Problem with a satellite

M

MiskinDriver

Well-Known Member
Joined
17 Jan 2007
Messages
298
Location
London
Visit site
Posted this in the Lounge 'cos its general, but this may be a better place?

My Alpine GPS sat nav in the car failed a couple of weeks ago - refusing to boot up. Having tried reinstalling everything, I finally gave up and took it to a dealer. They instantly knew what the problem was. Their explanation is:

The particular model of GPS I have uses a small number of reference satellites as part of the boot process. One of the ones used by this system has recently expired and been replaced (around 3 - 4 weeks ago) by a new one to maintain the constellation. Unfortunately, the software does not recognise this new satellite ident, and thus will not boot. They say they have spoken at length to Alpine in the UK, and they advise that the engineers in Japan are working on a software fix, but that this may be weeks before it is available. My only alternative to waiting for the fix is to buy a new controller with new CD for around £900.

Questions are:

a) anybody else heard of this?
b) am I being conned?
c) does this affect any of the main marine GPS systems?
 
Hi

The US coastgaurd publish a constantly updated list of satelite outages and they will e-mail you if you subscribe to their to their mailing lists when a satelite is offline or being repaired.

I dont have the site adress at the mo but if you google noa or uscg satelites you will find their site.
 
Scroll further down to see a pretty amazing piece of video of a disabled yacht in heavy surf, and fantastic helicopter rescue. WOW
 
Err I thought this kind of rubbish behaviour was long gone.


Although the GPS may have trouble starting , needing up to 30 minutes to 1 hour to boot (if all stored data has been wiped like last position, temperature calibration curves etc) , the process of starting up should be ...

Using a pre-programmed list of satellites, scan through all of them. When _one_ is found decode its data to obtain a list of _current_ satellites and then use (Almanac) this to replace the preprogrammed list to speed search for the remainder. When three satellites are found can get time and date and lat/long assuming sea level or last remembered altitude (2D fix) . From time and date predict fairly accurately where the other satellites are. When fourth satellite is found then you know the altitude (3D fix) . From each of the satellites data one can then extract the ephemeris to get the position of the satellite to better accuracy . From then on more satellites simply improve the accuracy of the fix.


The process of changing GPS satellites has happened many times over the years. No modern GPS should give up.

Five years ago I used to work on the software in the core of a GPS receiver.

Suspect a hardware fault like no GPS aerial connection.
 
Thank you all for taking the trouble to reply to this. In some cases, I even understood the reply. I thought I was reasonably technologically literate, but at moments like this I just go to 'tilt' mode.

The hardware was OK, but it now appears that the latest excuse for the failure from Alpine is its to do with the 29th of February....... they weren't expecting a leap year?

Ah well, that'll be £900 down the drain then.
 
You must log in or register to reply here.

Share this page

Top