RAIM Prediction

[Barry]

Is there a site that provides online RAIM predictions for the US? I know
that Flight Service is supposed to be able to provide this, but it would be
nice to have another source.

Barry

[ArtP]

On Thu, 2 Oct 2003 15:03:41 -0400, "Barry" > wrote:

>Is there a site that provides online RAIM predictions for the US? I know
>that Flight Service is supposed to be able to provide this, but it would be
>nice to have another source.

A GNS 430/530 will provide it.

[Barry]

> >Is there a site that provides online RAIM predictions for the US? I know
> >that Flight Service is supposed to be able to provide this, but it would
> >be nice to have another source.
>
> A GNS 430/530 will provide it.

Yes, I should have added that I can get it from the receiver (our club
recently installed a GNS 430), but I 'm looking for a source I can use
during preflight.

Barry

[Michael 182]

Not that it isn't a good idea, but in about 1000 hours flying with a GNS 430
I've experienced maybe 15 minutes of RAIM "failure", (at least that I've
noticed) and even during those 15 minutes the data was still accurate. In
addition, no failure lasted more than a minute or so.

Michael




"Barry" > wrote in message
...
> > >Is there a site that provides online RAIM predictions for the US? I
know
> > >that Flight Service is supposed to be able to provide this, but it
would
> > >be nice to have another source.
> >
> > A GNS 430/530 will provide it.
>
> Yes, I should have added that I can get it from the receiver (our club
> recently installed a GNS 430), but I 'm looking for a source I can use
> during preflight.
>
> Barry
>
>
>

[karl gruber]

******Yes, I should have added that I can get it from the receiver (our club
recently installed a GNS 430), but I 'm looking for a source I can use
during preflight.****

Download the Garmin 430 simulator!



http://www.garmin.com/products/gns430/

[Scott Lowrey]

I'm an IFR rookie, but I just happened to have read a bit about RAIM last
night.

If I can speak on behalf of Barry, he's asking for RAIM _predictions_ for a
certain route (or the whole country). RAIM availability is not a constant;
you can't get it from a simulator because it's subject to real-world
variables. You can't get RAIM forecasts from a receiver, right? The
receiver can only confirm integrity "right now". Later on, the required
five satellites may not be available due to things like scheduled service
outages and atmospheric conditions. Wouldn't want to find that out at
arrival time.

To quote Jeppesen:

"In practice, the easiest and most reliable way to ensure that you will have
RAIM for the approach at your ETA is to specifically request GPS RAIM
availability from your FSS weather briefer."

Still, I would echo the question: where do the briefers get this info?

-Scott

[ArtP]

On Fri, 03 Oct 2003 01:51:51 GMT, "Scott Lowrey" >
wrote:

> You can't get RAIM forecasts from a receiver, right? The
>receiver can only confirm integrity "right now".

You can get RAIM forecasts from a receiver (or the simulator). It
knows where all of the satellites are located at any time in the
future. If you provide a location to the RAIM and a time to the RAIM
prediction screen, it will tell you if the satellite geometry will
give you satisfactory reception. It will not tell you if a satellite
is scheduled to be out or DOD is jamming (that is the function of
NOTAMs). Nothing will tell you if there will be an unscheduled outage
because of equipment failure or atmospheric conditions. That is why
all IFR certified GPS systems must provide RAIM warnings.

[Jon Parmet]

"Scott Lowrey" > wrote in message news:<XC4fb.482201$Oz4.324450@rwcrnsc54>...
[snip]
> To quote Jeppesen:
>
> "In practice, the easiest and most reliable way to ensure that you will have
> RAIM for the approach at your ETA is to specifically request GPS RAIM
> availability from your FSS weather briefer."
>
> Still, I would echo the question: where do the briefers get this info?

From the output of a prediction model which is run (at least once)
daily at the NOCC.

> -Scott

Regards,
Jon

[karl gruber]

****Still, I would echo the question: where do the briefers get this
info?***


From the Garmin 430 simu;lator!

[Tarver Engineering]

"ArtP" > wrote in message
...
> On Fri, 03 Oct 2003 01:51:51 GMT, "Scott Lowrey" >
> wrote:
>
> > You can't get RAIM forecasts from a receiver, right? The
> >receiver can only confirm integrity "right now".
>
> You can get RAIM forecasts from a receiver (or the simulator). It
> knows where all of the satellites are located at any time in the
> future. If you provide a location to the RAIM and a time to the RAIM
> prediction screen, it will tell you if the satellite geometry will
> give you satisfactory reception.

Immagine that every pair of satellites with you as the third point defines
circle. When multiple circles line up, there is not enough time difference
to make a calculation. The signal is unaffected.