More than 200 years ago, two Royal Navy lieutenants travelled to Bermuda to embark on a ground-breaking project to map the island’s landscape, seabed and perilous reefs.

The culmination of eight years’ meticulous work by Thomas Hurd and Andrew Evans was arguably the most important survey ever conducted in Bermuda.

This evening, descendants of the two surveyors from Australia, Canada and Bermuda will gather at the National Gallery for the launch of a new book that tells the untold story behind one of the island’s most significant pieces of maritime heritage.

The book’s author, Adrian Webb, has spent the past 17 years researching Hurd and Evans’s epic mission to chart and measure the island’s reefs and seabeds; measurements that to this day remain the foundation of modern sea charts of Bermuda.

Dr Webb, who heads up the UK’s Hydrographic Office Archive in Somerset, trawled through thousands of communications and records in both Bermuda and the National Archives in London to produce Thomas Hurd & His Hydrographic Survey of Bermuda, 1789-97.

“I first saw the map in its original form at work 17 years ago when I was following up a research query,” Dr Webb said. “I was immediately impressed by its incredible detail but also its size. It covered two pieces of 6ft square paper.”

“It had a wow factor that made me want to find out more about the story and the people behind the survey.”

The original Hurd survey had been kept in the Hydrographic Office archives for more than 200 years before it was moved to the National Archives in London last year.

Dr Webb’s research revealed that both Lieutenant Hurd and Lieutenant Evans travelled to Bermuda in 1789, after the end of the American War of Independence, to survey the island and see if it was a suitable venue for a naval port.

The pair, led by Lieutenant Hurd, measured the sea depths at thousands of locations using a plumb line to map the seabed. They also meticulously recorded the position of the edges of the reefs.

During the project Lieutenant Hurd lived in the Stiles building off St George’s Town Square with his wife. The couple’s son, Samuel Proudfoot Hurd, was born in Bermuda and served at the Battle of Waterloo.

“This survey was a labour of love for Hurd,” Dr Webb said. “He also discovered during this process that the longitude that St George’s had previously been measured on was wrong.

“Hurd was the first person to establish the correct position of Bermuda with great accuracy using the stars and the planets and worked with pilots Jemmy Darrell and Jacob Pitcarn to complete the survey.

“Hurd and Evans also identified the site of a naval facility at Grassy Bay. This, it can be argued, changed the future of Bermuda forever, as it resulted in the militarisation of the island.”

After leaving Bermuda in 1797, Lieutenant Hurd, who had already been promoted to commander, was made hydrographer for the Admiral Board and served in this top role until he died in England in 1823.

Dr Webb, 48, added: “There was an awful lot of correspondence in the archives from Hurd as well as log books, reports and newspaper cuttings to go through, although his personal journal from Bermuda has never come to light.

“It took a long time to get everything together; it has been an amazingly rewarding journey. I hope people in Bermuda find the book interesting. This survey is a really important piece of the island’s maritime history and it is still very relevant to this day.

“Lots of people have helped me along the way, but the National Museum and Edward Harris have really been at the front of bringing this project to fruition.”

Dr Harris told The Royal Gazette that Hurd’s “magnum opus” of the lands and reefs of Bermuda was “without parallel in our history”.

He added: “While historians and many other locals have known that Hurd made the survey it seems that no one from the island ever saw the original and thus its significance was overlooked.

“Aside from the depiction of the reefs, which is staggering in its detail considering the difficulty of surveying objects under the water from a boat, the information that has been recorded on the land is a feast for historical interpretation about the nature of Bermuda towards the end of its second century of settlement.”

Dr Harris also thanked the new book’s sponsors, Jennifer Darrell, Toni Moutray and Deborah Darrell Mackenzie. The three sisters are the children of the late Bert and Joan Darrell.