Ah, the Link Institute scores again.
On 19 Apr 2023, at 5:20 pm, Kim Holburn <[email protected]> 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.
On 19/4/23 5:45 pm, Carl Makin wrote:
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.
The reporter dramatised this bit, but mis-phrased it, resulting in at
least Roger mis-reading what had happened:
> Tractors ... are enabled with GPS tracking and can be guided to an
accuracy within two centimetres ... All that went out the window when
the Inmarsat-41 satellite signal failed.
So "all that" is misleading, and would be better as 'they lost the
refinement from +/10m [?] to +/- <10cm (and maybe even +/- 2cm?)'.
--
Roger Clarke mailto:[email protected]
T: +61 2 6288 6916 http://www.xamax.com.au http://www.rogerclarke.com
Xamax Consultancy Pty Ltd 78 Sidaway St, Chapman ACT 2611 AUSTRALIA
Visiting Professor in the Faculty of Law University of N.S.W.
Visiting Professor in Computer Science Australian National University
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