PORT TOWNSEND — Imagine a flashlight — a really big, bright one — shining upon the deteriorated hulk of a sunken passenger liner on the floor of Admiralty Inlet.

The light would cast shadows in the dark water beyond the remains of the ship.

That’s what occurs when a sonar scan is made of an object.

The resulting images have to be manipulated to remove the ghost shadows to get an accurate “picture” of the target — in

this case, the wreck of the

SS Governor, which sank in 240 feet of water around midnight April 1, 1921.

The Everett-based OceanGate company spent four days last week taking sonar and video images of the doomed liner from the comfort of its five-person Antipodes submarine.

“You visually have to piece together the scans in order to see the depth of the shape,” said Joel Perry, vice president of expeditions for OceanGate.

“Things in profile look much different than in three-dimensional scans.”

OceanGate’s expedition brought people out to view the submarine and meet the crew, more attention than the company usually enjoys at its home port, Perry said.

“The community response was excellent, and it far exceeded our expectations and far exceeded the attention we get in Everett,” he said.

“It was great to see people come down to the dock at Fort Worden, and we did impromptu tours for several folks.”

The OceanGate team spent about 11 hours over four days surveying the Governor.

Perry said the company had planned to conduct two dives per day for two hours each but adjusted the schedule to make the best use of the tides and currents.

“We did a fair amount of 2-D [two-dimensional] and 3-D sonar scans and multiple hours of video — so much so that I’d like to tell you what’s there, but we haven’t seen it all,” he said.

Perry said OceanGate will team up with the Jefferson County Library, the Jefferson County Historical Society Museum and the Northwest Maritime Center for a public presentation at 6:30 p.m. Aug. 4 at the maritime center.

“I’m very confident we have enough video and 2-D and 3-D sonar to tell the story of the expedition and see the current condition of the wreck,” Perry said.

The Governor, though recognizable — chiefly because the sea floor is flat and no other wrecks are nearby — is severely deteriorated from having been in the sea for 90 years.

“The condition of the wreck is decaying,” Perry said.

“Huge sections have collapsed, and you can see exposed ribs. Most of the plating is worn away or fallen off.

“It’s definitely recognizable as a wreck.”

The crew did observe artifacts on the sea floor — some plates, a bathroom sink and an anchor — but the ship itself has succumbed to the sands of time.

The girth of the Governor is so large that the Antipodes expedition captured perhaps a quarter to a half of the entire ship on video and sonar.

But the goal wasn’t to produce a comprehensive scan of the Governor. It was to conduct a field test away from OceanGate’s home port in Everett.

What was learned here will be applied to a dive to the SS Montebello later this year off the California coast.

The Montebello was torpedoed on Christmas Day in 1941 by a Japanese submarine and sank within 25 minutes off the coast south of Monterey.

The 38-member crew survived, but 73,000 barrels of crude oil may yet be aboard the vessel.

OceanGate will survey the wreck to assess the potential environmental threat to the nearby Monterey Bay National Marine Sanctuary and report its findings to the National Oceanic and Atmospheric Administration.

OceanGate learned better methods for doing sonar scans during the expedition to the Governor.

For instance, the sonar scans have to be stitched together akin to piecing together a panorama photo from multiple images.

Computer programs that assist in that effort need reference points on the images in order to accurately piece them together.

Perry said the team tested the variables of distance from the ship and distance between scans in order to discover the optimal combinations.

In the dark depths below the surface, it’s difficult to visually pick out reference points, so the team may place objects around the Montebello to have more success with sonar scanning.

“I would say that operationally, it was a huge success,” Perry said.

“A big part of our agenda was being mobile and operating away from home.”

But a lot of the work is yet to come, though OceanGate’s team has some down time this coming week because of the Fourth of July holiday and the need to conduct annual inspections and repairs on the Antipodes submarine.

“We’re doing the annual maintenance and go over standard safety protocol, similar to what scuba divers do,” Perry said.

“We inspect the tanks and run through all the electricals and wiring and do a full assessment.

“We were very pleased [with the operation of the Antipodes]. We had some computer issues, but not with the operation of the sub.”

Perry lauded the haulout work done by Sea Marine at Point Hudson.

“It was a great expedition for the team and great to see the community support and the Sea Marine team was excellent,” he said.

“I would love to come back some day and scan the entire wreck.”

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Philip L. Watness is a freelance writer and photographer living in Port Townsend. He can be reached at whatnews@olypen.com.