HYDROGRAPHIC

Depth of knowledge

The expertise of the hydrographic team has led to the UKHO decision to incorporate the PLA’s electronic charts directly without redrawing.

PLA Hydrographic VesselHydro flagship – survey vessel Maplin alongside

The expertise of the Port of London Authority’s hydrographic team reaches amazing depths – and heights. And that expertise is critical to shipping. How else would vessels have the confidence to make their way to and from their berths in the River Thames without worrying that they might hit unexpected obstructions, shifting sandbanks, a build-up of sediment or even a piece of unexploded ordnance on the river bed?

The PLA’s hydrographic team has long been recognised as being ahead of the field – and during 2017, a very important announcement served to confirm that status.

For decades, the PLA has sent its survey data to the UK Hydrographic Office, which would use this to produce its own paper charts and, more latterly, digital charts. However, from the end of 2017, the hydrographic team will send the ‘finished product’ – electronic navigation charts which will be directly incorporated into the UK national charting portfolio.

“Our safety of navigation surveys are now being accepted by the UKHO. So ships coming upriver will have PLAgenerated charts on their electronic chart screens,” says port hydrographer John Pinder. “We are proud to be the first port in the UK to have our charts used without being redrawn by the UKHO. To meet this accreditation, we proved that we have a resilient and robust system in place, which links into our quality management system. We are one of the first in the world to achieve this and it is a major step forward.

This is down to the expertise and capability in our team – digital electronic chart processors are difficult to find.”

The PLA has invested in ESRI (Environmental Spatial Research Institute) software and the hydrographic department is working to make its data available throughout the organisation digitally. “We are moving away from paper charts, which will be phased out gradually.”

All of the PLA’s electronic charts will be available to stakeholders, international shipping and pilots. As every PLA pilot now carries a tablet IT device, the timing of this advance in electronic charting ties in perfectly.

“We are very much going down the digital route,” says John Pinder. “We have been using sophisticated digital techniques for gathering data for the past 20 years – and now we are moving to make it available to everyone.”

As a conservancy authority, the PLA is responsible for a 95-mile stretch of the River Thames. Across a 400 square mile area of river and seabed, water depths, tidal heights and tidal flows must all be accurately measured and predicted. To meet that requirement, the hydrographic team surveys the entire river, bank to bank, on a rolling programme over five to 15 years, depending on the characteristics of a particular area. In short, the work never, ever stops.

There are about 90 navigationally significant areas which are subject to greater change and these are surveyed more frequently – once a month in some cases.

New vessels

Two years ago, the PLA took delivery of the 17-metre Maplin, a purpose-built new hydrographic survey vessel. Since then, the catamaran has certainly earned its keep – being busy with safety of navigation surveys and also seismic survey work such as 3D Chirp imaging and analysis.

In 2018, the Maplin will be joined by another new arrival. The 14-metre Thame, a former wind farm supply and crew transport boat, has been converted into a hydrographic survey boat to meet the PLA’s specific needs and will be operational early in 2018.

“Thame is only five years old and in excellent condition; converting this highquality boat is much faster than building from scratch, which typically involves a 15-month lead-in period, as well as engineering time,” says John Pinder. “There are considerable savings in both costs and time, and it’s also environmentally friendly to be upcycling a boat.”

Thame will replace the survey boat Yantlet, which will be retired after more than two decades of service. LiDAR (laser) surveying equipment installed on Yantlet will be moved across to Thame. The Maplin has similar LiDAR kit onboard.

Seeing the unseen

The quality of the PLA’s hydrographic team’s surveying and analytical work is crucial for the confidence and safety of all river users. In short, they provide the ‘eyes’ that can see through the murky depths to the river bed, to confirm water depths and identify where storms, shifting sand banks and tidal flows may have reduced those depths at critical points in the river.

Such is the pinpoint accuracy of the survey equipment, the team can detect items as small as 12 centimetres in size, and identify whether it’s a piece of iron or wood, or even a tyre. As a result, they can be very specific in their instructions to divers for the item’s safe inspection and removal.

PLA ASCThames innovators – an autonomous survey vessel is the latest kit trialled by the hydro team

High-resolution multibeam echo sounder (MBES) technology enables the surveyors to detect and monitor even small changes, and alert mariners immediately. Side-scan sonar and LIDAR surveying, GeoChirp 3D and high resolution photography are also used and the team continues to examine, adopt and develop new survey techniques.

In recent months, trials have been carried out using drones for difficult-to access areas. “We are also looking seriously at robotic surveys for sandbanks and danger areas which can’t be easily accessed by normal manned boats,” says John Pinder. “Maplin was designed to carry an ASV (autonomous surface vessel) on board, and we are continually looking at more efficient ways of collecting data.”

And this isn’t only about below water – the range of technology enables the team to survey structures above water too, so that the condition of bridges, jetties and other infrastructure can be inspected for damage or wear.

Commercial support work

As well as serving the needs of the PLA as the statutory harbour and conservancy authority, the hydrographic department works closely with port and terminal operators on a commercial basis, carrying out surveys, sampling and monitoring sediment quality, and providing data to support them in their operations and developments.

The work carried out in support of the Tideway project has been huge, and now the team will also be providing support services as plans for the new Thames Crossing move forward.

In addition, the department has carried out a large amount of work in support of Forth Ports’ expansion at the Port of Tilbury – so-called Tilbury2 – which takes in a large amount of the former power station land and river frontage.

PLA Hydrographic Sonar and Laser imageBarnes Railway Bridge area surveyed by vessel based Sonar and Laser.

East Mouse Channel

The charmingly named East Mouse Channel is now open for business. Ongoing conservancy work by the hydrographic team shows which sections of the river are naturally getting deeper or shallower, and survey work has demonstrated that the East Mouse Channel is deep enough to provide an alternative route into the Thames for smaller vessels.

“We have opened up East Mouse Channel from Barrow Deep, providing a channel seven metres deep which requires no dredging regime,” says John Pinder.

Tidal monitoring

The hydrographic department monitors and controls 16 tide gauges strategically located along the Thames – and this is particularly important for larger, deeper ships that are reliant on short tidal windows for access.

The PLA’s daily tide predictions stretch ahead five years, enabling ship operators to plan schedules according to the water depth available. The team produces a Tidal Booklet entirely from in-house information and software.

The Thames has an incredibly fast tidal flow and this is also carefully measured and predicted; understanding how fast the tide flows is also extremely important for safe navigation