On Thu, 28 Oct 2004 17:07:46 -0400, Rodney Myrvaagnes
wrote:

The latter is a relevant concern. I haven't seen a recent GPS that had
a problem at walking speed or even slower, but they do say where you
are actually going, not your heading.

The difference can be considerable in areas with strong currents.

Especially if your engine is in reverse! :-)

Dave

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would
give good resolution down to at least 2 to 3 knots.

Exactly Kevin Monahan's point. At low speed, creeping through fog, you will
not get a stable heading readout. I have a Garmin 182C plotter with WAAS.
Below 2 knots I start to see the "compass" heading wandering.
Kevin's book is quite recent and takes into account the current situation.
I'm planning on purchasing the Raymarine Seatalk/NMEA conversion box so that
I can feed my Autohelm fluxgate compass heading to my JRC radar. The JRC
has two NMEA inputs, one for GPS and one for Compass. Internal software
selects the Compass heading input over any GPS heading input.
Maybe this isn't necessary a lot of the time but I'd like to be able to rely
on what the radar is showing at all times.

"Bruce in Alaska" wrote in message
...
In article tZRfd.10435$df2.5362@edtnps89,
"Gordon Wedman" wrote:

In " The Radar Book - Effective Navigation and Collision Avoidance " by
Kevin Monahan, he points out that the compass bearing given by a GPS will
be
unstable at low speeds. If you want your radar to show proper compass
bearings and work in the North-up/Course-up modes he says you must
connect
to some type of fluxgate or gyro compass. So if you just connect your
GPS
NMEA output to your radar it seems you may not get correct heading
information while creeping along at low speed, for example, in fog.

That would very much depend on the GPS, its Position Update Rate, and
internal Math Capabilities. I would suspect that any GPS that updates
faster than every .5 Sec, and has a good floating point processor, would
give good resolution down to at least 2 to 3 knots.

Bruce in alaska
--
add a 2 before @

When will GPS compasses come down in price? Just came from the bridge of an APL
container ship where they had two Sperry GPS compasses. They have replaced mech
gyros on many ships and are very accurate and responsive. Cost about $17,000.00
each.

On Sat, 23 Oct 2004 17:25:47 GMT, Bruce in Alaska
wrote:
I am under the impression that ARP is and add on option for all the
small commercial Furuo Radars. I am not 100% sure on that exact model
(1833) but I bet Doug could give us a difinitive answer.

============================================

I just got back from the Ft Lauderdale boat show and had a chance to
talk with the Furuno factory reps. It turns out that ARP functions on
the 1833 are possible but require an optional circuit board that costs
about $600 or so. No where is the circuit board mentioned in the list
of 1833 options on the Furuno web site and several dealers I've talked
to were not aware ot it either. There is also an additional circuit
board available that accepts composite video input and allows it to be
displayed either full screen or in a window.

In article ,
Wayne.B wrote:

On Sat, 23 Oct 2004 17:25:47 GMT, Bruce in Alaska
wrote:
I am under the impression that ARP is and add on option for all the
small commercial Furuo Radars. I am not 100% sure on that exact model
(1833) but I bet Doug could give us a difinitive answer.

============================================

I just got back from the Ft Lauderdale boat show and had a chance to
talk with the Furuno factory reps. It turns out that ARP functions on
the 1833 are possible but require an optional circuit board that costs
about $600 or so. No where is the circuit board mentioned in the list
of 1833 options on the Furuno web site and several dealers I've talked
to were not aware ot it either. There is also an additional circuit
board available that accepts composite video input and allows it to be
displayed either full screen or in a window.


Yep, that squares with my memory. ARP is a seperate function that must
be added on to any of the small commercial Furuno Radars. Once you get
into the Big Boat Stuff it is built in, but the cost are significant.


Bruce in alaska
--
add a 2 before @

"Wayne.B" wrote in message
news
On Sat, 23 Oct 2004 17:25:47 GMT, Bruce in Alaska
wrote:
I am under the impression that ARP is and add on option for all the
small commercial Furuo Radars. I am not 100% sure on that exact model
(1833) but I bet Doug could give us a difinitive answer.

============================================

I just got back from the Ft Lauderdale boat show and had a chance to
talk with the Furuno factory reps. It turns out that ARP functions on
the 1833 are possible but require an optional circuit board that costs
about $600 or so. No where is the circuit board mentioned in the list
of 1833 options on the Furuno web site and several dealers I've talked
to were not aware ot it either. There is also an additional circuit
board available that accepts composite video input and allows it to be
displayed either full screen or in a window.


All 4 of the 1833 radars on the Furuno site list the ARP11 as an option.
Look under "Features/Specs".

"BOEING377" wrote in message
...
When will GPS compasses come down in price? Just came from the bridge of
an APL
container ship where they had two Sperry GPS compasses. They have replaced
mech
gyros on many ships and are very accurate and responsive. Cost about
$17,000.00
each.

Furuno makes GPS compasses is the $ 5-8K range. A GPS compass is an entirely
different critter from the NMEA compass information provided from a GPS
sensor. A GPS compass is not using the datastream. It is using three
antennas at least and doing carrier signal phase difference measurements. A
proper installation requires a technician who understand radio wave
reflections, and even he may have to reposition the antenna array a few
times for proper results. It is really trial and error at first. I know of
two identical 80 foot Alaska crab fleet boats, where one system works super
and the other is still fighting problems. And, yes, they provide Furuno
AD-10 format compass data to a radar. A diagnostic program may take 12 hours
to run for results.

Doug K7ABX

On 01 Nov 2004 03:52:11 GMT, (BOEING377) wrote:

When will GPS compasses come down in price? Just came from the bridge of an APL
container ship where they had two Sperry GPS compasses. They have replaced mech
gyros on many ships and are very accurate and responsive. Cost about $17,000.00
each.

17000???

How about the CSI-Wireless Vector Lite? We've been using one for over a year
now on oil rigs.

US$3k.

Dave

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All replies to the group please.

"Doug" wrote in message
news

"BOEING377" wrote in message
...
When will GPS compasses come down in price? Just came from the bridge of
an APL
container ship where they had two Sperry GPS compasses. They have
replaced
mech
gyros on many ships and are very accurate and responsive. Cost about
$17,000.00
each.

Furuno makes GPS compasses is the $ 5-8K range. A GPS compass is an
entirely
different critter from the NMEA compass information provided from a GPS
sensor. A GPS compass is not using the datastream. It is using three
antennas at least and doing carrier signal phase difference measurements.
A
proper installation requires a technician who understand radio wave
reflections, and even he may have to reposition the antenna array a few
times for proper results. It is really trial and error at first. I know of
two identical 80 foot Alaska crab fleet boats, where one system works
super
and the other is still fighting problems. And, yes, they provide Furuno
AD-10 format compass data to a radar. A diagnostic program may take 12
hours
to run for results.

Doug K7ABX



KVH has one for around $3k. Have not seen it in use.

JRC also makes a unit. It uses 2 antennae. Costs about $3,000. Read an
interesting article about these on one of the boating websites. The Furuno
unit has 3 antennae and can calculate additional information, for example,
roll period.

"BOEING377" wrote in message
...
When will GPS compasses come down in price? Just came from the bridge of
an APL
container ship where they had two Sperry GPS compasses. They have replaced
mech
gyros on many ships and are very accurate and responsive. Cost about
$17,000.00
each.