The lighthouse, built in 1868, was a navigational aid until about 1900.

"I know that's just a navigational aid, but it's probably sending contact reports to that base. "

The light is still in use as a navigational aid.

But in an earlier era, the light was a much-needed navigational aid.

This feature was a navigational aid for airliners of the time.

They are working to restore the lighthouse, which is still an active navigational aid.

Much attention has been focused on the fact that a key navigational aid was out of service for maintenance.

The lighthouse is currently in use as a navigational aid.

In another, she helped mark water towers with town names as a navigational aid for pilots.

Most birds use the direction of the sun more than any other navigational aid, and so need a very reliable time sense.