Question: I’ve noticed that sometimes when I am sailing, especially on starboard tack, my GPS seems to stop giving my location. My speed over the ground and course made good information is also lost. What could be causing this?
Answer: As good as GPS technology has gotten over the last decade, it still has one fundamental need: the receiving antenna must have a clear “view” of the sky above. If the antenna can’t receive data from the satellites in the system, all the information needed for position finding and speed data won't get to your GPS’s computer.
Placement of the GPS “hockey puck” antennas on boats almost guarantees that the signal will be blocked during normal boat maneuvering and operation. Just look at the photo: the white disk mounted just behind the winch on this cruising sailboat is the GPS antenna. Now, consider that in normal sailboat use, a helmsperson or crew member will probably sit on top of the coaming. In that case the only view the GPS is going to have is of a particular backside. You get the idea.
A lot of electronics installers are techies with no clue about actual boat operation, so they sometimes mount this equipment in easy to install spots that may or may not have the best view of the sky on a boat underway.