Normally Miss

Perhaps most interestingly, a long lens trains us to notice things.

A distant architectural feature.

An insect-eating bird on a television aerial.

A face in a crowd.

Rigging on a sailing boat.

Patterns on a distant hillside.

Photography becomes a form of observation.

The Temptation to Buy Ever Longer Lenses

There is always another lens.

If 600mm is useful, then surely 800mm must be better.

And if 800mm is useful, perhaps 1200mm would be even better.

Eventually the economics become rather uncomfortable.

Very long professional lenses can be extraordinarily expensive.

They can also be enormous and heavy.

Before purchasing specialist equipment, I think it is worth asking some very practical questions.

What will I photograph with it?

How often will I use it?

Could I hire one when necessary?

Would a teleconverter be sufficient?

Would a crop-sensor body give me the framing I need?

Could I simply move closer?

Would better fieldcraft produce a bigger improvement than another 200mm of focal length?

And, particularly for professional or company photography:

How will the equipment repay its investment?

Equipment Has to Earn Its Place

This becomes particularly important when photography forms part of a business.

It is very easy to admire an £8,000, £10,000 or even more expensive lens.

But an impressive specification does not automatically make it a sensible business purchase.

Suppose an expensive lens allows me to photograph a specialist event that produces commercial work.

Perhaps it contributes to:

  • commissioned photography;

  • stock photography;

  • educational material;

  • YouTube videos;

  • promotional images;

  • magazine work;

  • sailing coverage;

  • wildlife projects.

Then the investment may make sense.

But if it spends 360 days each year sitting in a cupboard, hiring it for the remaining five days might have been much more sensible.

Photography equipment should enable projects.

The project should not exist merely to justify buying the equipment.

Sometimes Better Technique Beats More Equipment

This is perhaps the most important lesson.

A photographer with a 600mm lens who understands light, movement, autofocus, composition and animal behaviour can produce extraordinary photographs.

Someone with an even more expensive 800mm lens who simply points it towards the subject may not.

Improving technique costs remarkably little.

Learn when the birds visit.

Learn where the sailing boats will round the mark.

Notice where the sunlight will come from.

Choose the background before the subject arrives.

Practise tracking.

Experiment with shutter speed.

Understand the autofocus system.

Find a stable shooting position.

Long-lens photography is partly about optics.

But it is equally about anticipation.

From Film Photography to Thousands of Digital Frames

When I think back to that Zenit E, the contrast with modern photography is extraordinary.

Every frame of film cost money.

There was no screen on the back of the camera.

I could not enlarge the photograph immediately to check the focus.

I could not simply increase the ISO for the next frame.

Autofocus did not find a bird's eye.

Image stabilisation did not compensate for camera shake.

Yet those limitations were also valuable.

They forced me to think carefully about each photograph.

Digital technology has made photography enormously more capable, but I still think there is something worth retaining from those early days:

Think before pressing the shutter.

What am I photographing?

Why am I photographing it?

Where is the light?

What is in the background?

What shutter speed do I need?

What will happen next?

Those questions matter more than whether the lens is 400mm, 600mm or 1200mm.

Conclusion: Reach Is Useful — Seeing Is More Important

Long lenses give photographers an extraordinary ability to explore parts of the world that would otherwise remain visually distant.

From borrowing my father's 300mm f/2.8 as a teenager with a Zenit E to using modern super-telephoto zoom lenses today, the technology has changed dramatically.

Modern cameras provide autofocus, stabilisation, huge usable ISO ranges, crop-sensor options and lenses such as the 150-600mm that offer a degree of flexibility I could scarcely have imagined when I started.

But the fundamental challenge remains remarkably similar.

The best long-lens photograph still depends upon being in the right place, understanding the subject, controlling movement, noticing the light and anticipating what is about to happen.

And perhaps that is why I still enjoy long-lens photography.

A telephoto lens does more than make distant subjects appear closer.

It encourages us to look more carefully at things that are normally too far away to notice.

Sunday, 9 August 2026

Learning New Skills on the OAX Pergamon

 

Learning New Skills on the OAX Pergamon

It is easy to think of an organ simply as an instrument for playing music. However, a modern instrument such as the OAX Pergamon is much more than that. It is a complete creative workstation, capable of producing everything from traditional organ music to orchestral arrangements, atmospheric film soundtracks and entirely new synthesised sounds.

For Philip M Russell Ltd, the organ forms an important part of the company’s creative toolkit. It can support video production, educational content, sailing films, science demonstrations and other media projects. However, having access to a sophisticated instrument is only the beginning. The real challenge is learning how to use it effectively.

That means improving my playing technique, understanding registrations, arranging music, experimenting with sound design and gradually developing the confidence to turn musical ideas into finished recordings.

More Than Just Learning to Play Notes

When learning a new piece of music, it is tempting to concentrate entirely on playing the correct notes. That is certainly important, but it is only one part of making a performance sound convincing.

A successful performance also depends on:

  • rhythm and timing;

  • phrasing;

  • dynamics;

  • choice of sounds;

  • balance between the keyboards;

  • effective use of the pedals;

  • and the emotional character of the music.

A piece can be technically correct and still sound rather lifeless. Equally, a relatively simple arrangement can become powerful when it is played with confidence and given an appropriate selection of sounds.

This is one of the reasons I find the OAX Pergamon so interesting. It encourages me to think not only as a keyboard player, but also as an arranger, sound designer and producer.

Developing Better Playing Technique

The first area I am continuing to develop is basic playing technique.

Even with electronic assistance, automatic accompaniment and carefully prepared registrations, there is no substitute for being able to play accurately and consistently. Improving technique makes it easier to concentrate on expression rather than worrying about where the next note is.

My practice includes working on several different skills.

Playing the Keyboards Independently

The Pergamon has multiple manuals, allowing different sounds and musical parts to be played at the same time.

For example:

  • the lower keyboard might carry strings or a rhythmic accompaniment;

  • the middle keyboard might contain piano, brass or orchestral sounds;

  • the upper keyboard might provide a solo instrument;

  • and the pedals might control the bass line.

Learning to use the keyboards independently requires coordination. It is rather like asking several musicians to perform together, except that one person is responsible for all of them.

I have found that it helps to practise each part separately before combining them. I might begin with the melody, then add the left-hand chords and finally introduce the pedals. Slowing the music down often reveals mistakes that can be hidden when attempting to play too quickly.

Improving Pedal Technique

The pedalboard adds another dimension to the instrument. It allows the player to create a strong bass line, but it also requires the feet to operate independently from the hands.

At first, it can be difficult to resist looking down at the pedals. The longer-term aim is to develop a physical awareness of where the notes are, just as a pianist learns to find keys without constantly watching their hands.

Short exercises are often more useful than repeatedly attempting an entire piece. Practising simple bass patterns, scales and chord roots helps to build accuracy and confidence.

Controlling Timing and Expression

Playing every note at exactly the same volume and length can make music sound mechanical. A musical performance needs shape.

This may involve:

  • allowing a melody to breathe;

  • emphasising important notes;

  • slightly relaxing the tempo at the end of a phrase;

  • building towards a climax;

  • or making one musical line stand out from the others.

These details are difficult to achieve while still struggling with the notes. As technique improves, more attention can be given to the character of the performance.

Understanding Registrations

One of the most powerful features of the OAX system is its ability to combine and control a large range of sounds. The particular combination of sounds used for a piece is often described as a registration.

Choosing a registration is rather like selecting the instruments for an orchestra.

A melody might be played using:

  • a trumpet;

  • a violin;

  • a saxophone;

  • a traditional organ stop;

  • a synthesiser lead;

  • or a completely new layered sound.

Each choice changes the character of the music.

Matching Sounds to the Music

The registration needs to suit the style and purpose of the piece.

A traditional hymn might use pipe-organ sounds, while a cinematic arrangement could combine strings, French horns, percussion and a deep synthesised bass. A gentle nature video might require piano, flute and soft atmospheric pads. A sailing film might benefit from brass, strings and percussion to create a sense of movement and adventure.

The most impressive sound is not always the best choice. A large orchestral registration can overwhelm a quiet melody, while a simple piano or flute sound may communicate the idea far more effectively.

Learning to create registrations therefore involves restraint as well as imagination.

Balancing the Different Parts

When several sounds are layered together, balance becomes essential.

A solo instrument needs to be loud enough to carry the melody, but not so loud that it feels disconnected from the accompaniment. Bass sounds must provide weight without making the recording muddy. Strings can add warmth, but too many layers can hide the detail of the performance.

This is where the organ begins to overlap with music production. The player has to consider volume, frequency, stereo position, effects and the relationship between individual musical parts.

Sometimes the solution is not to add another sound, but to remove one.

Saving Registrations for Future Performances

A carefully designed registration can take considerable time to create. Once it is working well, it makes sense to save it.

This provides several advantages:

  • the same arrangement can be recalled quickly;

  • recordings can be repeated more consistently;

  • changes can be compared;

  • and successful sound combinations can be adapted for future projects.

Over time, this creates a personal library of musical starting points. Instead of beginning every project with a blank instrument, I can begin with a registration that already captures the general mood I want.

Arranging Music for Films and Videos

One of the most useful applications of the Pergamon is creating original music for video.

Music can completely change the way an audience responds to an image. The same sailing footage can feel peaceful, exciting, nostalgic or dramatic depending on the soundtrack.

For example, a film showing Champagne, our Thames A-Rater, moving slowly along the river might use gentle piano and strings. Footage from a fast race could use percussion, brass and rhythmic synthesiser sounds. A restoration video might begin quietly and gradually build as the work progresses.

The music does not merely sit behind the pictures. It helps tell the story.

Starting with the Mood

Before arranging music for a film, I need to decide what the audience should feel.

Is the scene:

  • exciting;

  • reflective;

  • tense;

  • humorous;

  • mysterious;

  • educational;

  • or triumphant?

Once the mood is clear, it becomes easier to choose the tempo, key, instruments and structure.

A slow tempo with sustained chords may create calm or reflection. A faster pulse can suggest movement and energy. Repeated low notes can create tension, while rising harmonies can give a sense of progress or achievement.

Writing Music Around the Pictures

Music for film often needs to follow the timing of the video.

Important moments might include:

  • a boat leaving the pontoon;

  • the sails filling with wind;

  • the start of a race;

  • a science experiment producing a visible result;

  • a laser cutter beginning its work;

  • or a completed project being revealed.

The music can build towards these moments and then change when they occur.

This requires a different approach from simply playing a piece from beginning to end. The arrangement may need to be extended, shortened or reorganised to match the images.

Sometimes a musical phrase needs to last a few seconds longer. At other times, a dramatic chord needs to arrive at a precise point in the film.

This creates a close connection between the organ, the digital audio workstation and the video-editing process.

Connecting the Organ with a DAW

The OAX Pergamon can become even more versatile when it is linked to a digital audio workstation, or DAW.

The DAW can be used to:

  • record MIDI performances;

  • edit incorrect notes;

  • adjust timing;

  • add virtual instruments;

  • create multiple tracks;

  • apply effects;

  • balance the final mix;

  • and synchronise music with video.

This does not mean removing the human performance. Instead, it allows the performance to be refined.

For example, I can record the main keyboard part on the Pergamon, then add another layer using a virtual instrument. I might use the organ for the initial orchestral arrangement and then add percussion, sound effects or additional synthesiser textures in the DAW.

The organ provides the immediacy of live performance, while the DAW provides detailed control.

Experimenting with VST Instruments

Virtual Studio Technology instruments, usually known as VSTs, make it possible to extend the available range of sounds.

These may include:

  • detailed pipe organs;

  • concert pianos;

  • orchestral instruments;

  • synthesisers;

  • choirs;

  • cinematic percussion;

  • and unusual experimental sounds.

Connecting these instruments to the Pergamon can sometimes be technically challenging. Software has to be installed correctly, MIDI routing must be configured and the computer must be able to run the instruments reliably.

There can be moments when the process feels more like computing than music. However, once everything is working, the creative possibilities increase enormously.

A single keyboard can control an instrument that has been sampled from a concert hall, cathedral, synthesiser studio or full orchestra.

Synthesising New Sounds

Not every sound has to imitate an existing musical instrument.

Sound synthesis makes it possible to create something entirely new.

A sound can be built by changing:

  • the waveform;

  • attack;

  • decay;

  • sustain;

  • release;

  • filters;

  • modulation;

  • pitch movement;

  • reverb;

  • delay;

  • and many other parameters.

Even small adjustments can have a dramatic effect.

A sharp, fast attack might produce a plucked or percussive sound. A slow attack can create a soft pad that gradually appears behind the music. Filtering can turn a bright sound into something warmer and more distant. Modulation can add movement and prevent a sustained note from feeling static.

This is particularly useful for film music because an original sound can help give a project its own identity.

For a science video, I might create a precise electronic pulse. For a microscopic nature film, I could use delicate, shimmering tones. For a sailing sequence, I might design a broad, moving sound that suggests wind, water and open space.

Learning Through Experimentation

Not every experiment produces a useful result.

Some registrations become too complicated. Some sound combinations compete with each other. Some arrangements work well on the organ but become cluttered when recorded. A synthesised sound may be interesting on its own but unsuitable for the finished film.

However, these unsuccessful experiments are still valuable.

They help answer questions such as:

  • Which sounds work well together?

  • How many layers are really necessary?

  • Why does a mix sound muddy?

  • What makes a melody stand out?

  • How much reverb is too much?

  • When should a musical arrangement remain simple?

The more I experiment, the easier it becomes to recognise what is likely to work.

Building Musical Confidence

Musical confidence does not arrive suddenly. It develops through repeated small successes.

It grows when I can play a difficult passage more accurately than I could the week before. It grows when a registration begins to sound convincing. It grows when music fits a video and gives the images more emotional impact.

Recording performances can be uncomfortable because every hesitation and error becomes obvious. However, recording is also one of the best ways to improve.

Listening back reveals things that are difficult to notice while playing:

  • uneven timing;

  • notes that are too loud;

  • awkward transitions;

  • overcomplicated arrangements;

  • or sections that need more expression.

The aim is not perfection. The aim is progress.

A Practical Learning Routine

A useful practice session does not need to involve playing for several hours. A focused routine can be more productive.

A typical session might include:

Ten minutes of technique

Scales, chords, pedal exercises or coordination between the manuals.

Fifteen minutes on a piece

Concentrating on one difficult section rather than repeatedly playing the entire arrangement.

Fifteen minutes on registrations

Testing instrument combinations, adjusting levels and saving useful settings.

Ten minutes of improvisation

Experimenting freely with melodies, chords and sounds.

Ten minutes of recording and review

Recording a short performance, listening back and identifying one or two areas for improvement.

This creates a balance between discipline and creativity.

Music as Part of the Company’s Wider Work

The OAX Pergamon is not an isolated hobby. It connects with many other areas of the company.

Original music can be created for:

  • science experiment videos;

  • educational introductions;

  • YouTube programmes;

  • sailing films;

  • restoration projects;

  • timelapse photography;

  • promotional videos;

  • and social media content.

Producing music internally also allows the soundtrack to be shaped specifically around the project. The music can reflect the pace, character and visual style of the film rather than relying on a generic track.

It also gives the company another opportunity to develop original intellectual and creative work.

The Value of Continuing to Learn

One of the most rewarding aspects of owning a sophisticated instrument is knowing that there is always something new to discover.

There are new techniques to practise, registrations to build, VST instruments to explore, sounds to design and arrangements to create.

At times, the amount of technology can feel overwhelming. It is possible to spend a great deal of time changing settings without actually making music. The challenge is to ensure that the technology supports the creative process rather than becoming the entire process.

I am learning that the best results often come from combining three things:

  • a clear musical idea;

  • a manageable selection of sounds;

  • and enough technical knowledge to turn the idea into a finished recording.

Conclusion: Turning an Instrument into a Creative Workshop

Learning the OAX Pergamon is not simply about becoming a better organ player. It is about developing a broader range of creative skills.

It involves musicianship, arrangement, sound design, recording, computing and film production. Each new skill strengthens the others.

Improved playing technique makes arrangements more convincing. Better registrations make performances more expressive. Knowledge of the DAW makes recordings easier to refine. Sound synthesis creates new possibilities for films and videos.

Most importantly, the process builds confidence.

The Pergamon is capable of producing an extraordinary range of music, but its real potential is only revealed gradually, through practice, experimentation and a willingness to keep learning.

For Philip M Russell Ltd, it is becoming more than an organ. It is a musical workshop, a sound-design laboratory and an increasingly important part of the company’s creative production process.


Saturday, 8 August 2026

IRPCS for Sailors: Who Gives Way, Who Stands On and What Happens in a Narrow Channel?


 

IRPCS for Sailors: Who Gives Way, Who Stands On and What Happens in a Narrow Channel?

Sailing would be much simpler if we always had the river, lake or sea to ourselves. In reality, we share the water with other sailing boats, motor cruisers, rowing boats, paddleboards, safety boats, commercial vessels and sometimes boats whose intentions are far from obvious.

That is where the International Regulations for Preventing Collisions at Sea come in.

Usually known as the IRPCS or COLREGs, these regulations provide a common set of expectations. They help vessels behave predictably when they meet, cross or overtake one another.

However, the rules are not simply a hierarchy that gives one boat an absolute “right of way”. They are a system for preventing collisions. Even the stand-on vessel must remain alert and may eventually be required to act.

For those of us learning to sail on a comparatively narrow and busy river, this is particularly important. A sailing boat may theoretically be the stand-on vessel in one situation, but its skipper must still consider the riverbank, moored boats, bridges, other traffic, wind shadows and whether a larger vessel has enough room to manoeuvre.

The real objective is not to prove that we were correct.

The objective is to avoid the collision.

What Are the IRPCS?

The IRPCS are the International Regulations for Preventing Collisions at Sea. They are also commonly called the Collision Regulations or COLREGs.

They cover subjects including:

  • maintaining a proper lookout;

  • travelling at a safe speed;

  • assessing the risk of collision;

  • actions to avoid collision;

  • sailing vessels meeting one another;

  • overtaking;

  • crossing situations;

  • narrow channels;

  • responsibilities between different types of vessel;

  • navigation lights, shapes and sound signals.

UK guidance confirms that vessels and watercraft operating at sea, or in waters connected to the sea and navigable by seagoing vessels, must comply with the Collision Regulations. Authorities can also make special rules for harbours, rivers, lakes and inland waterways.

This distinction matters on the Thames. The non-tidal River Thames is governed by Environment Agency navigation byelaws, which contain rules closely related to the IRPCS but adapted to the river environment. Local restrictions, event directions, bridge instructions and navigation notices must also be followed.

The Most Important Rule Comes Before “Who Gives Way?”

Before deciding whether another vessel must give way, we must first decide whether a risk of collision exists.

Four fundamental principles apply to almost every encounter.

Maintain a Proper Lookout

Every vessel must maintain a proper lookout by sight, hearing and any other appropriate means available.

On a small sailing boat, this means more than looking straight ahead. The helm and crew should regularly look:

  • ahead and to leeward;

  • behind the mainsail and jib;

  • astern for overtaking vessels;

  • towards side channels and moorings;

  • around bends;

  • through bridge arches;

  • towards boats that may be hidden by other traffic.

A large sail can create a significant blind spot. Moving one’s head, changing position briefly or asking a crew member to check the obscured side can reveal a boat that would otherwise remain invisible.

Travel at a Safe Speed

A safe speed is not necessarily the maximum speed permitted.

It is a speed at which the vessel can take effective avoiding action and, where appropriate, stop within a suitable distance.

The correct speed depends on visibility, traffic, available water, the vessel’s manoeuvrability, wind, current and nearby hazards. The IMO places proper lookout, safe speed, assessment of collision risk and positive avoiding action at the centre of the Collision Regulations.

Assess Whether the Bearing Is Changing

A useful practical test is to watch the other vessel against a fixed part of your boat or the distant background.

If the other vessel remains on approximately the same bearing but appears to be getting larger, a collision risk may exist.

A changing bearing does not guarantee safety, particularly at close range or when approaching a large vessel or a tow. If there is doubt, the rules require the navigator to assume that a risk of collision exists.

Take Early and Obvious Action

Avoiding action should be positive, made in ample time and large enough to be readily apparent to the other vessel.

A succession of tiny course changes can create confusion. The other skipper may not know whether we have seen them or whether our movement is simply the result of waves, wind or poor steering.

A clear alteration, made early, communicates intention.

Which Rule Should We Apply?

A common mistake is to begin every situation with the statement:

“Sail gives way to sail according to the tack, and motor gives way to sail.”

That is only part of the story.

Before applying the familiar sailing rules, ask the following questions:

  1. Is either vessel overtaking?

  2. Are we in a narrow channel or fairway?

  3. Is either vessel unable, restricted or severely limited in its ability to manoeuvre?

  4. Are both vessels sailing?

  5. Are both vessels power-driven?

  6. Is one under sail and the other power-driven?

  7. Do local navigation byelaws or directions alter the situation?

The overtaking and narrow-channel rules may apply before the more familiar relationship between a sailing boat and a power-driven vessel.

When Two Sailing Boats Meet

Rule 12 covers two sailing vessels approaching one another when there is a risk of collision.

Boats on Different Tacks

When the boats have the wind on different sides, the boat with the wind on its port side must keep out of the way.

In normal sailing language:

The port-tack boat gives way to the starboard-tack boat.

A boat is normally described as being on starboard tack when the wind is coming over its starboard side. Its boom will usually be carried to port.

A boat on port tack has the wind coming over its port side, with the boom usually carried to starboard.

A useful memory aid is:

Port keeps clear.

Boats on the Same Tack

When both boats have the wind on the same side, the windward boat must keep out of the way of the leeward boat.

The windward vessel is the one nearer the direction from which the wind is coming.

The leeward vessel is farther away from the wind.

A useful memory aid is:

Windward gives way to leeward.

This makes practical sense. The windward boat generally has more opportunity to alter course without being forced directly into the leeward boat.

When the Tack Is Uncertain

A vessel on port tack that sees another vessel to windward, but cannot determine the other vessel’s tack with certainty, must keep out of the way.

In other words, uncertainty is not a reason to continue and hope for the best.

It is a reason to create more separation.

These sail-to-sail provisions appear both in the international regulations and in the Environment Agency’s Thames navigation byelaws.

Sailing Boats and Power-Driven Vessels

Under the general responsibilities between vessels, a power-driven vessel underway normally keeps out of the way of a sailing vessel.

This is the origin of the familiar phrase “power gives way to sail”.

However, it is not an unrestricted privilege for the sailing boat.

A sailing vessel must keep out of the way of vessels that are:

  • not under command;

  • restricted in their ability to manoeuvre;

  • engaged in fishing as defined by the regulations.

A small sailing boat must also avoid impeding a vessel that can safely navigate only within a narrow channel or fairway. The overtaking rules apply regardless of whether the overtaking boat is powered or sailing.

A yacht that is being propelled by machinery as well as carrying sail must not behave as though it is operating solely as a sailing vessel. The regulations also require the appropriate cone, with its apex pointing downwards, to be displayed by a vessel proceeding under sail while also being propelled by machinery.

The practical lesson is simple:

Never assume that displaying sails automatically gives a boat priority.

Following and Overtaking

The overtaking rule is one of the clearest and most important regulations.

A vessel overtaking any other vessel must keep out of the way of the vessel being overtaken.

This applies regardless of vessel type.

Therefore:

  • a sailing boat overtaking a motor cruiser must keep clear;

  • a motorboat overtaking a sailing boat must keep clear;

  • a fast sailing dinghy overtaking a slower sailing boat must keep clear;

  • a safety boat overtaking a rowing boat must keep clear.

A vessel is considered to be overtaking when approaching from more than 22.5 degrees abaft the other vessel’s beam. At night, it would be in a position from which it could see the other vessel’s sternlight but neither sidelight.

If there is doubt, the approaching vessel should assume that it is overtaking.

Most importantly, the overtaking vessel remains responsible until it is finally past and clear. A change in the relative angle does not suddenly turn the encounter into an ordinary crossing situation.

A Practical River Example

Imagine that we are sailing a dinghy downriver and gradually catching a motor cruiser.

It may be tempting to think:

“We are under sail, so the cruiser must keep out of our way.”

That would be the wrong starting point.

Because we are overtaking, we must keep clear.

We should choose a side with adequate room, consider our wind and the cruiser’s wash, pass at a safe distance and remain clear before returning to our preferred course.

The slower boat should behave predictably, but responsibility for the overtaking manoeuvre remains with us.

Power-Driven Vessels Crossing

When two power-driven vessels are crossing and there is a risk of collision, the vessel that has the other on its starboard side must keep out of the way.

It should, where circumstances allow, avoid crossing ahead of the other vessel.

A useful memory aid is:

If you see the other vessel on your right, you give way.

The give-way vessel should take early and substantial action. It might alter course to starboard, reduce speed, stop or pass astern, depending on the circumstances.

The stand-on vessel initially maintains its course and speed so that its movements remain predictable.

These crossing and give-way principles are covered by Rules 15 and 16 of the international regulations.

Narrow Channels Change the Situation

Rule 9 applies to narrow channels and fairways.

A vessel proceeding along a narrow channel should keep as near to the outer limit on its starboard side as is safe and practicable.

More importantly for small-boat sailors, a sailing vessel or vessel under 20 metres long must not impede the passage of a vessel that can safely navigate only within the channel.

A vessel should not cross a narrow channel if doing so would impede such a vessel.

This is where “power gives way to sail” can become dangerously misleading.

A yacht may be under sail, but it must not tack repeatedly across the path of a large vessel that is constrained by the available depth, width or bridge opening.

The larger vessel may have:

  • limited room to turn;

  • a significant stopping distance;

  • strong current acting upon it;

  • a deep draught;

  • restricted visibility from the wheelhouse;

  • no safe route outside the marked channel.

The small sailing boat may be much more manoeuvrable, even if altering course is inconvenient.

Applying This on the Upper Thames

The Upper Thames is not an open sea. It is a relatively confined river with bends, bridges, moorings, shallows and boats travelling both upstream and downstream.

The Environment Agency’s Thames byelaws contain several particularly relevant provisions.

Power-driven vessels proceeding up or down the river should, where safe and practicable, keep to the starboard side of the fairway or mid-channel.

A vessel crossing from one side of the river to the other, or entering the fairway from a side channel, must choose an appropriate time and give way to vessels navigating up or down the river.

An overtaking vessel must keep out of the way of the vessel being overtaken.

Actions to avoid collision should be positive, made in ample time and result in the vessels passing at a safe distance.

Tacking Across the River

A sailing dinghy may need to tack frequently while beating against the wind.

On a narrow river, each tack can take the boat from one side of the fairway to the other. The sailor therefore needs to look well beyond the immediate manoeuvre.

Before tacking, ask:

  • Is a cruiser approaching from upstream?

  • Is a rowing boat hidden behind the sail?

  • Will the tack place us directly in front of another vessel?

  • Is another sailing boat already committed to a manoeuvre?

  • Will we emerge from a wind shadow with enough control?

  • Is there room to complete the tack without being swept towards moored boats?

The rule should not be interpreted as “I am sailing, so everyone else must move”.

A better interpretation is:

“I must sail predictably and avoid obstructing vessels already proceeding along the river.”

What Must the Stand-On Vessel Do?

The term “stand-on vessel” is often misunderstood.

It does not mean a vessel with an absolute right to continue regardless of danger.

The stand-on vessel has three stages of responsibility.

Stage One: Maintain Course and Speed

Initially, the stand-on vessel should maintain its course and speed.

This allows the give-way vessel to predict where it will be and make an effective avoiding manoeuvre.

Unexpected alterations by the stand-on vessel can make the situation worse. The give-way vessel may already be planning to pass astern, only for the stand-on vessel to slow down or turn into the same space.

Stage Two: The Stand-On Vessel May Act

As soon as it becomes apparent that the give-way vessel is not taking appropriate action, the stand-on vessel may take action by its own manoeuvre.

It does not have to wait until collision is inevitable.

This is one of the most important parts of Rule 17. The stand-on vessel is permitted to intervene while there is still room to make an effective and controlled manoeuvre.

Stage Three: The Stand-On Vessel Must Act

When the vessels are so close that avoiding action by the give-way vessel alone can no longer prevent a collision, the stand-on vessel must take whatever action will best help to avoid the collision.

At this stage, standing on is no longer an acceptable option.

In a crossing encounter between power-driven vessels, a stand-on vessel acting independently should, where circumstances allow, avoid altering course to port for a vessel on its own port side. Turning to starboard, slowing or stopping may produce a clearer and safer result, although the skipper must consider the whole situation.

The practical sequence is therefore:

Maintain, monitor, intervene and, if necessary, evade.

Being Stand-On Does Not Remove Responsibility

A stand-on vessel must continue to:

  • maintain a lookout;

  • monitor the other vessel;

  • check whether the avoiding action is effective;

  • consider other surrounding traffic;

  • prepare an escape manoeuvre;

  • avoid creating a second collision while avoiding the first.

It should never continue towards danger merely to demonstrate that the other boat was supposed to move.

There is little satisfaction in being technically correct while repairing a damaged boat—or dealing with something much more serious.

What Should the Give-Way Vessel Do?

The give-way vessel should take early and substantial action to keep well clear.

The best action is normally:

  • early enough to avoid alarm;

  • large enough to be obvious;

  • consistent rather than hesitant;

  • easy for the other vessel to understand;

  • followed through until both vessels are past and clear.

Reducing speed can be extremely effective. Sailors sometimes focus entirely on changing direction, but slowing down may create more time, allow the other vessel to pass ahead and reduce the consequences of any mistake.

On a dinghy, slowing may involve easing the sails, heading slightly into the wind or, where safe, stopping almost completely.

On a powerboat, it may mean reducing throttle, moving into neutral or using astern propulsion when appropriate.

Five Practical Scenarios

1. Two Sailing Boats on Opposite Tacks

Champagne is on port tack and another sailing boat is approaching on starboard tack.

Champagne is the give-way vessel.

The helm should take clear and early action. Depending on the circumstances, this could involve tacking, bearing away or passing astern.

The manoeuvre should not be left until the last few seconds.

2. Two Boats on the Same Tack

Two dinghies are beating upriver on starboard tack. Our boat is to windward.

The windward boat must keep clear of the leeward boat.

We should not squeeze the leeward boat towards the bank, moorings or another obstruction.

3. A Dinghy Catches a Cruiser

Our sailing dinghy is travelling faster than a cruiser and approaches from astern.

We are overtaking.

Despite being under sail, we must keep clear until finally past and clear.

4. A Sailing Boat Tacks Across the Fairway

A cruiser is proceeding steadily upriver while our dinghy is preparing to tack across its route.

The sensible action is to time the tack so that we do not obstruct the cruiser. We might complete the tack earlier, continue briefly on the existing course, slow down or pass safely astern.

The narrow river and local fairway rules matter more than trying to insist upon a simplistic “sail over power” rule.

5. The Give-Way Vessel Does Nothing

We are the stand-on vessel and initially hold our course and speed. The bearing remains steady and the other vessel is getting closer.

We continue monitoring.

When it becomes apparent that the give-way vessel is not acting appropriately, we make an early, clear avoidance manoeuvre while sufficient space remains.

We do not wait until there is only one desperate option left.

Common Misunderstandings

“Sailing Boats Always Have Priority”

They do not.

Overtaking, narrow-channel rules, restricted vessels and local navigation byelaws can all change the relationship.

“The Stand-On Vessel Must Never Alter Course”

Initially, it should maintain course and speed.

However, it may act when the give-way vessel is failing to respond, and it must act when collision can no longer be avoided by the give-way vessel alone.

“A Small Change Is Enough”

Small, repeated changes can be difficult for another skipper to detect.

Avoiding action should normally be positive and readily apparent.

“The Other Skipper Has Seen Me”

Never assume this.

You may be hidden by their cabin structure, sails, passengers, equipment or another vessel. They may also have misunderstood your intentions.

“We Are Racing, So Other Boats Must Keep Clear”

A racecourse does not create a protective bubble around the competitors.

Racing sailors must continue to observe navigation requirements, local directions and the presence of non-racing traffic.

A Simple Collision-Avoidance Routine

A practical routine for a dinghy, yacht or powerboat is:

Look

Maintain a proper lookout in every direction.

Classify

Decide whether the situation involves overtaking, crossing, meeting head-on, sail against sail, sail against power or a narrow channel.

Assess

Ask whether the bearing is steady and the distance is decreasing.

Decide

Identify which vessel should keep clear—but never stop considering what you will do if the other skipper makes a mistake.

Act

Make any avoiding action early, positive and obvious.

Check

Continue monitoring until the other vessel is finally past and clear.

The Deeper Lesson: Predictability Prevents Collisions

The IRPCS are not intended to encourage arguments about priority.

They are designed to make boats behave predictably.

The give-way vessel acts early and clearly.

The stand-on vessel initially maintains a predictable course and speed.

Both vessels keep a lookout.

Both monitor whether the action is working.

Both remain responsible for avoiding collision.

As I have gained more experience on the water, I have realised that knowing the basic rules is only the beginning. Applying them requires judgement.

On the Upper Thames, the wind may change abruptly. A boat may emerge from behind an island or around a bend. A dinghy may lose speed in a wind shadow. A cruiser may be committed to a bridge arch. A boat that appeared well clear may suddenly become a risk after one unexpected tack.

Good seamanship is therefore not simply knowing who should give way.

It is recognising risk early, making intentions clear and always keeping a safe alternative available.

Conclusion: Never Use the Rules to Sail Into Danger

The most important lesson from the IRPCS is not that one boat is “right” and another is “wrong”.

It is that every skipper has responsibilities.

A give-way vessel must take early and substantial action.

A stand-on vessel must remain predictable, but it must also remain alert and be prepared to intervene.

An overtaking vessel keeps clear, regardless of whether it is powered or sailing.

A small sailing boat must not obstruct a vessel that can safely navigate only within a narrow channel.

Local river byelaws and navigation directions must always be considered alongside the international principles.

Knowing these rules should make us more confident, but never overconfident.

The safest sailor is not the one who insists most strongly upon being stand-on.

It is the one who sees the developing situation early enough that no emergency manoeuvre is ever required.

This article is an educational overview rather than a replacement for the official Collision Regulations, local navigation byelaws, current navigation notices or recognised practical training.

Friday, 7 August 2026

Hidden in Plain Sight: The Survey Mark Beneath the Mast at Upper Thames Sailing Club

 



Hidden in Plain Sight: The Survey Mark Beneath the Mast at Upper Thames Sailing Club

There are times when an interesting discovery is not found out on the river, aboard a boat or inside the workshop. Sometimes it is quite literally beneath our feet.

At Upper Thames Sailing Club, at the base of the mast on the lawn, there is a small circular hole accompanied by a black, three-part arrow. It would be easy to walk past it without giving it a second thought. Once noticed, however, it immediately raises questions.

Is it a trig point? Why was it placed there? What was it used to measure? And why has such a small mark survived when the methods of surveying Britain have changed so dramatically?

The answer takes us into the history of mapping, engineering and the remarkably precise measurements that underpin the modern world.

First, Is It Actually a Trig Point?

The mark is likely to be described casually as a trig point, but the photographs suggest that it is more precisely a survey benchmark, possibly a rivet or pivot-style benchmark.

The distinction matters.

A traditional trig point, or triangulation point, records a precisely established horizontal position. In Britain, the most recognisable examples are the concrete triangulation pillars found on hills and other prominent locations.

A benchmark, by contrast, records a precisely measured height.

Ordnance Survey explains the difference simply: trig pillars established accurate eastings and northings, while benchmarks established height above Ordnance Datum. Many trig pillars also carried a separate height mark, which is one reason the two terms are often confused.

The small circular feature and arrow at Upper Thames appear more like a horizontal benchmark than a conventional trig pillar. Confirming its exact type and original recorded height would require locating it in the Ordnance Survey benchmark archive or an earlier surveying record.

Nevertheless, it is certainly part of the same fascinating family of fixed survey markers.

What Does the Arrow Mean?

The three black shapes form a stylised broad arrow pointing towards the circular reference point.

Traditional benchmarks were often cut into walls, bridges, churches, milestones and other durable structures. On vertical surfaces, an arrow normally pointed towards a horizontal line. That line provided a repeatable position for a levelling staff.

On a horizontal surface, the precise reference could instead be a metal rivet, bolt or small depression. Specialist descriptions of these markers explain that some depressions were designed to accept a standard-sized steel ball, creating a repeatable point from which a measurement could be taken.

In the photograph, the arrow directs attention to the small circular point above it. The hole may be the original pivot, or it may once have contained a rivet that has since disappeared. That cannot be confirmed from the image alone.

The arrow is therefore not merely decorative. It tells the surveyor, “This is the point that matters.”

What Is a Trig Point?

“Trig” is short for trigonometrical station.

During the retriangulation of Great Britain, surveyors established a network of accurately positioned points across the country. Between 1936 and 1962, around 6,500 familiar concrete trig pillars were constructed. Each pillar provided a stable platform for a theodolite, an instrument used to measure horizontal and vertical angles.

Surveyors began with a very accurately measured baseline. They then observed other distant points and measured the angles between them.

If one side of a triangle and its angles are known, the remaining sides and positions can be calculated. The surveyors could then move to the next point and build another triangle.

Repeated across the country, those triangles created a connected national framework.

This was not simply a collection of isolated pillars. It was an enormous mathematical network supporting accurate map-making.

Why Were Trig Points Needed?

Imagine attempting to create a detailed map before satellite navigation existed.

A surveyor needed to know exactly where every town, road, railway, river, hill and significant building belonged. Local measurements were useful, but all those individual surveys had to fit together consistently.

Trig points gave surveyors reliable control positions from which other features could be measured.

They helped establish:

  • national map coordinates;
  • the locations of settlements and landmarks;
  • the shapes and positions of roads and railways;
  • boundaries and major structures;
  • the positions of coastlines, rivers and hills;
  • a consistent framework connecting local surveys.

A survey carried out in Buckinghamshire had to agree with one conducted in Oxfordshire, Berkshire or Cornwall. The triangulation network made that possible.

What Is a Benchmark?

A benchmark answers a different question.

A trig point helps establish:

Where is this point?

A benchmark helps establish:

How high is this point?

Ordnance Survey benchmarks record heights in relation to Ordnance Datum Newlyn, the national height reference for mainland Great Britain. That datum originated from measurements of mean sea level recorded at Newlyn in Cornwall over a six-year period.

Once the height of one benchmark had been established, surveyors could transfer that height to another location using precision levelling.

A simplified levelling calculation is:

Height of new point = height of known point + backsight reading - foresight reading

The measurements could be repeated from benchmark to benchmark, gradually extending a network of known heights across the country.

Why Is It Called a Benchmark?

The name has a very practical origin.

Traditional marks included a small horizontal cut. A levelling staff or supporting fitting could be positioned against that line, forming a stable and repeatable “bench”.

That physical bench gave us the word benchmark.

The term is now used much more broadly. Businesses compare performance against benchmarks, computers are benchmarked for speed, and schools may use benchmark assessments. In each case, the basic idea remains the same: there is a fixed reference against which something else can be measured.

Ordnance Survey records show that more than 500,000 benchmarks were created across Great Britain. Many have disappeared as buildings have been demolished, roads widened and structures replaced.

Why Put One at the Bottom of a Mast?

A benchmark needs a firm, durable and recognisable location.

The concrete foundation beneath a mast offers several advantages:

  • it is unlikely to move during normal use;
  • it provides a solid horizontal surface;
  • it is easy to describe in survey records;
  • it is reasonably accessible;
  • it is less likely to be disturbed than a mark placed in soil;
  • the tall mast makes the general location easy to identify.

The mark may predate the present mast, may have been incorporated when the base was constructed, or may have been installed because the mast foundation provided a particularly suitable permanent structure.

Without finding its original survey entry, it is impossible to say precisely when or why this individual mark was created. Its position, however, makes good surveying sense.

Why Accurate Height Matters Beside a River

Finding a height benchmark at a sailing club beside the Thames is particularly appropriate.

Precise height information can support work involving:

  • river and flood levels;
  • bank and pontoon construction;
  • drainage gradients;
  • building foundations;
  • road and path levels;
  • bridge clearances;
  • utility installation;
  • environmental monitoring;
  • land and topographical surveys.

A difference of only a few centimetres may matter when water levels rise, when a drain must flow correctly or when a new structure must connect with an existing one.

Today, accurate height data also contributes to flood modelling, infrastructure projects, communications systems, renewable-energy planning and three-dimensional mapping.

This small mark may look unimportant, but it belongs to a system that helped engineers and map-makers describe the land in three dimensions.

How Would Surveyors Have Used It?

A survey team using the benchmark would place a levelling instrument on a stable tripod at a suitable nearby position.

A graduated levelling staff would be placed on the benchmark’s exact reference point. The surveyor would take a reading through the instrument.

The staff would then be moved to another point, where a second reading would be taken. The difference between the readings revealed the difference in height between the two positions.

The process could be repeated along a road, through a town, beside a river or across a construction site.

Accuracy depended upon:

  • keeping the instrument level;
  • placing the staff vertically;
  • using the exact benchmark point;
  • keeping sighting distances sensible;
  • checking readings;
  • repeating or closing the levelling route to detect errors.

It was careful, methodical work. A small mistake at one stage could travel through the rest of the survey.

Are These Marks Still Used?

Most of the historic benchmark network is no longer maintained for modern national surveying. Ordnance Survey warns that old benchmark values may have been affected by movement, redevelopment or subsidence and should not automatically be treated as current precision control.

Modern surveyors generally use Global Navigation Satellite Systems, including GPS, connected to the OS Net network of permanent reference stations. Ordnance Survey says this technology allows new map detail to be positioned to within a few centimetres without relying on the old triangulation pillars.

That does not make the old marks unimportant.

They remain physical evidence of how Britain was mapped before satellite positioning. They connect mathematics, geography, engineering, history and the landscape itself.

A Practical Investigation for Students

This discovery could form the starting point for an excellent geography, mathematics or physics activity.

1. Locate the marker

Photograph the mark from a distance and close up. Record its position relative to permanent features such as the mast, clubhouse and river.

2. Record its characteristics

Measure the diameter of the circular point, the dimensions of the arrow and the size of the concrete base.

Do not damage, deepen, repaint or alter the mark.

3. Find its approximate coordinates

Use a phone or handheld GPS receiver to record an approximate latitude, longitude and OS grid reference.

A phone will not normally provide professional surveying accuracy, but it can provide enough information to search historical records.

4. Search the archive

The Ordnance Survey maintains a searchable archive of historic benchmarks. Searches can be made using a postcode, grid reference or coordinates. The archive is no longer maintained as an active national control network, but its records remain available.

5. Compare measured heights

A simple optical level, laser level or suitable surveying instrument could be used to compare the marker’s height with the clubhouse threshold, riverbank, pontoon or other fixed positions.

This should be treated as a relative educational exercise rather than an attempt to recreate an official datum.

6. Discuss measurement uncertainty

Students could investigate why readings differ and consider errors caused by:

  • an uneven or moving staff;
  • instrument alignment;
  • reading the wrong graduation;
  • long sighting distances;
  • thermal effects;
  • ground movement;
  • using an approximate rather than an official benchmark value.

That turns a small mark in the ground into a lesson about scientific measurement, uncertainty and the importance of repeatable reference points.

The Mathematics Hidden Beneath Our Feet

The mark also demonstrates how abstract mathematics becomes something practical.

Triangulation uses angles and calculated distances to establish horizontal positions. Levelling uses differences in staff readings to establish vertical positions.

Together, these provide three essential pieces of information:

  • east-west position;
  • north-south position;
  • height.

In modern language, we might call these x, y and z coordinates.

Surveying therefore brings together geometry, trigonometry, optics, careful observation, instrument design, data recording and error analysis. The maps we use so casually are the final product of all that work.

A Personal Reflection

I have probably walked past this marker at Upper Thames Sailing Club many times without noticing it.

Attention at a sailing club is normally directed upwards towards the flag, across the river towards the wind or down at the boats and equipment. It took a closer look at the base of the mast to reveal something quite different: a small piece of Britain’s surveying history.

That is one of the pleasures of investigating the familiar. A feature that initially looks like a hole and three patches of black paint opens a path into trigonometry, national mapping, sea-level measurement, flood planning and modern satellite navigation.

It also reminds us that useful discoveries do not always require a journey to an unfamiliar place. Sometimes they require us to look more carefully at places we already know.

Conclusion: A Small Mark with a National Story

The feature beneath the mast at Upper Thames Sailing Club may commonly be called a trig point, but its appearance suggests that it is more likely a rivet or pivot-style benchmark used to identify a precise height reference.

A traditional trig point established horizontal position. A benchmark established height. Both were parts of the surveying systems that allowed Britain to be mapped consistently and accurately.

Modern satellites have largely replaced the daily use of these old markers, but the physical marks remain. They are small monuments to the surveyors who measured the country using theodolites, levelling staffs, mathematics and extraordinary patience.

The next time you see an arrow cut or painted onto a wall, bridge, stone or concrete base, stop and look more closely.

You may be standing beside a surviving reference point from the system that helped map modern Britain.