A unit of the U.S. Strategic Command is conducting classified Global Positioning System tests in waters off Kauai that could disrupt civilian GPS systems on land and sea.

The tests are designed to "assess the capabilities and vulnerabilities of joint coalition forces in a degraded and denied environment" — meaning military test subjects will have their GPS units affected as if they were driving through a tunnel, said Navy Lt. Cmdr. Stephanie Murdock of the U.S. Strategic Command, based in Omaha, Neb.

Murdock declined to describe how or where the tests are being conducted by the Joint Navigation Warfare Center — or what the tests are trying to determine.

"For security reasons, we can’t discuss that," she said.

Murdock insisted that the tests are not intended to disrupt civilian GPS units.

The Coast Guard, however, does ask people experiencing any GPS problems to contact its Coast Guard Navigation Center in Virginia at 703-313-5900 or by completing a GPS problem reporting form on the center’s website at www.navcen.uscg.gov.

Petty Officer 2nd Class Eric Chandler, a Coast Guard spokesman, could not say whether GPS owners who contact the Coast Guard will have their problems resolved — or whether the Coast Guard is merely collecting data for the tests.

"There’s nobody in the Coast Guard that can speak on that," Chandler said.

Neither the Navy nor the Coast Guard could say whether anyone in Hawaii has reported GPS problems since the tests began.

THE Coast Guard announced the series of tests to be conducted from Aug. 19 to Sunday in a news release that initially referred to a point of contact with the Navy.

But the Navy said it didn’t know anything about the operation. A second Coast Guard announcement listed another Navy contact, who also knew nothing about the tests.

The Navy referred questions about the GPS tests back to the Coast Guard.

Murdock finally responded to questions on Friday.

The first of three tests, which overlap, began Aug. 19 and runs from 3 to 8 p.m. and from midnight to 4 a.m. through Sunday. That testing is being done within a radius of about 70 miles from a point about 55 miles north-northwest of the Pacific Missile Range Facility at Barking Sands.

The second test, which also began Aug. 19 and ends Sunday, and is being conducted between the hours of 8 p.m. and 4 a.m. in a radius of 342 miles around Barking Sands. That extends all the way to Hilo.

The third began Aug. 20 and is being conducted from midnight to 4 a.m. through Sunday within a radius of about 490 miles from a point about 20 miles northwest of Barking Sands. That covers all major Hawaiian Islands.