Loss of GPS fix due to military activity?

  • Thread starter Thread starter Deleted User YDKXO
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Deleted User YDKXO

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We are currently berthed in La Spezia in Italy and the marina is close to an Italian navy base. Last week I was inputting a set of waypoints into our lower helm plotter when the plotter suddenly lost it's GPS fix. I tried rebooting the plotter and requesting a GPS restart, changing between GPS antennas (we have 2 onboard) and trying the flybridge plotter but still no GPS fix. By luck I happened to mention it to a German neighbour and he said he had experienced the same thing and when I discussed it later with a local man, he said that it was likely due to some kind of activity in the adjacent naval base and that it happened regularly. Sure enough when we motored out of the harbour, after a couple of miles, the plotters picked up a GPS fix again.
I've never heard of such a thing happening. Has anyone else? I know the military can do what it wants but has it a right to carry out activities which jam GPS fixes on other vessels without warning? I made a point of listening to the navigational warnings on Genoa radio afterwards (broadcast in English) and no warning was mentioned. The real point is this. La Spezia is a busy commercial port; surely it is a major risk to commercial shipping in the area for GPS signals to be lost without warning?
 
Happens regularly in approaches to Napoli also and is related to high power electronic transmission apparently, usually by military. Most commercial shipping does not rely on GPS solely for navigation position fixing. We use the eyeball, echo sounder, fixed navigational marks such as buoys, beacons, radar parallel indexing and in some ports pilots are available to assist. Deep sea we still have sextants available and some hyperbolic nav systems might be used e.g.Loran.

Always be ready for GPS position fixing to fail, it should be used as an aid to navigation.And it does usually fail at the most unwelcome moment!

s1975
 
S1975 said:
Happens regularly in approaches to Napoli also and is related to high power electronic transmission apparently, usually by military. Most commercial shipping does not rely on GPS solely for navigation position fixing. We use the eyeball, echo sounder, fixed navigational marks such as buoys, beacons, radar parallel indexing and in some ports pilots are available to assist. Deep sea we still have sextants available and some hyperbolic nav systems might be used e.g.Loran.

Always be ready for GPS position fixing to fail, it should be used as an aid to navigation.And it does usually fail at the most unwelcome moment!
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We all know we are not supposed to rely on GPS as a primary source of navigation but we all know that most of us do it all the same and a sudden loss of this information could be the difference between grounding the boat and not grounding it, particularly at night. Personally I always have a paper chart and pilot book in front of me when entering an unfamiliar harbour and I'm also eyeballing navigational marks and cross referencing them to what I see on the plotter and paper chart, as well as using the radar and sounder but the unexpected loss of a GPS fix would definitely cause me some stress. The question really was not about reliance on GPS but whether the military should be causing loss of GPS fix without prior warning?
 
Deleted User said:
The question really was not about reliance on GPS but whether the military should be causing loss of GPS fix without prior warning?
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They should not and usually do not. The UK military certainly issues NOTAMS when the are playing. In Italy, it may be Belesconi's TV transmitters, they provided lots of problems for GPS in the 1990's.
 
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