Re: WAAS for Garmin 295

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"Ron Lee" <ronlee@pcisys.net> wrote in message
news:3ae3b067.3733610@news.pcisys.net...
> "Tarver Engineering" <jtarver@sierratel.com> wrote:
> >
> >There is a plan to activate GPS Enroute using L2 when the constellation
is
> >50% populated in November. With L2 you will have 0.2 meter accuracy and
> >none of the expense associated with populating a useless WAAS
constellation.
> >UPS is now driving the LAAS (VHF Digital Radio) initiative in order to
> >penetrate Asian markets. We could see portable CAT I next year.
> >
> >John
>
> GPS en route for a RNP-2 RNAV route structure does not need L2. First
> off there will not be a 50% constellation woth civil L2 in November.

Yes in fact there will be a 50% populated GPS IIf constellation in place as
of November. The Aircraft Electronis Association and the Airlines have
already given notice of intent to begin using L2 then. The GPS
constellation is on a 26 month replacement cycle.

> I don't know the FIRST launch date of a IIR with L2 but I can state
> with certainty that you will not have 12 on orbit this year. It may
> be one but I am not certain of thet.

What is GPS IIR?

> And you will not have 0.2 meter accuracy. Assuming an HDOP of 1.0,
> that would put the UERE ( signal in space plus user equipment error)
> at 0.1. Again not likely anytime soon.

The military does it now.

> Getting back to en route, 0.2 meter horizontal is overkill and
> unnecessary. The SIS requirement is 0.74 km. GPS can do that now
> with very high availability. Add in baro-aiding and RAIM availability
> is also very high.

The 0.2 L1 + L2 error eliminates any claim by WAAS promoters that it
improves accuracy and the failure of the program to produce a working
integrity eliminates any other claims of value for WAAS. If the system had
been operating in October of 1998 as it was supposed to then there would
have been a need for WAAS, but when SA was turned off that all ended.

The WAAS program out of Washington announced at the LAACO DER conference
that they did not expect to have a working system until 2015.

John

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