HYDROGRAPHIC

A clear focus

Producing digital charts for the UK Hydrographic Office and delivering practical sessions and lectures to MSc students – the PLA’s hydrographic team is way ahead of the field.

 An underwater sonar scan  of the Thames Barrier. An underwater sonar scan of the Thames Barrier.

Ever tried producing an accurate and precise picture of something you can’t actually see? It’s not impossible, but it does require skill, patience, the latest technology and a meticulous attention to detail. Who has all of those? It’s time to introduce PLA’s hydrographic team!

These are the people who are responsible for surveying the 400 square miles of the tidal Thames and estuary, a task that ensures vessels can make their way to and from their berths with the confidence that they won’t encounter a shifted sandbank, a build-up of sediment or unexpected obstructions.

The PLA has the busiest hydrographic department in the UK – employing a total of 17 people including eight qualified surveyors, operating three dedicated survey craft, and with access to a huge range of high-tech equipment.

“We have responsibility for safety of navigation in the River Thames; our job is to measure the depths, process the information, review the data and notify the harbourmaster and others of anything navigationally significant,” says port hydrographer John Dillon-Leetch.

All of this information feeds into the drawing up of paper and digital navigation charts. Until very recently, the PLA sent its survey data to the UK Hydrographic Office (UKHO), which would then produce the charts. But since the end of 2017, the hydrographic team has been authorised to produce digital charts in-house for sending to the UKHO for direct incorporation into the UK national charting portfolio.

“We are now delivering fully compliant electronic navigational charts to the mariners via the UKHO,” says John Dillon-Leetch.

Unsurprisingly, the shipping industry is moving towards using only digital charts – indeed, in 2018, demand for the PLA’s digital products was ahead of paper for the first time. For those mourning the demise of a romantic, old-fashioned paper chart, he points out: “It is just as important to think about the look of a digital chart as a paper chart, and also gives the user more control over the level of data and detail they wish to see, whereas on a paper chart the displayed/charted data is pre-determined.”

The steady migration away from paper also means that information and digital charts can be much more swiftly updated, he adds. “Some customers still must legally carry paper charts aboard or prefer to have the paper product, and we will supply that need/requirement going forward, but the flexibility you can have with the digital product is really important. Our pilots carry tablet computers on which they can see real-time tides and updated electronic charts which are as real-time as we can get. From the shore, you can ‘digitally’ board a ship with real-time information, and see what is happening onboard and what any other vessels nearby are doing. This is all part of the fourth revolution of data and robotics.”

The statutory duty of the hydrographic team never stops. As a conservancy authority, the PLA is responsible for a 95-mile stretch of the River Thames and that means water depths, tidal heights and tidal flows must all be accurately measured and predicted.

The entire river, bank to bank, is surveyed on a rolling programme over five to 15 years, depending on the characteristics of a particular area. About 90 navigational areas which are subject to greater change are surveyed more often, up to once a month in some cases. The team also provides the ‘eyes’ for PLA divers entering the water for tasks such as clearing obstructions or checking the condition of structures.

The team has access to a massive ‘tool box’ to provide geophysical, geotechnical and high-resolution multibeam echo sounder (MBES) surveying, side-scan sonar and LIDAR surveying, 3DChirp imaging, high-resolution photography, and underwater photography and video. Gradiometer technology picks up magnetic fluctuations which help detect metal objects on or in the river bed. Drones and ASVs (autonomous surface vessels) are used too.

Since the start of 2018, the PLA has been running ultra-high resolution seismic (UHRS) surveys in central London. This provides detail of what is going on below the river bed, with capability to ‘see’ the ground structure down to 100 metres, allowing analysis of different geological layers below the river bed. This can provide valuable information to support the feasibility study or design of marine structures, river crossings or other new infrastructure projects.

It isn’t just depth of experience – it’s length of experience too. The department has an archive of more than 100 years of surveys which can prove invaluable in forecasting and modelling the impact of developments. “Over the past year, the team has undertaken a campaign of scanning and digitalisation of a major part of the paper chart archive so we have it easily accessible for future reference.”

Tide and time

The PLA’s tidal application, accessible via its website or mobile devices, enables anyone, from the general public to shipping masters, to view real-time tidal data and make plans accordingly.

This is complemented by a sophisticated passage planning software used by the VTS centres, to identify tidal windows and under keel clearances to ensure vessels have a safe passage.

Farewell to John Pinder

John Pinder retired at the end of 2018 after serving 18 years as port hydrographer and a total of 30 years with the PLA.

Recognised as one of the foremost surveyors and port hydrographers in the world, he joined the PLA as a surveyor. Having been appointed port hydrographer in 2000, he led the PLA on its journey from a position of paper charts only, and still using lead lines in some instances, to today’s high-tech, data-intensive operation.

Passing on the skills

The PLA’s hydrographic practitioners have played a central role in the delivery of University College London’s MSc in hydrography since 1996. All its surveyors are involved, delivering practical sessions, lecturing and supporting students with their dissertations – reflecting the high standing which the team has in the industry

  Geo-referenced photography for asset inspection at Canary Wharf.. Geo-referenced photography for asset inspection at Canary Wharf.

In 2018, the hydrographic department was re-accredited to deliver the International Hydrographic Organisation’s category A course.

“The course involves a substantial practical element, and we provide the facilities and support for students to apply what they have learned,” says John Dillon-Leetch. “We have graduates working all over the world from this course – and one of them is in our team.”

The team’s links with institutes and equipment suppliers are vital, supporting the development of new tools. Equipment manufacturers’ new products and systems are often tested out by the PLA.