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| Subject: | Re: [gislist] GPS underwater |
| Date: |
09/23/2003 11:20:01 AM |
| From: |
Steven M. Robertson |
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Two other sources of interference for the GPS satellite signal is the
troposphere, which contains water droplets that reflect the GPS signal
(causing distortion of the signal) and rain, which can have a similar
effect, although with today's receivers I've noted if the rain consists of a
slight downpour or thundershower emanating from low lying clouds, often you
can still collect points. If you have an upper level disturbance causing
rain that may well introduce enough water droplets to effectively block the
GPS signal altogether. One other thing, most GPS receivers are NOT
waterproof. Traditionally the survey and mapping grade receivers are water
resistant. The manufacturer reps will tell you they are made to withstand a
slight drizzle, however some of the less-expensive units on the market, like
the Gamin Etrex, is advertised as waterproof...I surmise that is only for
those of us who are clumsy like myself and tend to drop things in unlikely
places:)
----- Original Message -----
From: "Bill Diaz" <william.diaz@comcast.net>
To: <arcgis@lists.directionsmag.com>
Cc: <gislist@lists.thinkburst.com>
Sent: Monday, September 22, 2003 7:59 PM
Subject: RE: [gislist] GPS underwater
> A GPS receiver cannot function if the antenna is under water. The water
> completely blocks the GPS signals.
>
> I have heard of underwater GPS applications, but the antenna was mounted
on
> a buoy floating on the surface. Excessive wave height can block access to
> all available satellites, and the wave action itself can cause the GPS to
> supply somewhat erratic data. If the underwater object is moving, the
> antenna cable must be longer than the depth of the object. This means
that
> the antenna will not be directly above the object. Similar effects will
be
> observed in the presence of high winds or currents.
>
> Bill
>
> >-----Original Message-----
> >From: gislist-bounces@lists.geocomm.com
> >[mailto:gislist-bounces@lists.geocomm.com] On Behalf Of bader nader
> >Sent: Monday, September 22, 2003 12:11
> >To: arcgis@lists.directionsmag.com
> >Cc: gislist@lists.geocomm.com
> >Subject: [gislist] GPS underwater
> >
> >
> >hi
> >dose any one have information about using GPS
> >underwater
> >
> >regards,
> >
> >
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