If you compass says something is 39 degrees, it is actually closer to 28 degrees true. A final resort is to wait for a clear night and find Polaris , the North Star . From a specific place on your lanai or other antenna site, make a note of what is directly below that star, such as a telephone pole. The UH Manoa Bookstore sells a terrific map for one of the Anthropology courses that is a detailed map of the Pacific about the size of a sheet of legal paper, but containing all the political boundaries of the various South Pacific Island groups and most of the important islands. They also have individual Hawaiian island maps with latitude and longitude lines on them.
Hams there are often surprised to talk to someone who actually knows where they are located.