The Diamond Head Lighthouse that stands today has been a lifesaving navigational beacon for the past 100 years, preventing vessels from running aground on the jagged reef over which it presides.

Even now, as captains use GPS technology to plot their courses, the lighthouse remains the reliable method for preventing groundings.

On a dark night under heavy clouds, the lighthouse is the navigational alternative to modern-day instruments, providing a beacon for mariners to help indicate where the reef begins.

“It’s a backup,” said Dan Ford, an official with the just completed Transpacific Yacht Race, a 2,225-mile journey from Los Angeles to Honolulu. “If power goes out, which these things do happen, you need to rely on the old system.”

Ford said it’s also vital to Transpac officials as a communications center in concert with the Diamond Head buoy as a sighting device to determine finish times for scores of participating yachts in the biennial race.

The original tower that housed the Diamond Head beacon didn’t last 20 years before it was replaced in 1917 by one that was raised from 40 feet to the current 55 feet. When it was first completed, its internal staircase was one of its notable features.

Today, in addition to its role in preventing groundings, the lighthouse, operated by the U.S. Coast Guard, is seen as an asset in reducing the chances of environmental mishaps, including from oil spills.

“We’re preventing things from spilling into the water … so it is very vital to the Hawaiian Islands,” said Coast Guard spokeswoman Petty Officer 3rd Class Amanda Levasseur.

While the lighthouse is still being used to protect life and the environment, in the late 1800s at least a couple of vessels weren’t as lucky.

In 1893, the SS Miowera struck the Diamond Head reef after the captain mistook the position of Diamond Head Crater. The steamship China ran aground on Diamond Head reef four years later, prompting the building of the original structure, according to the Hawaii Historical Society.

In 1921 a lightkeeper’s home was built nearby, and that now serves as home for commanders of the Fourteenth Coast Guard District.

Modernization has allowed for the lighthouse to be fully automated and have LED lighting with 60,000 candlepower visible up to 18 miles out to sea, the Coast Guard said.

Kraig Anderson, the creator of the website lighthousefriends.com, said on a clear day, those in the lighthouse can see east and west Oahu. “It’s a great panoramic view. It’s fantastic,” Anderson said.

The Diamond Head Lighthouse was put on the National Register of Historic Places in 1980.

The Coast Guard will commemorate the centennial with three public open houses sometime in late August, and plans an announcement when dates are set.