It is currently Tue Jun 25, 2019 8:23 pm


Post new topic Reply to topic  [ 11 posts ] 
Author Message
PostPosted: Sun Mar 10, 2019 6:10 pm 
Offline

Joined: Fri Dec 03, 2004 9:58 pm
Posts: 3508
Location: Wellingborough
"Are we facing a GPS failure in all of our modern tech devices?"

Posted by Dr. Clay Sherrod of the Arkansas Sky Observatories on the ASO site:

http://arksky.org/calendar/alerts/820-i ... s-location

Seems the answer is "Don't Panic" :D

First I've heard of this possible apocalypse scenario. Well I thought it was interesting :shock:

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


Top
 Profile Send private message  
 
PostPosted: Mon Mar 11, 2019 7:15 am 
Offline

Joined: Sun May 11, 2008 6:11 pm
Posts: 3186
Location: Portslade, Sussex Lat 50deg 51min Long 0deg 13mins West
Hm. I certainly have not been worrying about it and having refered to the Internet page, I must admit I still do not understand it! Regards maf


Top
 Profile Send private message  
 
PostPosted: Mon Mar 11, 2019 7:48 pm 
Offline

Joined: Fri Dec 03, 2004 9:58 pm
Posts: 3508
Location: Wellingborough
Hi Mike. There is a more user-friendly discussion of the potential "problem" here:

https://www.gps-repeaters.com/blog/gps- ... -6th-2019/

HTH,

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


Top
 Profile Send private message  
 
PostPosted: Wed Mar 20, 2019 10:10 pm 
Offline

Joined: Fri Dec 10, 2004 10:34 pm
Posts: 348
Location: Surrey
I checked my Garmin 35 GPS receiver that I use for occultation timings and one of the NMEA sentances is reporting the date as 1999 ! However some of the software appears to ignore this and must use the computer clock to get the correct date.

LLooking at the output with GPSMON this reports the date today as June 1963 ! The logfile shows that it thinks there is a negative date - not sure how this is calculated.

The other interesting thing is that as the GPS is reporting a 1999 date it is showing a magnetic deviation of 3.2 degrees W when in reality the deviation at my location is now very close to zero.

In terms of the week number roll over there has been remarkably little publicity - bearing in mind how many systems now use GPS time I can see quite a few stopping on the 6th April 2019. For information the rollover occours at 18 secs to midnight on the 6th April. The 18 seconds is due to the fact GPS time is 18 seconds in advance of UTC as it is monotonic and therfore does not have leap seconds. The GPS system transmits the number of seconds difference between GPS Time & UTC so that users get the correct UTC time.

I would have thought the government would have taken action to ensure GPS systems are tested but other than a couple of sites warning shipping of possible problems I have seen very little. Perhaps this is another example of where the government has taken its eye off the ball due to the B******* distraction.

_________________
Engineer @ Work - Astronomer @ Play


Top
 Profile Send private message  
 
PostPosted: Thu Mar 21, 2019 4:52 pm 
Offline

Joined: Fri Dec 03, 2004 9:58 pm
Posts: 3508
Location: Wellingborough
The Government are relying on the Armed Forces being able to navigate by the Sun, stars and by dead-reckoning I think :lol:

As for in-car navigation, I still use maps :wink:

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


Top
 Profile Send private message  
 
PostPosted: Fri Mar 22, 2019 8:25 am 
Offline

Joined: Fri Dec 10, 2004 10:34 pm
Posts: 348
Location: Surrey
Brian,

Not sure you can navigate modern aircraft by the stars - early 747's still had a sextant port in the top of the cockpit but no longer. I doubt if military aircraft are fitted now - the air sextants from the V Bomber era are all for sale on a surplus site in Devon.

GPS does a lot more including providing timing for the stability of the electricity supply as well as telling trains that they are at platforms so they can opent the doors.

It was used for financial transaction timing but that has been superceded within Europe by time from an EU fibre optic system - GPS was not good enough.

John

_________________
Engineer @ Work - Astronomer @ Play


Top
 Profile Send private message  
 
PostPosted: Fri Mar 22, 2019 4:39 pm 
Offline

Joined: Mon Jan 18, 2010 9:25 am
Posts: 5267
The air sextants, possibly WW2, contain an awful glass phial for illumination.
Radioactive beads, perhaps hundreds. They sent my monitor off scale screaming instantly.

Some seem to have this hazard removed, but I had one or two complete.

They were still using WW2 radar in the V bombers (H2S?), so it wouldn't surprise me if the sextants were the same.

Modern pilot training now includes stellar navigation, so pilots should know how to do this.
The real problem is that they don't know how to fly without computers.

Regards,
David


Top
 Profile Send private message  
 
PostPosted: Fri Mar 22, 2019 5:13 pm 
Offline

Joined: Fri Dec 03, 2004 9:58 pm
Posts: 3508
Location: Wellingborough
This thread was from 2015:

viewtopic.php?f=2&t=19711

_________________
Brian
52.3N 0.6W
Wellingborough UK.

254mm LX90 on Superwedge, WO ZS66SD, Helios 102mm f5 on EQ1, Hunter 11x80, Pentax 10x50
ASI120MC Toucam Pros 740k/840k/900nc mono, Pentax K110D
Ro-Ro roof shed


Top
 Profile Send private message  
 
PostPosted: Fri Mar 22, 2019 6:09 pm 
Offline

Joined: Fri Dec 10, 2004 10:34 pm
Posts: 348
Location: Surrey
David,

Attached is an image of the Aerial Sextant in a Vulcan I took last year.

The ones for sale are at https://www.trinitymarine.co.uk/shop/pe ... rnborough/ (other suppliers are available !)

They look similar except the one in the Vulcan is missing the large handle though the arrow remains. The other odd thing is the Vulcan one appears to have the eyepiece on the left and the one in the adver on the right.

Quite a bargin compared to the proper sextants on the site. They have some nice minature sextants used on RAF flying boats - at a price !

John


Attachments:
20180822-140820-small.jpg
20180822-140820-small.jpg [ 239.08 KiB | Viewed 551 times ]

_________________
Engineer @ Work - Astronomer @ Play
Top
 Profile Send private message  
 
PostPosted: Sat Mar 23, 2019 5:12 pm 
Offline

Joined: Mon Jan 18, 2010 9:25 am
Posts: 5267
Hi John,
This is different to the astro compasses that I had.
I see an astro compass is for sale with the radioactive bead phial removed. I hope that none are for sale with these beads.

My name is on the bomb door of the last flying Vulcan, as I supported the team, until I got fed up with their record keeping

I used to record daily sightings of Valiants, Victors and some Vulcans in the 1950s.
Up to 63,000 ft cruise. This may have been a camera equipped Victor without the heavy bomb load.
A Vulcan reputedly got up to over 80,000 ft with no bomb load and low fuel, until it glided back to base.
Also U.S. 10 engined B36s, 6 engined B47s etc. These flew lower.
Apparently, these daily sorties were for real with live bombs.

A Canberra took photos of a U2 at operational height from above the U2.
The Canberras just could not be reached by early Migs.
I went into a Canberra when in the cadet force, but unfortunately not on a flight.

Regards,
David


Top
 Profile Send private message  
 
PostPosted: Sat Mar 23, 2019 7:08 pm 
Offline

Joined: Fri Dec 10, 2004 10:34 pm
Posts: 348
Location: Surrey
David,

It is a sextant rather than a compass. From a bit of the manual that is online I think it uses 3V for the internal illumination and 28V for the heater for the top window that is outside the aircraft.

Earlier versions used an internal bubble for level but I beleive this version uses a damped pendulum with a mirror acting as the horizon. The large 'knob' missing on the one in the Vulcan is I suspect the winder for the mechanical averaging mechanism.

I might visit them and buy one when I am next in Devon.

John

_________________
Engineer @ Work - Astronomer @ Play


Top
 Profile Send private message  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 11 posts ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 5 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group