Those at sea in the vicinity of the Middle East might be brushing up on their nav today. A good reminder that GPS is very easy to deny and can't be solely relied on.

www.abc.net.au/news/2024-09-22/israel-gps-s****ing-lebanon-beirut-hezbollah/104373018?utm_source=abc_news_app&utm_medium=content_shared&utm_campaign=abc_news_app&utm_content=link

Yeah!!! Sail on the Red Sea I reckon you be dead.

Not a new problem.
There is video somewhere of Grant Dalton carrying a sextant down the dock to board NZ endeavour in a Whitbread.
First Gulf War from memory.

Besides GPS is not navigation, just an aid to navigation.

And for those with a mathematical bent, it is fun to practice old school.





Mucking around and taking distance off Mt Hardgrave on Stradbroke island.
Surprisingly accurate. (About 150m in 10 miles after working out the errors when checked against GPS afterwards, the maths was done on a mobile phone)
Sextant is excellent and brought on Gumtree for $350.00
Made in East Germany before unification.

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lydia said..
Made in East Germany before unification.

The guy who introduced me to sailing had joined the RN as a boy in the mid-forties. His sextant (into the 1980's) was recovered from a German U-boat.

Fun fact - the Royal Navy had first dibs on anything that floated at the end of the war. The young officers did their sail training on Goring's boat Marabu - one of the "windfall" yachts.

Selective Availability during the first Gulf war was still an issue. The USA was then able to down grade or switch off GPS availability to all bar the military. Nowadays too much (and not just navigation) is reliant on GPS and selective availability was abandoned decades ago. Add to that many other countries and organizations - including Australia use satellite constellations not controlled by the US.
GPS certainly has become more than just an aid for navigation. Now the information that the GPS signal is overlaid upon is a different story.
Electronic (GPS) jamming in a war zone is a different matter again. But if you were that close that 'they' are jamming your signal you are probably to close to the action anyway.

Worth forking out for a system that accesses multiple constellations?

AKA GNSS.

As you would be well aware, GPS is just 1 constellation that the USA own. And they may well have the ability to turn SA back on, but I bet they can't do that to Galileo, Beidou or even better yet Glonass.

A GNSS system would use all 5 constellations whereas a GPS unit uses, well just the GPS constellation.

They come at a price though

I use a cheap Garmin Etrex 10 handheld GPS unit, was about $130, now apparently discontinued.

It uses signals from GPS as well as Glonass (Russian system). I thought it did Galileo also (European) but am mistaken.
You don't need to pay a lot of money for a GPS with other satellite system inputs.

And then is the 98 Hobart Team Jag radio exchange!
Freaky stuff.

I surprised that some think that in GNSS denied area like the Red Sea mentioned, the other countries constellation systems wouldn't be affected. Here's todays jaming map with Red Sea in the lower red part.

No, I very specifically stated that 'jamming' was a different issue to Selective Availability. Sure the end result is the same, you'll be reaching for the paper charts

Toph, understood. I was just trying to show the GNSS denial has moved from a tool used by the superpowers to a capability that many countries have and use regularly as can be seen by the effort civil aviation sites use to track it.

Keeping paper charts and a hf radio on my boat. I know its old tech but I will set up a pactor modem I bought off gumtree too. Although I think I have seen apps that will do the job of the modem now that you can just download. Have to check it out, anyway I like the idea of added redundancy.

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EastCoastSail said..
Toph, understood. I was just trying to show the GNSS denial has moved from a tool used by the superpowers to a capability that many countries have and use regularly as can be seen by the effort civil aviation sites use to track it.

Sorry ECS, I misinterpreted your post

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lydia said..
Not a new problem.
There is video somewhere of Grant Dalton carrying a sextant down the dock to board NZ endeavour in a Whitbread.
First Gulf War from memory.

Besides GPS is not navigation, just an aid to navigation.

And for those with a mathematical bent, it is fun to practice old school.





Mucking around and taking distance off Mt Hardgrave on Stradbroke island.
Surprisingly accurate. (About 150m in 10 miles after working out the errors when checked against GPS afterwards, the maths was done on a mobile phone)
Sextant is excellent and brought on Gumtree for $350.00
Made in East Germany before unification.

Nice pick up. Wow looking on the net good real ones not cheap.. I kick myself I gave away my Davis 25 . I still have an old plastic ebbco which was accurate enough for doing vertical fixes and also using horizontally to get the angle between two or three objects and transferring to the chart.