In a paper in the May 1996 issue of this Journal, Ward and Johannessen gave an excellent summary of the work carried our for the General Lighthouse Authorities on the significance of potential interference to GPS. They identified three possible types of interference for their study:
(i) Interference from other systems on board the ship using GPS.
(ii) Interference from emissions generated onboard other ships or at structures in the vicinity of the ship using GPS.
(iii) Deliberate interference from malicious persons.
