NetNews Usenet Archive 1992 #31/NN_1992_31.iso/spool/rec/boats/8826

Text File | 1992-12-30 | 3.2 KB | 67 lines

Newsgroups: rec.boats
Path: sparky!uunet!newsgate.watson.ibm.com!yktnews!admin!avalon!dwl
From: [e-mail] (David W. Levine)
Subject: Re: GPS fix quality (was: Celestial vs. GPS )
Sender: [e-mail] (NNTP News Poster)
Message-ID: <[e-mail]>
Date: Wed, 30 Dec 1992 21:05:29 GMT
Reply-To: [e-mail]
Disclaimer: This posting represents the poster's views, not necessarily those of IBM
References:  <[e-mail]>
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Organization: IBM Thomas J. Watson Research Center
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In article <[e-mail]>,
[e-mail] (Dudley Knappe) writes:
|>
|> |>[e-mail] (Kees Verruyt) writes:
|> |>|> [e-mail] (Robert Hanners) writes:
|> |>|> Also there's the direct ability to calculate potential error due to
|> |>|> nearly parallel intercepts and of course the unit can get a direct read
|> |>|> on signal strength.
|> |>|>
|> |>|> My question is this: Why isn't it reasonable for the unit to
calculate and
|> |>|> display a measure of this potential error, as individual values (for
|> |>|> the discerning user :-) ) or as a total?  Or is this in fact a feature
|> |>|> of some makes?  The error itself could be a statistical measure such
|> |>|> as 50%, standard deviation, 2 x sd, or whatever.  Preferrably such
|> |>|> weighting would be user selectable.
|> |>
|> |> You're quite right -- and so think some of the GPS manufacturers since I
|> |>remember that at least one brand has the ability to display such an
|> |>error-value.  Don't remember which one though. I probably saw it at the
|> |>Paris (France) Boat Show, where I must have seen at least 20 different
|> |>brands of GPS equipment.
|>
|>     I worked with Stu Bell's Magellan 5000 GPS while crossing the Gulf of
|> Mexico.  There was a diagnostic mode that you could bring up that displayed
|> the quality (strength, signal/noise ratio) of the satellite signal on
a scale
|> of 0-10, 0 being the worst, 10 the best; and the quality of the fix
from that
|> satellite (again, 0-10).  Once I understood what it was trying to
tell me, it
|> was much easier to discern whether a fix was trustworthy or not, or even how
|> bad it might be.
|>
|> --
|> Dudley Knappe, Software Development Division            Cray Research, Inc.
|> Phone: [phone]                                   655F Lone Oak Drive
|> E-mail: [e-mail] or uunet!cray!dudley            Eagan, MN 55121

For what it's worth, that's one of the things I do poke at with most lorans,
if the box lets me check it. Most boxes include this and it's worth learning
how to call it up and what it means. For example, on one boat I race on,
the Loran's generally cranky while charging heavily. On my folks boat, we had
to re-cable the VHF run into the Nav station to keep the VHF from killing the
Loran when trasnmitting. Understanding what your unit can tell you about itself
is useful.


David W. Levine --  [e-mail]  -- IBM Thomas J. Watson Research Center
                   -- My Opinions, IBM's hardware. --
"Fanaticism consists in redoubling your efforts when you have forgotten your
aim" - George Santayana