Re: Why this GPS?

Valued Customer (gempsm@clemson.campus.mci.net)
Wed, 7 Oct 1998 17:54:11 -0400


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West Wight Potter Website at URL
http://www.lesbois.com/wwpotter/
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Sorry, another "two cents" worth. Before you get too excited remember most
of the GPS units like Garmin and Mag. receive the satellite signals using
the SPS or Standard Positioning Service. There are other formats, PPS,
etc. which are much more expensive and some require additional hardware.
All this being said, the guaranteed accuracy under SPS is 100 meters. It
is usually much more accurate, but all depends on how much clock timing
error the Government has introduced at the particular time of use. So as
someone has already pointed out, if you have visual reference, use that
chart, take some compass bearings, plot them out and get you an accurate
fix. Check against your GPS for obvious error. We can bet a little more
in year 2001 or 2 when the government puts up those extra satellites and
the general public can purchase the new units which will have accuracy in
the 10 meter area. The old ones will still work, but under the existing
system. Don't gamble your big investment with the small. (GPS unit)
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> From: Russell Lahti <Russell_Lahti@nps.gov>
> To: wwpotter@tscnet.com; Rdement1@aol.com
> Subject: Why this GPS?
> Date: Thursday, October 08, 1998 10:00 AM
>
> Russ,
>
> I am intrigued by the accuracy you say you get with your GPS. Would

> you please tell me what the make, model and so on is for your unit.

> Why did you buy this one instead of another? Can you upload and
> download data (way points/lat-log etc.) from your PC?
>
> Any comments, advice or experience anyone else wants to share would
be
> appreciated.
>
>
> Thanks,
>
> Russell Lahti
>
>
> ______________________________ Reply Separator
_________________________________
> Subject: Re: Calculated Hull Speed of P-19
> Author: Rdement1@aol.com at NP--INTERNET
> Date: 10/7/98 4:18 AM
>
>
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> West Wight Potter Website at URL
> http://www.lesbois.com/wwpotter/
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> In a message dated 10/6/98 9:41:32 PM Pacific Daylight Time,
katze@nidlink.com
> writes:
>
> << I am under the impression that a GPS cannot give a reliable speed
> determination under 15 mph? >>
>
>
> Sometimes true, sometimes not. When the GPSIII gets into "3D mode"
(position
> +altitude), it is extremely accurate. (except altitude, which seems to
have a
> 300ft tolerance no matter what!)
>
> When I walk with it in my hand, it almost always reads 3 or so mph with
> acurate compass. When I stop it reads 0.0mph. Sometimes it will
fluctuate
> around 1mph. In my vehicle, I compare it at 20mph against the police
radar
> leaving the gate of US Navy Submarine Base Bangor, WA it always reads
> identical..
>
> There are many factors that affect GPS. S/A being the most influential
of
> course. No matter how much we may hate the government influencing 'our
toys',
> we are still tapping into 'their system'. (We just paid for it) The same

> system that guided 75 of our missiles a month or so ago within feet of
their
> targets. And the same system that may be 'shut off', or deliver
misleading
> information to keep 'non-friendly birdies' from coming within feet of
our
> backyards using our system against us.
>
> As everyone else who has put a large sum of money into their gps toys, I
would
> like mine to be as accurate as it possibly can. BUT, I still wouldn't
solely
> rely on it. GPS is a good ocean navigation tool. If you can't see any
land,
> it will give your approximate position. If you can see land, you are
better
> off taking a visual fix, and plotting on a NOAA chart. The same way every
US
> Navy ship (surface and sub) is still required to do. GPS (military
grade) and
> LORAN are only a reference for them.
>
> GPS is more accurate than what most will give credit. I have a waypoint
> programmed for my driveway. When I drive to work, to the mall, to the
boat
> ramp, etc then come home.... I am always within 10 feet of my exact lat
and
> long........ toys toys toys........
>
> Russ de Ment
> borrowed grandpas P-19
> Silverdale, WA
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> From: Rdement1@aol.com
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> Date: Wed, 7 Oct 1998 04:18:44 EDT
> To: wwpotter@tscnet.com
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> Subject: Re: Calculated Hull Speed of P-19
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