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Mark Milburn’s Cornish Wreck Ramblings, Part 1: Accuracy, inaccuracy and alternative co-ordinates



We are in a marvellous age of technology, where we can pinpoint a needle in a haystack within inches. In the days before GPS and even Decca, there were transits. Transits can be good or bad; a good transit can be as accurate as any GPS. A bad transit is just bad.

I once went looking for a plane wreck. It hadn’t been dived for a long time, and we wanted to see what was left. It was a forty five minute boat ride but the transits were supposed to be good. We had to line up a telegraph pole with the third tree, out of four, in the hedge behind.

Something had happened to one of the trees; there were now only three, all spaced out a little… so which one was the original third tree? We used the sounder to look but found nothing, so we guessed at one of the trees…. and found sand. So a good transit had gone bad!

Decca was an improvement over transits when you were further offshore. Towards the end of its life, the last version of Decca was quite good, but eventually GPS took over. GPS was a little all over the place to start with, so along came Differential GPS (DGPS), which used a known fixed local transmitter to correct any errors. These errors were deliberate errors used by the Americans, so the rest of the world would be at a disadvantage. Once the Americans no longer added their “fudge factor”, the D was no longer needed.

So, what could possibly go wrong now? A few years ago, there was a news item on the BBC about a wreck called the Antoinette. It had become exposed as the sand shifted in the Camel Estuary. The report stated it was on the Doom Bar; it also stated that the bomb squad had been tasked with removing the remains of the wreck as they were a hazard to shipping. I headed over with my camera, but found nothing, just sand. I then headed back to Padstow to say ‘Hi’ to the staff at the lobster hatchery. While there, I could see something going on in the middle of the river. I was told it was the bomb squad about to blow a wreck up. But that was Town Bar not the Doom Bar – they are over a mile apart. Not the most accurate of reporting! That was quite recent though; when looking for old wrecks, with old information, the difference could be a lot worse.

Surely though, modern GPS is infallible? It is very good, as long as the numbers are accurate. They could be written down wrong, accidentally or deliberately. They could be from an alternative dataset. Most people use WGS 84, World Geodetic System, which originated in 1984. Some people don’t.

Myself and some friends wanted to dive the wreck of the St George, which lays twenty miles off shore in a depth of sixty five metres, and we wanted an accurate position. We asked around, got some accurate marks, and headed out. Once in the area, we watched the sounder as we went over the co-ordinates, but all we found was a flat sea bed. We repeated this several times, but still nothing. Time was running out to dive at slack water, but the sea bed was completely flat all around us.

Then one of us remembered that the person who gave us the co-ordinates liked to use OSGB 36, a different dataset. We quickly changed the GPS to OSGB and headed off. We arrived at the new location, and lo and behold, there was the wreck. So the co-ordinates were right… just an alternative right.

So, every form of position fixing has potential errors. Sometimes, there is nothing you can do about it… except guess!

Find out more about Mark and Atlantic Scuba at

Mark Milburn is the owner of Atlantic Scuba in Falmouth, Cornwall, England, and is an SDI/TDI/NAS/RYA Instructor and a Commercial Boat Skipper. Although often referred to as a maritime archaeologist, he prefers to call himself a wreck hunter. Find out more about Mark and Atlantic Scuba by visiting

Marine Life & Conservation

Dive Guides invited to apply for the Green Fins Dive Guide Scholarship



Reef-World’s campaign is helping dive guides in need receive Green Fins environmental certification

The Reef-World Foundation – international coordinator of the UN Environment Programme’s Green Fins initiative – is calling for dive guides to submit their application for the Green Fins Dive Guide Scholarship.

As a result of the Scholarship campaign, dive guides working around the world – including Brazil, the Philippines, Egypt, Colombia, South Africa, Indonesia and Turkey – have received their certificate proving their status as a Green Fins certified dive guide. Yet, thanks to funding from Reef-World’s partner Paralenz, 149 more scuba diving guides will be able to receive their Green Fins Dive Guide e-Course environmental certification.

Dive guides who meet the criteria (outlined below) can apply for the scholarship at any time through the Green Fins website. To be eligible for the scholarship, guides must:

  • have completed and passed all modules of the Green Fins Dive Guide e-Course
  • be able to demonstrate they or their employer are not financially able to purchase the certificate
  • be a national of a country which receives official development assistance from the Development Assistance Committee (DAC) of the Organisation for Economic Co-operation and Development (OECD).

The Scholarship was created in response to feedback from dive guides who had passed the Green Fins Dive Guide e-Course and were keen to download and display their personalised electronic certificate but were not financially able to cover the associated cost (£19 / $25 USD). The personalised electronic certificate can be displayed to entice eco-minded guests by informing them the guide has received this vital environmental certification and is aware of how to reduce the negative environmental impacts associated with diving.

Diving related damage to sensitive marine ecosystems, including coral reefs, is becoming an increasingly significant issue. This damage makes them less likely to survive other local and wider stressors, such as overfishing or run-off from land containing pollutants and plastic debris as well as the effects of climate change, such as rising sea temperatures. The Green Fins Dive Guide e-Course, created with the support of Professional SCUBA Schools International (PSS) and running on their innovative EVO e-learning platform, teaches dive professionals how to prevent diving-related damage to coral reefs by following the highest environmental standards and better managing their guests to prevent damage to the reef.

Sam Craven, Programmes Manager at The Reef-World Foundation, said: “We’re proud to be offering dive guides around the world the opportunity to become Green Fins certified; no matter their background. Both the e-Course and the Scholarship have been a great success so far and we’re delighted to see so many dive professionals demonstrating their commitment to sustainable tourism by taking the course. We urge dive guides who haven’t yet taken the course to consider taking this step and welcome Scholarship applications from anyone who meets the criteria. Together, we can protect coral reefs through sustainable diving and we’d love as many dive guides as possible to join us.”

Dive guides who want to be considered for scholarship can visit to apply.

To donate to the Green Fins Dive Guide Scholarship Fund, please visit

Supporters who are interested in helping additional dive guides receive their certifications can also donate to Sponsor a Dive Guide.

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Marine Life & Conservation

Go Fish Free this February



There are no longer plenty more fish in the sea! Fish Free February challenges you to help protect our oceans by removing seafood from your diet for 28 days and helping to raise awareness of the issues caused by intensive fishing practices.

Our oceans are in a state of global crisis, brought about by ocean warming, acidification, pollution, and habitat destruction. However, the biggest immediate threat to ocean life is from fisheries. Each year an estimated 1-2.7 trillion fish are caught for human consumption, though this figure does not include illegal fisheries, discarded fish, fish caught to be used as bait, or fish killed by not caught, so the real number is far higher. It is no wonder then, that today nearly 90% of the world’s marine stocks are fully exploited, overexploited or depleted. If we do not act fast, overfishing and damaging fishing practices will soon destroy the ocean ecosystems which produce 80% of the oxygen in our atmosphere and provide three billion people with their primary source of protein.

Fish Free February, a UK-registered charity, is challenging people around the world to take action for marine life in a simple but effective way. Take the Fish Free February Pledge and drop seafood from your diet for one month, or beyond. Fish Free February wants to get people talking about the wide range of issues associated with industrial fishing practices and putting the well-being of our oceans at the forefront of dietary decision-making. A third of all wild-caught fish are used to create feed for livestock, so Fish Free February urges us to opt for plant-based dishes as a sustainable alternative to seafood, sharing our best fish-free recipes on social media with #FishFreeFebruary and nominating our friends to do the same.

“Not all fishing practices are bad” explains Simon Hilbourne, founder of Fish Free February. “Well-managed, small-scale fisheries that use selective fishing gears can be sustainable. However, most of the seafood in our diet comes from industrial fisheries which often prioritise profit over the well-being of our planet, resulting in multiple environmental challenges. In some cases, the fishing industry has even been linked to serious human rights issues such as forced labour and human trafficking! Fish Free February hopes to shed more light on fishing practices, create wider discussion around these issues, and offer solutions to benefit people, wildlife, and the natural environment.”

To learn more about these issues and to take the Fish Free February pledge visit

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E-Newsletter Sign up!


This is the perfect start to your 2021 diving season… and at an incredible lead-in price of just £885 per person.

Jump on board the latest addition to the Emperor fleet and enjoy diving the famous sites of the Red Sea with this fantastic special offer. This itinerary takes in the wonderful South & St Johns from 26 February – 05 March 2021.  

Subject to availability – limited flight seats at this price so don't delay!

Call Diverse Travel on 01473 852002 or email to book your spot!

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