[LINK] Ffx: 'Farmers ‘crippled’ ... as GPS-guided tractors grind to a halt'

[Carl Makin]

> On 19 Apr 2023, at 5:20 pm, Kim Holburn <kim at holburn.net> wrote:
> 
> I haven't read all this yet but how could this all possibly depend on just one satellite?  One satellite would only be above the horizon for half of the time.  How would that even work?
> 
> When I look at GNSS satellites ATM I see 80 at any one time.  That includes US GPS, Chinese BDS, Russian Glonass, European Galileo, Indian IRNSS/Navic, Japanese QZSS.

The satellite that went down was in geostationary orbit.  It was providing GPS correction signals for not only Geoscience’s SBAS open pilot, but for proprietary correction systems from Trimble and others across the whole asia/pacific region (along with other stuff like aircraft voice and data coverage over the ocean).

The GPS receivers use GPS, Galileo, Glonass LEO satellites etc for the primary location signal which is accurate to about 10m, then the corrections from the Inmarsat satellite to refine that fix down to, in this case, less than 10cm.


Carl.