Empathy List Archives

DC

Dave Cooper

Mon, Jun 4, 2007 1:05 PM

I believe that the projected arrow is from the course info and the ship's
symbol is from the heading info. So if they are not in "approximate"
agreement then you can have two conflicting pieces of information display.
Then it becomes as matter of "which is correct?"

If the ships gyro aka heading input to the AIS box is in error due to being
wired incorrectly or some other issue then they won't even closely agree.
The AIS GPS gives the course, the gyro or whatever is used gives the
heading. A boat making with a heading of 90 degrees with show the ship
oriented in this direction from the heading input however if it is drifting
south then the projection line will be in this direction from the GPS.

So the installation and the frequent check on the transmitted data is
required. I would think that the system would be required to show on another
display your transmitted information....easy cross check and would help to
insure that you have inputted the correct data and that the black boxes
feeding the AIS are doing so correctly. Without this what do you have??

As always YMMV

Cheers
Dave & Nancy
Swan Song
Roughwater 58
Caribbean Cruise '07

<John wrote: I'm used to seeing a projected course track that extends outward from the target, the distance proportional to the ship's speed.> I believe that the projected arrow is from the course info and the ship's symbol is from the heading info. So if they are not in "approximate" agreement then you can have two conflicting pieces of information display. Then it becomes as matter of "which is correct?" If the ships gyro aka heading input to the AIS box is in error due to being wired incorrectly or some other issue then they won't even closely agree. The AIS GPS gives the course, the gyro or whatever is used gives the heading. A boat making with a heading of 90 degrees with show the ship oriented in this direction from the heading input however if it is drifting south then the projection line will be in this direction from the GPS. So the installation and the frequent check on the transmitted data is required. I would think that the system would be required to show on another display your transmitted information....easy cross check and would help to insure that you have inputted the correct data and that the black boxes feeding the AIS are doing so correctly. Without this what do you have?? As always YMMV Cheers Dave & Nancy Swan Song Roughwater 58 Caribbean Cruise '07

JM

John Marshall

Mon, Jun 4, 2007 4:14 PM

The Furuno FA-150 on my boat includes a 12 channel DGPS receiver to
ensure it always has correct internally-generated COG, SOG and
location data. It does not need any external heading input as it
computes it all from its GPS.

I'm not sure about other brands, but given how cheap GPS receivers
are now (even most new cellphones have them for E911 service), I
would be surprised if all currently-sold units don't have an embedded
GPS.

Out of curiosity, I read the manuals on my boat to look for embedded
GPS receivers in various equipment, and found 8 of them. They are
becoming ubiquitous.

If the constellation went dark, we'd have trouble making toast. <grin>

John Marshall
N5520 - Serendipity

s of heading data.
On Jun 4, 2007, at 6:05 AM, Dave Cooper wrote:

I believe that the projected arrow is from the course info and the
ship's
symbol is from the heading info. So if they are not in "approximate"
agreement then you can have two conflicting pieces of information
display.
Then it becomes as matter of "which is correct?"

If the ships gyro aka heading input to the AIS box is in error due
to being
wired incorrectly or some other issue then they won't even closely
agree.
The AIS GPS gives the course, the gyro or whatever is used gives the
heading. A boat making with a heading of 90 degrees with show the ship
oriented in this direction from the heading input however if it is
drifting
south then the projection line will be in this direction from the GPS.

So the installation and the frequent check on the transmitted data is
required. I would think that the system would be required to show
on another
display your transmitted information....easy cross check and would
help to
insure that you have inputted the correct data and that the black
boxes
feeding the AIS are doing so correctly. Without this what do you
have??

As always YMMV

Cheers
Dave & Nancy
Swan Song
Roughwater 58
Caribbean Cruise '07

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The Furuno FA-150 on my boat includes a 12 channel DGPS receiver to ensure it always has correct internally-generated COG, SOG and location data. It does not need any external heading input as it computes it all from its GPS. I'm not sure about other brands, but given how cheap GPS receivers are now (even most new cellphones have them for E911 service), I would be surprised if all currently-sold units don't have an embedded GPS. Out of curiosity, I read the manuals on my boat to look for embedded GPS receivers in various equipment, and found 8 of them. They are becoming ubiquitous. If the constellation went dark, we'd have trouble making toast. <grin> John Marshall N5520 - Serendipity s of heading data. On Jun 4, 2007, at 6:05 AM, Dave Cooper wrote: > <John wrote: I'm used to seeing a projected course track that extends > outward from the target, the distance proportional to the ship's > speed.> > > I believe that the projected arrow is from the course info and the > ship's > symbol is from the heading info. So if they are not in "approximate" > agreement then you can have two conflicting pieces of information > display. > Then it becomes as matter of "which is correct?" > > If the ships gyro aka heading input to the AIS box is in error due > to being > wired incorrectly or some other issue then they won't even closely > agree. > The AIS GPS gives the course, the gyro or whatever is used gives the > heading. A boat making with a heading of 90 degrees with show the ship > oriented in this direction from the heading input however if it is > drifting > south then the projection line will be in this direction from the GPS. > > So the installation and the frequent check on the transmitted data is > required. I would think that the system would be required to show > on another > display your transmitted information....easy cross check and would > help to > insure that you have inputted the correct data and that the black > boxes > feeding the AIS are doing so correctly. Without this what do you > have?? > > As always YMMV > > Cheers > Dave & Nancy > Swan Song > Roughwater 58 > Caribbean Cruise '07 > _______________________________________________ > http://lists.samurai.com/mailman/listinfo/passagemaking-under-power > > To unsubscribe send email to > passagemaking-under-power-request@lists.samurai.com with the word > UNSUBSCRIBE and nothing else in the subject or body of the message. > > Passagemaking Under Power and PUP are trademarks of Water World > Productions, formerly known as Trawler World Productions.

RR

Ron Rogers

Mon, Jun 4, 2007 5:01 PM

You can always check vessels in radar range. In decent weather, we've got
binoculars. John used his eyes to correct the AIS data.

Ron Rogers

----- Original Message -----
From: "Dave Cooper" swansong@gmn-usa.com

| <John wrote: I'm used to seeing a projected course track that extends
| outward from the target, the distance proportional to the ship's speed.>
|
| I believe that the projected arrow is from the course info and the ship's
| symbol is from the heading info. So if they are not in "approximate"
| agreement then you can have two conflicting pieces of information display.
| Then it becomes as matter of "which is correct?"
|
| If the ships gyro aka heading input to the AIS box is in error due to
being
| wired incorrectly or some other issue then they won't even closely agree.
| The AIS GPS gives the course, the gyro or whatever is used gives the
| heading. A boat making with a heading of 90 degrees with show the ship
| oriented in this direction from the heading input however if it is
drifting
| south then the projection line will be in this direction from the GPS.
|
| So the installation and the frequent check on the transmitted data is
| required. I would think that the system would be required to show on
another
| display your transmitted information....easy cross check and would help to
| insure that you have inputted the correct data and that the black boxes
| feeding the AIS are doing so correctly. Without this what do you have??

You can always check vessels in radar range. In decent weather, we've got binoculars. John used his eyes to correct the AIS data. Ron Rogers ----- Original Message ----- From: "Dave Cooper" <swansong@gmn-usa.com> | <John wrote: I'm used to seeing a projected course track that extends | outward from the target, the distance proportional to the ship's speed.> | | I believe that the projected arrow is from the course info and the ship's | symbol is from the heading info. So if they are not in "approximate" | agreement then you can have two conflicting pieces of information display. | Then it becomes as matter of "which is correct?" | | If the ships gyro aka heading input to the AIS box is in error due to being | wired incorrectly or some other issue then they won't even closely agree. | The AIS GPS gives the course, the gyro or whatever is used gives the | heading. A boat making with a heading of 90 degrees with show the ship | oriented in this direction from the heading input however if it is drifting | south then the projection line will be in this direction from the GPS. | | So the installation and the frequent check on the transmitted data is | required. I would think that the system would be required to show on another | display your transmitted information....easy cross check and would help to | insure that you have inputted the correct data and that the black boxes | feeding the AIS are doing so correctly. Without this what do you have??

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Re: [PUP] AIS pitfalls