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PA2AGA > HDDIG 08.04.00 08:02l 215 Lines 7247 Bytes #-9517 (0) @ EU
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Date: Mon, 3 Apr 2000 16:48:42 -0700
From: Fred Ramsing <framsing@unr.edu>
Subject: Will a GPS provide continuous, accurate altitude measurements?
With selective availability on (reduces accuracy), and using an 8-channel
GPS receiver can obtain a horizontal accuracy of 100 meters with a 95%
confidence provided that four satellites are in view. That means that
there is a 95% chance that you are 100 meters from the reported location.
Vertical accuracy is usually 1.5 times the horizontal accuracy, about 173
meters with a 95% confidence. Reasonably priced receivers can have 8
channels for simultaneous comparisons; don't waste your money on
channel-switching receivers - they are not worth the drop in price.
With differential GPS you can get down to 10m at 95% confidence, but that
requires a dedicated base station. Sub-meter accuracy can be obtained
with differential GPS, but only with prolonged recordings - this is for
surveying purposes.
Yep, I think the previous suggestion to use an altimeter is a lot
better. My watch gives 20 ft accuracy at 95%, about 6 meters.
*******************************************
* Fred Ramsing *
* Graduate Program in Hydrologic Sciences *
* University of Nevada, Reno *
* framsing@unr.edu *
*******************************************
Differential GPS can yield
On Mon, 3 Apr 2000, Dante wrote:
> I'd like to be able to drive around in my car, and get a close-to continuous
> reading on my altitude above sea level. Will a GPS do this? Is it fairly
> accurate and precise? If not, is there a reasonably priced item that would
> do this?
>
> What if I interfaced the GPS with something like TOPO USA?
>
> Thanks
>
>
>
>
------------------------------
Date: Mon, 3 Apr 2000 17:17:19 -0700
From: "Jim Donohue" <jim_donohue@computer.org>
Subject: Will a GPS provide continuous, accurate altitude measurements?
Or he might try the new Garmin Etrex which apparently has a built in
barometer.
I wonder if they fed it into the filter? Be interesting to see how that
would work.
Jim
Gary Coffman <ke4zv@bellsouth.net> wrote in message
news:1t7iescr95ob09i3oq8bvobs7euvhhlu0n@4ax.com...
> On Mon, 03 Apr 2000 17:07:53 GMT, "Dante" <dante@theinferno.com> wrote:
> >I'd like to be able to drive around in my car, and get a close-to
continuous
> >reading on my altitude above sea level. Will a GPS do this? Is it
fairly
> >accurate and precise? If not, is there a reasonably priced item that
would
> >do this?
>
> Most handheld GPS receivers aren't very accurate in altitude
determination.
> An error of 500 feet is not uncommon, depending on the satellite geometry
> of the members of the GPS constellation that are visible from your
location
> at any given moment. A normal altimeter (barometer) would probably serve
> your purpose better. Many of the auto accessories places carry them, or
> you could get one from an aircraft salvage yard.
>
> Gary
> Gary Coffman KE4ZV | You make it |mail to ke4zv@bellsouth.net
> 534 Shannon Way | We break it |
> Lawrenceville, GA | Guaranteed |
------------------------------
Date: Tue, 04 Apr 2000 04:39:00 GMT
From: "D. Stussy" <kd6lvw@bde-arc.ampr.org>
Subject: Will a GPS provide continuous, accurate altitude measurements?
Note: The 173m vertical inaccuracy is equivalent to about 550 feet, which was
mentioned in an earlier response.
On Mon, 3 Apr 2000, Fred Ramsing wrote:
> With selective availability on (reduces accuracy), and using an 8-channel
> GPS receiver can obtain a horizontal accuracy of 100 meters with a 95%
> confidence provided that four satellites are in view. That means that
> there is a 95% chance that you are 100 meters from the reported location.
> Vertical accuracy is usually 1.5 times the horizontal accuracy, about 173
> meters with a 95% confidence. Reasonably priced receivers can have 8
> channels for simultaneous comparisons; don't waste your money on
> channel-switching receivers - they are not worth the drop in price.
>
> With differential GPS you can get down to 10m at 95% confidence, but ....
------------------------------
Date: Mon, 03 Apr 2000 17:26:50 +0200
From: Morgan Gunnarsson <di98gumo@chl.chalmers.se>
Subject: XTAL BP-filter ??
Is it possible to construct a BP-filter by using a XTAL,
where the filter's middle freq. equals the XTAL's resonans freq.?
Morgan
------------------------------
Date: Mon, 03 Apr 2000 15:30:36 GMT
From: Robert <romapa@earthlink.net>
Subject: XTAL BP-filter ??
Yes- it is done all the time. Run a search on 'crystal filter'.
Morgan Gunnarsson wrote:
> Is it possible to construct a BP-filter by using a XTAL,
> where the filter's middle freq. equals the XTAL's resonans freq.?
>
> Morgan
------------------------------
Date: Mon, 03 Apr 2000 08:52:11 -0700
From: Huffy <uhflink@yahoo.com>
Subject: XTAL BP-filter ??
In article <38E8B83A.BCDA39A5@chl.chalmers.se>, Morgan Gunnarsson
<di98gumo@chl.chalmers.se> wrote:
> Is it possible to construct a BP-filter by using a XTAL,
> where the filter's middle freq. equals the XTAL's resonans freq.?
>
> Morgan
Crystal filters tend to have very narrow bandwidth. If you want a filter
for wideband FM, then you'll need something else.
--Huffy
eperated in frequency by the desired degree of
bandpass.
--
73, Cecil, W6RCA http://www.mindspring.com/~w6rca
------------------------------
Date: Tue, 04 Apr 2000 11:12:28 +1000
From: "Russ.Shaw" <russell@webaxs.net>
Subject: XTAL BP-filter ??
By coupling identical hi-Q resonators such as crystals together with
the right amount of coupling, the bandwidth is made wider and can have
the usual butterworth/tchebyshev shapes etc. A certain limit is determined
by the stray parrallel capacitance of the crystals. Using transformers, these
parallel stray effects can be suppressed to make even better filters.
W6RCecilA wrote:
>
> Morgan Gunnarsson wrote:
> > Is it possible to construct a BP-filter by using a XTAL,
> > where the filter's middle freq. equals the XTAL's resonans freq.?
>
> That particular approach usually results in a filter so narrow
> that modulation data is distorted. A better approach is to use
> two XTALs seperated in frequency by the desired degree of
> bandpass.
> --
> 73, Cecil, W6RCA http://www.mindspring.com/~w6rca
--
*******************************************
* Russell Shaw, B.Eng, M.Eng(Research) *
* Electronics Consultant *
* email: russell@webaxs.net *
* Australia *
*******************************************
------------------------------
End of Ham-Digital Digest V2000 #95
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