Does anyone really know what time it is? - Page 2 - SailNet Community
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post #11 of 14 Old 07-29-2015 Thread Starter
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Re: Does anyone really know what time it is?

Quote:
Originally Posted by gbgreen59 View Post
Sort of a built in "end of life" feature.
Interesting concept. Of course I despise Raymarine equipment. They have gone bankrupt more times then I have been married + the number of my children (a 3 bit integer!) I don't understand why builders like Catalina still put their crap on boats.

I did some playing around and discovered that:

1) This particular "mushroom" came in both a Seatalk (tm) and NMEA version.

2) When I disconnected the Seatalk (tm) lead from the autopilot computer the control head at the helm started reading out the correct date and other data. So Raymarine at least bridged the Seatalk (tm) and NMEA data in the autopilot computer for GPS data. They have a habit of dropping NMEA sentences between NMEA "In" and "Out", one of the reasons I hate them.

3) The autopilot control display immediately started displaying the same information that appeared on the Garmin Multifunction displays (5212 & 5012.) They had always been slightly out of sync. I had just written it off to a network interfacing issue. Now I know that the autopilot computer was getting the wrong data from the GPS mushroom. Obviously it was using that data as the "preferred" data. Since the Seatalk (tm) bus was powered by the autopilot computer I never saw the condition without the GPS mushroom until I actually disconnected ti electrically.

4) I have posted this on the Raymarine web site. We will see what they say.

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post #12 of 14 Old 07-29-2015
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Re: Does anyone really know what time it is?

Wow, how interesting is that? Pretty cool experiment, and gave insightful results.

If I'm right about the roll-over issue, then you will probably just have to toss the mushroom GPS. The issue isn't uncommon for really old GPS. Always seemed short sighted from a SW design point of view. On the other hand, memory and processor speed were much less capable back then. SW designers were doing all they could to save on storage and throughput. Not so tough now.
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post #13 of 14 Old 07-29-2015
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Re: Does anyone really know what time it is?

I think perhaps you have the right idea, but are missing the problem. Most likely, the GPS mushroom or the nema converter does not provide date. Virtually all 183 sentences that need it only have time. Position is dependent on time differences, not absolute time. So they didn't require date.

So more than likely, your MFD just simply used its date it had stored. Perhaps it's build date.

Any thoughts?
Bryce

Last edited by BryceGTX; 07-30-2015 at 12:41 AM.
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post #14 of 14 Old 08-03-2015
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Re: Does anyone really know what time it is?

Quote:
Originally Posted by BryceGTX View Post
I think perhaps you have the right idea, but are missing the problem. Most likely, the GPS mushroom or the nema converter does not provide date. Virtually all 183 sentences that need it only have time. Position is dependent on time differences, not absolute time. So they didn't require date.

So more than likely, your MFD just simply used its date it had stored. Perhaps it's build date.

Any thoughts?
Bryce
Are you saying that date/time isn't needed, computed or output from a GPS receiver?

Last edited by gbgreen59; 08-03-2015 at 10:19 AM. Reason: added "date" to sentence
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