GPS locator question

Okay, I am unsure if such a device works as I list below, but I am
hoping someone out there can give me a couple of ideas on where to
look...

WHAT I WANT: I transponder/receiver pair such that I can mount the
transponder in my dive flag styrofoam and have the receiver display
heading and distance to the flag. For example, my dive flag has the
transponder, and my wife has the receiver in the boat, and merely by
looking at the receiver she will know where I am.

I do not want one of the 1970's era systems where the receiver is a
funky antenna that you swing back and forth to test signal strength,
and only indicates heading. I am thinking something along the lines of
the transponder being a device that has a GPS antenna and FM
transmitter, and sends out its current GPS coordinates every 30
seconds or so via FM signal. The receiver is an FM receiver that can
receive the signal, a GPS antenna that can pull the coordinates down
for the receiver, and a small computer than can then take the
coordinate location of the receiver and the coordinate location of the
transponder, do some simple math, and determine heading and distance.

Does such a thing exist? I would prefer it not be a kit, but rather an
out-of-the-box solution. Thanks for the help ahead of time!

P.S. I have a portable GPS unit and a laptop, and can link the two for
the receiver part (assuming I can get the appropriate receiver).

Joe Granto wrote:
> Okay, I am unsure if such a device works as I list below, but I am
> hoping someone out there can give me a couple of ideas on where to
> look...
>
> WHAT I WANT: I transponder/receiver pair such that I can mount the
> transponder in my dive flag styrofoam and have the receiver display
> heading and distance to the flag. For example, my dive flag has the
> transponder, and my wife has the receiver in the boat, and merely by
> looking at the receiver she will know where I am.
>
> I do not want one of the 1970's era systems where the receiver is a
> funky antenna that you swing back and forth to test signal strength,
> and only indicates heading. I am thinking something along the lines of
> the transponder being a device that has a GPS antenna and FM
> transmitter, and sends out its current GPS coordinates every 30
> seconds or so via FM signal. The receiver is an FM receiver that can
> receive the signal, a GPS antenna that can pull the coordinates down
> for the receiver, and a small computer than can then take the
> coordinate location of the receiver and the coordinate location of the
> transponder, do some simple math, and determine heading and distance.
>
> Does such a thing exist? I would prefer it not be a kit, but rather an
> out-of-the-box solution. Thanks for the help ahead of time!
>
> P.S. I have a portable GPS unit and a laptop, and can link the two for
> the receiver part (assuming I can get the appropriate receiver).

The technology exists and has for quite awhile. I know of no commercial
products for that specific an application. Many portable GPS units send
out a data stream that can be transmitted, received, decoded, and
interpreted onto a map. Ham operators have been doing this for years
with units in their vehicles (APRS).

"Joe Granto" <joe.granto@NoSpam.com> wrote in message
news:hrds93lqqigstpq5aded2gln4b10gri2l2@4ax.com...
> Okay, I am unsure if such a device works as I list below, but I am
> hoping someone out there can give me a couple of ideas on where to
> look...
>
> WHAT I WANT: I transponder/receiver pair such that I can mount the
> transponder in my dive flag styrofoam and have the receiver display
> heading and distance to the flag. For example, my dive flag has the
> transponder, and my wife has the receiver in the boat, and merely by
> looking at the receiver she will know where I am.
>
> I do not want one of the 1970's era systems where the receiver is a
> funky antenna that you swing back and forth to test signal strength,
> and only indicates heading. I am thinking something along the lines of
> the transponder being a device that has a GPS antenna and FM
> transmitter, and sends out its current GPS coordinates every 30
> seconds or so via FM signal. The receiver is an FM receiver that can
> receive the signal, a GPS antenna that can pull the coordinates down
> for the receiver, and a small computer than can then take the
> coordinate location of the receiver and the coordinate location of the
> transponder, do some simple math, and determine heading and distance.
>
> Does such a thing exist? I would prefer it not be a kit, but rather an
> out-of-the-box solution. Thanks for the help ahead of time!
>
> P.S. I have a portable GPS unit and a laptop, and can link the two for
> the receiver part (assuming I can get the appropriate receiver).

********************
http://web.usna.navy.mil/~bruninga/aprs.html
http://www.aprs.net/
http://www.cave.org/aprs/
http://www.ew.usna.edu/~bruninga/iss-faq.html
http://www.winaprs.org/
http://www.aprsfl.net/
********************
I just checked on the FCC rules for using FRS/GMRS radios for the link, and
they can be used for digital data providing the remote link(marker float),
is not used as a continous beacon. The base/mobile unit can "query" the
remote and the rmote will "acknowledge" with position data in APRS format.
Good, flat beam-tilt antennas at both ends should allow solid communications
over calm water for over a 20 miles radius, on 1 watt or less.
This can be done quite easily, but some "fudging" of the FCC rules may be
necessary to achieve long distances without licensing the operators for GMRS
operation. (2 watts).
I can probably put one set together for about $600, but that won't include
any labor.
***********************

From a buddy of mine who forgot more about RF than any of us ever want to
know.

nitespark wrote

> WHAT I WANT: I transponder/receiver pair such that I can mount the
> transponder in my dive flag styrofoam and have the receiver display
> heading and distance to the flag. For example, my dive flag has the
> transponder, and my wife has the receiver in the boat, and merely by
> looking at the receiver she will know where I am.

I'm quite sure it exists. Many companies that find it convenient to track
their truck or car fleet use systems that will do what you want. The only
question is whether it's worth it to you.

Lee

On Wed, 18 Jul 2007 12:01:20 -0400, Joe Granto <joe.granto@NoSpam.com>
wrote:

>Okay, I am unsure if such a device works as I list below, but I am
>hoping someone out there can give me a couple of ideas on where to
>look...
>
>WHAT I WANT: I transponder/receiver pair such that I can mount the
>transponder in my dive flag styrofoam and have the receiver display
>heading and distance to the flag. For example, my dive flag has the
>transponder, and my wife has the receiver in the boat, and merely by
>looking at the receiver she will know where I am.
>
>I do not want one of the 1970's era systems where the receiver is a
>funky antenna that you swing back and forth to test signal strength,
>and only indicates heading. I am thinking something along the lines of
>the transponder being a device that has a GPS antenna and FM
>transmitter, and sends out its current GPS coordinates every 30
>seconds or so via FM signal. The receiver is an FM receiver that can
>receive the signal, a GPS antenna that can pull the coordinates down
>for the receiver, and a small computer than can then take the
>coordinate location of the receiver and the coordinate location of the
>transponder, do some simple math, and determine heading and distance.
>
>Does such a thing exist? I would prefer it not be a kit, but rather an
>out-of-the-box solution. Thanks for the help ahead of time!
>
>P.S. I have a portable GPS unit and a laptop, and can link the two for
>the receiver part (assuming I can get the appropriate receiver).

The APRS solution might work, but for the ham band stuff you would
need an amateur radio license. Most of the APRS stuff seems to consist
of components like pocket GPS, a TNC, and a 2 meter radio for the data
link. The Kenwood handheld looks promising:
http://www.kenwoodusa.com/products/L...&k3=11&pr=2137


If you are not too far off shore and still have cellular coverage
where you dive you could put a GPS equipped cell phone like the newer
Blackberry 8800 series in a waterproof plastic box. Then schedule the
laptop to query the phone about it's location as a tracking request.
The laptop could then compute distance and bearing to the target based
on the two GPS positions. This has the advantage of small size,
completely self contained in one unit, no license required and works
world wide. Stuffing a $400 phone into a float might be a bit pricey
for some, but if you have a boat and let your wife drive it while you
dive, I don't think price is an object for you. :)

On Thu, 19 Jul 2007 02:55:58 GMT, Geoff <geoff@invalid.invalid> wrote:
> Stuffing a $400 phone into a float might be a bit pricey
> for some, but if you have a boat and let your wife drive
> it while you dive, I don't think price is an object for
> you. :)

The last (and only) time that Grace drove my boat, she drove over the
ski tow line and sucked it up in the jet impeller... Luckily, we were
out on the lake with a friend who was on his jet ski and he was able
to tow us back to the dock... It took about an hour or so to get it
untangled one I had it home and could get it up high enough to be able
to work underneath it... There was a *lot* of rope tangled in there...
Of course it was *my* fault even though I had repeatively told her to
*not* cross the rope... I'm sure that there are some women somewhere
that can be trusted to pilot a boat... I've just never met one...

Geoff wrote

> If you are not too far off shore and still have cellular coverage
> where you dive you could put a GPS equipped cell phone like the newer
> Blackberry 8800 series in a waterproof plastic box. Then schedule the
> laptop to query the phone about it's location as a tracking request.
> The laptop could then compute distance and bearing to the target based
> on the two GPS positions. This has the advantage of small size,
> completely self contained in one unit, no license required and works
> world wide. Stuffing a $400 phone into a float might be a bit pricey
> for some, but if you have a boat and let your wife drive it while you
> dive, I don't think price is an object for you. :)

Actually, it does not work world wide unless you have the right kind of
phone and the phone service set up world wide. The signal travels via the
cell phone system. Worse, cell phone service is, at best, spotty only a few
miles off shore and even more unreliable from a phone located close to the
surface. How many bars do you get?

If the purpose is for safety, you have a couple options. One is a personal
locating beacon, basically a compact EPIRB. Another, probably less expensive
option might be a small GPS, and a hand held VHF radio. If you reach the
surface and the boat's not visible, you can call the boat and give them your
location. If the boat's visible, which it normally would be, you can use
your compass and give it a heading. If your boat's nowhere to be found, you
can call other boats. If the VHS has the DSC feature, it will talk to the
GPS and, in an emergency, broadcast your location to any boat on the right
frequency, including official search and rescue agencies.

Lee

Lee

"Scott" <pugetsounddiver@gmail.com> wrote in message
news:RbadnR-kQaOHLQPbnZ2dnUVZ_vCknZ2d@whidbeytel.com...
> "Joe Granto" <joe.granto@NoSpam.com> wrote in message
> news:hrds93lqqigstpq5aded2gln4b10gri2l2@4ax.com...
> > Okay, I am unsure if such a device works as I list below, but I am
> > hoping someone out there can give me a couple of ideas on where to
> > look...
> >
> > WHAT I WANT: I transponder/receiver pair such that I can mount the
> > transponder in my dive flag styrofoam and have the receiver display
> > heading and distance to the flag. For example, my dive flag has the
> > transponder, and my wife has the receiver in the boat, and merely by
> > looking at the receiver she will know where I am.
> >
> > I do not want one of the 1970's era systems where the receiver is a
> > funky antenna that you swing back and forth to test signal strength,
> > and only indicates heading. I am thinking something along the lines of
> > the transponder being a device that has a GPS antenna and FM
> > transmitter, and sends out its current GPS coordinates every 30
> > seconds or so via FM signal. The receiver is an FM receiver that can
> > receive the signal, a GPS antenna that can pull the coordinates down
> > for the receiver, and a small computer than can then take the
> > coordinate location of the receiver and the coordinate location of the
> > transponder, do some simple math, and determine heading and distance.
> >
> > Does such a thing exist? I would prefer it not be a kit, but rather an
> > out-of-the-box solution. Thanks for the help ahead of time!
> >
> > P.S. I have a portable GPS unit and a laptop, and can link the two for
> > the receiver part (assuming I can get the appropriate receiver).
>
> ********************
> http://web.usna.navy.mil/~bruninga/aprs.html
> http://www.aprs.net/
> http://www.cave.org/aprs/
> http://www.ew.usna.edu/~bruninga/iss-faq.html
> http://www.winaprs.org/
> http://www.aprsfl.net/
> ********************
> I just checked on the FCC rules for using FRS/GMRS radios for the link,
and
> they can be used for digital data providing the remote link(marker float),
> is not used as a continous beacon. The base/mobile unit can "query" the
> remote and the rmote will "acknowledge" with position data in APRS format.
> Good, flat beam-tilt antennas at both ends should allow solid
communications
> over calm water for over a 20 miles radius, on 1 watt or less.
> This can be done quite easily, but some "fudging" of the FCC rules may be
> necessary to achieve long distances without licensing the operators for
GMRS
> operation. (2 watts).
> I can probably put one set together for about $600, but that won't include
> any labor.
> ***********************
>
> From a buddy of mine who forgot more about RF than any of us ever want to
> know.

More from Mr. RF:

************************
OR....use a couple of these at $260 a copy:

http://gpsonsale.com/garmin/products...6DNg-WCHd2pdXT

************************

Joe Granto <joe.granto@NoSpam.com> wrote:
>
> WHAT I WANT: I transponder/receiver pair such that I can mount the
> transponder in my dive flag styrofoam and have the receiver display
> heading and distance to the flag. For example, my dive flag has the
> transponder, and my wife has the receiver in the boat, and merely by
> looking at the receiver she will know where I am.


In other words, you want a GPS that transmits its location, and a way to
receive that location signal, right?


Such a product exists.


It is currently used in commercial shipping and essentially works by
sending the GPS data through Marine VHF Radio, where other
similarly-equipped systems can receive the data.


It is called the Automatic Identification System (AIS)

See:
http://www.navcen.uscg.gov/enav/ais/default.htm


> I would prefer it not be a kit, but rather an
> out-of-the-box solution.

Class A systems are an "out-of-the-box" solution, but you'll probably
not like the price tag, plus I don't think that you'll meet all of the
carriage requirements to be legally allowed to use one, see

Title 33 CFR, 164.46 - Automatic Identification System (AIS).

There's a Class B system that's apparently been approved, but devices
are not yet available as per the US Coast Guard's website, above.


FYI, there's also a similar system that exists for aviation. A coworker
who has a small C172 owns & uses one, but I'm not sure how it does its
data dissemination: I think that this system might rely on Air Traffic
Control to be the data retransmission relay agent?


Briefly looking through some webpages to try to find system costs, it
looks like it would cost around $500 to add AIS **receive-only**
capability to a boat's existing Radio & GPS system. This would infer
that the AIS transmit side is significantly more expensive.


-hh

On Thu, 19 Jul 2007 05:48:18 -0400, "Lee Bell"
<pleebell@bellsouth.net> wrote:

>Actually, it does not work world wide unless you have the right kind of
>phone and the phone service set up world wide. The signal travels via the
>cell phone system. Worse, cell phone service is, at best, spotty only a few
>miles off shore and even more unreliable from a phone located close to the
>surface. How many bars do you get?

Which is why I predicated it on being close enough to shore that you
have cell coverage and why I recommended the BB:
http://www.blackberry8800series.com/

T-Mobile and Cingular/AT&T are currently selling this model. Opinions
about coverage vary. The GPS is built in and the phone can be queried
for its location via the cell network. It does CDMA and GSM/GPRS on
all relevant bands.

Another nice feature is it has mapping built in so you will know which
direction to paddle when she doesn't pick you up. :) Stuff some
earphones into the waterproof box and you can listen to your favorite
tracks while waiting for the rescue chopper. (Don't turn it up too
loud or you will run the battery down or miss the pleasing sound of
Sea Stallion turbines and the whuff whuff of her blades.)

I used my 7320 in China in 2005 and had better coverage there via
China Mobile than I did in the US on T-Mobile. I suspect the Chinese
had the Germans build them a world-class cell net. It sure as hell
wasn't an American designed system. The company paid the tab so I
don't know what messaging cost but I had four or more bars everywhere
I went, including cruising down the Yangtze river and the Three Gorges
dam. I even had cell coverage several miles out of Guilin surrounded
by picturesque limestone mountains.

Once you get more than 1 or 2 miles off shore you will very likely
have zero signal on the surface of the water. In that case your only
solution is the handheld GPS/Packet radio/APRS system and a direct
link between the boat unit and the float. Even then the propagation is
line of sight at 144MHz so it won't work beyond a few miles anyway but
you would have no dependency on shore-based radios. Licensing becomes
an issue but with the advent of no-code Technician class you can crack
a study guide and be licensed in a few weeks.