Thread: something for you oldies

Is it any wonder you were not invited to lecture on the subject, Saitch?

Originally Posted by spudfan

Great respect for Mr Len Beadell. One of a kind.
I remember when GPS was first introduced. I was working as a land surveyor at the time. GPS was initially an American military system. When it was introduced to the public it had a built in error, which was fairly substantial to my mind. This was to stop terrorist and other unsavoury characters using it for nefarious purposes! I could get a more accurate fix using a theodolite than the then extant GPS system. Albeit it took a bit of time and using tables and a hand calculator. I had a Casio FX scientific unit at the time. Anyway the accuracy of the GPS system has much improved over the years with the "safety" error removed.
Anyway this book is great reading..if you like this sort of thing. If you are a budding Len Beadle you will find it highly interesting. If you want to learn about GPS, well you are out of luck as it predates all of that.

I think the US still "relaxes" the accuracy of GPS in their war zones, and I have heard the theory that they've altered GPS borders to lure terrorists into a different country where a drone strike is less problematic.

Originally Posted by RANDLOVER

I think the US still "relaxes" the accuracy of GPS in their war zones, and I have heard the theory that they've altered GPS borders to lure terrorists into a different country where a drone strike is less problematic.

Unless the GPS system has changed significantly I don't believe that's feasible.

Selective Availability (which was the method whereby Civilian GPS had a broader definition of accuracy) was either on or off. It was switched off for the First Gulf war, then permanently in 2000. It hasn't been turned back on and as of 2007 any satellite deployed doesn't have the capability.

Because of the way the constellation works, there is no ability to alter timing characteristics being directed at certain locations, and having to try and coordinate 8 or more satellites to lie at the same time, but only while passing over a specific geographic region (even if technically possible) would cause timing disturbances that would be globally flagged immediately. Just like the temporary disabling of SA in the first Gulf War. News got around real quick when the boffins all noticed their fixes became more accurate.

Originally Posted by BradC

Unless the GPS system has changed significantly I don't believe that's feasible.

Selective Availability (which was the method whereby Civilian GPS had a broader definition of accuracy) was either on or off. It was switched off for the First Gulf war, then permanently in 2000. It hasn't been turned back on and as of 2007 any satellite deployed doesn't have the capability.

Because of the way the constellation works, there is no ability to alter timing characteristics being directed at certain locations, and having to try and coordinate 8 or more satellites to lie at the same time, but only while passing over a specific geographic region (even if technically possible) would cause timing disturbances that would be globally flagged immediately. Just like the temporary disabling of SA in the first Gulf War. News got around real quick when the boffins all noticed their fixes became more accurate.

You're pro'ly right and the outcomes I mentioned are more likely to be done by GPS jamming or spoofing.

GPS Jamming in Ukraine - Space News & Breaking Defense - RNTF (rntfnd.org)

And the reason being.....

I dont know if mobile phone gps co ordinates are correct yet but they were wrong.

I found this out while working with a marine rescue service and co-ordinates sent to us by boaties needing assistance put us miles out when we responded and put the boaties in risk.

I forget what it is now but before we left base our radio operator usually applied a simple formula to check/correct co-ordinates given from the boaties mobile phone.

I think it was a digital>analogue conversion needed

I still never use one no matter where I go , prefer the Mk11 eyeball and dead reckoning.

Originally Posted by ramblingboy42

I dont know if mobile phone gps co ordinates are correct yet but they were wrong.

I found this out while working with a marine rescue service and co-ordinates sent to us by boaties needing assistance put us miles out when we responded and put the boaties in risk.

I forget what it is now but before we left base our radio operator usually applied a simple formula to check/correct co-ordinates given from the boaties mobile phone.

I think it was a digital>analogue conversion needed

I still never use one no matter where I go , prefer the Mk11 eyeball and dead reckoning.

A fair chunk of that probably came from errors or miss communication of decimal or min/sec coordinates, or translating between survey datums (GDA94 etc).

Originally Posted by cjc_td5

A fair chunk of that probably came from errors or miss communication of decimal or min/sec coordinates, or translating between survey datums (GDA94 etc).

Which is why these days there's a link to allow connecting the GPS to the back of the VHF. Push that emergency Chan 16 button and it'll transmit the current coords as part of the emergency call. Takes one of the weak links out of the comms chain ( an operator under duress).