[Boatanchors] LightSquared

[J. Forster]

> GPS by design can detect lack of accuracy; this can be done, since
> multiple solutions can be determined using different satellites; a cross
> check can identify errors.

GPS does a 'best fit' to minimize the error from all available solutions.
The data to do this comes from satellite ephemeris, and range and range
rates to the birds.

> I don't know much about LORAN to know how it could compute multiple fixes
> to detect errors.

Exactly the same way. You compare the fixes from all available
Master-Slave pairs. One pair gives you a hyperbola of possible locations;
a second pair gives you a second hyperbola; the intersection is your
location. A third pair will give you two cross checks, and so on. A modern
receiver could, under computer control, can easily look for additional
cross checks from other chains with diffeing GRIs. It's a simple
autocorrelation problem.

GPS has improved, largely to the increasing power of uPs, which enables
far more computation.

-John

=============


Cross check with what? A GPS signal?
>
> I know that LORAN is more than aviation, but I am familiar about aviation.
>
> FL
>
> -----Original Message-----
> From: J. Forster [mailto:jfor at quikus.com]
> Sent: Tuesday, October 09, 2012 8:14 AM
> To: Francesco Ledda
> Cc: 'Drew P.'; boatanchors at mailman.qth.net
> Subject: RE: [Boatanchors] LightSquared
>
>> The problem with LORAN was that there was no way to detect an error
>> and/or degradation of accuracy; this limited its use for aviation
>> application to enroute applications.
>
> Well, since the potential shutdown was known for many years, no
> manufacturer
> was inclined to make the design effort to write the SW to provide cross
> checks. A chicken & egg problem.
>
> Also, LORAN-C was never designed to be an ILS. It was certainly good
> enough
> to get you within a mile of your destination.
>
>> LORAN had some problems when closing in to bad storms. I did
>> experience the LORAN going "blank" at the "wrong time" due to heavy
>> statics, few times; it is not fun, when flying.
>
> Again, flying is NOT the one and only use.
>
>> I still think that E-LORAN will come back one day.... may be, it is
>> wishful thinking.
>>
>> FL
>
> IMO, it will require a government that takes terrorism seriously or
> another
> 9/11 type incident.
>
> "Ossama Bin Laden is dead,
> Al Queda is aliuve and well."
>
> -John
>
> =================
>
>