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Comment by _moof | Hacker News Reader

Fog doesn't affect GPS. GPS is just not 100% reliable (ask me how I know) or necessarily even the best navaid for every situation. Even aircraft go visual for the last few hundred feet. (Or if they're doing autoland, it's with a purpose-built ground-based system, not GPS.)

Speaking more generally it's just very risky to put all your eggs into one basket when it comes to navigation. It's so difficult to impress upon the new generation of navigators that they are guaranteed to be completely screwed at least once in their lives if they don't learn something other than GPS.

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> guaranteed to be completely screwed

Looking at years of MAIB reports I'd say that the thing which you're guaranteed to be "completely screwed" by sooner or later is negligence: https://www.gov.uk/maib-reports

The technology used pales in comparison, a man comfortably asleep in a nook on the bridge at 0300 is equally oblivious to a lighthouse, urgent radio calls from the coastguard, GPS monitoring or anything short of being shaken awake by the vibration when the ship smashes into something.

> GPS is just not 100% reliable (ask me how I know)

How to you know?

As OP hasn't replied yet, I'll take the liberty. The biggest issue is interference (jamming) by malicious actors. This is especially common in the eastern Mediterranean [1]. Earlier this year there have also been reports of interference on Finland's border with Russia [2].

Of course one could imagine other scenarios where GPS might become inaccurate or unavailable on a larger scale, such as an attack on the satellites themselves.

[1] https://safety4sea.com/us-marad-gps-interference-incidents-r...

[2] https://www.traficom.fi/en/news/unusual-amount-reports-about...

(my guess is that _moof is a navigator with experience in the eastern med sea)

in android, the GPS config file (some xml) file will do the trick of making the at least the GPS/Location system on the phone unreliable. Apparently each country has their own config file. Found this out when a friend used the Android bought in China in US. So no GPS is NOT reliable for critical situations, it is more a consumer connivence ATM.

Nope. It's maps in China that are unreliable. On purpose. https://www.serviceobjects.com/blog/why-gps-coordinates-look...

It is not that I do not know that GPS is unreliable. But I wanted to read about what OP had experienced specifically.

> The biggest issue is interference (jamming) by malicious actors.

And not necessarily malicious. Before I ditched Strava (insert separate rant about tech "ecosystems"), one of my bike rides took me near a nuclear power plant. The resulting GPS track had a sudden hundreds-of-feet "climb" near the power plant that didn't exist in the real world, as if I had literally climbed a wall on my bike.

I wanted to dim the chart plotter. I turned it off: was the same button, required a push of a different length. If I wasn't aware of where my bow was pointed and what I was trying to do at the time, it would have been a big problem, particularly in traffic. But because I knew where I was and what I was doing I was able to continue to sail and turn everything back on.

> ask me how I know

How do you know?

>ask me how I know

How do you know?

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