Wireless communication between GPS-unit on dinghy, GPS-unit on bouye and watch?

Discussion in 'OnBoard Electronics & Controls' started by MrSantiago, May 2, 2009.

  1. MrSantiago
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    MrSantiago New Member

    For my final exam in industrial design I am creating a design concept for an allround GPS training system for dinghy sailors.

    Basically the concept is about attaching units with GPS receivers to the dingys and the bouyes used in training, and making that data avaliable on a watch on the sailors arm, so he can read his VMG to the mark.

    Does anyone know what would be the best wireless form of communication between the units on the dinghy and bouyes and the watch?

    The units already use GSM to brodcast the data to a server. So my guess is that the watch also could receive data from the server (about the bouyes and dinghys position via GSM)

    Another important feature is that the sailors also will be using the watch as a dictaphone during training, only for short messages. The audio also needs to be send to the server as well.

    But that is a lot of sim-cards and data GSM communication that costs money and maybe presents significant latency.

    Does anyone know of a maybe cheaper or better communication solution for this setup?
     
  2. Tim B
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    Tim B Senior Member

    This sounds like a very elaborate solution for this problem.

    Firstly, do you need GPS locations from the bouys at intervals? or do you just need to know a fixed location? I would take a reading on GPS when the bouy was first laid and use that unless you move the mark.

    Communication is the next issue. This is purely down to the operating range you wish to use, again, the GSM/GPRS system sounds like overkill. For full-size racing yachts, it's ok, but for dinghies, I think you'd be ok with bluetooth, as ranges of 1000m are available.

    I guess you're thinking of a shore-based server and display for classroom training. You might be able to use a much smaller data aquisition system which could run from a safety/training boat, hence cutting the range down. This aquisition system could be based on a PIC or an SBC.

    Also, are you fixed to the watch form-factor? It seems quite restrictive. If you are not, many generic hand-held GPS units will give the read-outs you want. You can then use some custom electronics (1 PIC and bluetooth interface with MAX232s for signal conditioning) to do your data transmission in a small plastic box.

    GPS tracking devices are around everywhere these days, so you might want to google some. GSM will get pricey if you deploy a lot of units, so that is worth thinking about.

    Best of Luck,

    Tim B.
     
  3. MrSantiago
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    MrSantiago New Member

    Thanks for the quick reply.

    To answer your questions:

    It is probably enough to take a reading on the GPS when the bouy is first laid. Thanks for the hint.

    Part of the exam is to design that watch, so I am pretty fixed on the form-factor there.

    I didn't know that bluetooth had such a long range on water. Good to know.

    I have one concern though, which I forgot to mention in the previous post.

    What happens when the boat tilts and the sailor falls in the water? I guess the bluetooth-pairing will be lost, but can the units pair up easy again?

    I am thinking about my bluetooth mouse which pairs automatically with my computer 9 out of 10 times. But the 10th time I have to force them to pair.

    Thanks again for you thoughts on this topic

    Y. Santiago
     
  4. Tim B
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    Tim B Senior Member

    I hadn't thought of the effect of falling in the water! It would be worth putting in some error-checking and forcing a reconnect in firmware to overcome that problem.

    Another thought, could you get the watch to talk to an on-board system (this makes most of the electronics easier and cheaper to build), so that the onboard system just sends speed/vmg etc. and the watch is just a display terminal?

    Cheers,

    Tim B.
     
  5. MrSantiago
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    MrSantiago New Member

    It is an on-board system, and the watch is just a display-terminal.

    Do you think it is possible to get the error-checking to work perfect, so the units will connect automatically every single time?

    Cheers

    Y. Santiago
     
  6. Tim B
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    Tim B Senior Member

    It's possible. If you send a check and repsonse it should be easy enough. Timeout if there is no response and attempt to re-pair. Check out this site for ideas (I have no afilliation) http://www.sparkfun.com

    Cheers,

    Tim B.
     
  7. Tim B
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    Tim B Senior Member

    Another thought...

    Could you use AIS to report the position back to shore? then use short-range wireless in the watch?

    Tim b.
     
  8. tspeer
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    tspeer Senior Member

    You might examine your requirements. Vmg to the mark is of comparatively little use, except on reaching legs. It's least useful on a beat. The reason is because Vmg to the mark is maximized when the boat is on the lay-line to the mark. And just prior to tacking on the lay-line, the Vmg to the mark is zero! What a sailor needs to know is Vmg with respect to the wind.

    What a sailor would really like to know is bearing to the mark, especially when they cannot see it, and weather conditions at the mark. A wrist-mounted display with an arrow that always points at the mark, regardless of the orientation of the display, would be very useful.

    And to know how the wind conditions at the boat compare with wind conditions at the buoy would help the sailor to know what to expect from the wind in the future.
     
  9. gonzo
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    gonzo Senior Member

    I think a watch is a bad setup. Anyone that sails dinghies, specially beginners, have their hands occupied. A head phone would be better
     
  10. gonzo
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    gonzo Senior Member

    How are you accounting for wind shifts?
     
  11. Murray Peterson
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    Murray Peterson Structural Engineer

    Low power (<1 watt) NMEA0183 format data strings on CH70 VHF (or whatever the marine VHF data chanel is in Danish waters) would appear to be a good idea and it would also alert other vessels in the area of the presence of sailing dingies and bouys. It would require that the dingies and bouys were all allocated an MMSI number, but that would be good for the safety of the trainees as well.
     
  12. Tim B
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    Tim B Senior Member

    So AIS for bouys and all small craft, then? It's a good idea, but I doubt the dinghy sailors (myself included) will like the extra cost of carrying an AIS transmitter!

    Tim B.
     
  13. goboatingnow
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    goboatingnow Junior Member

    I and many internet definitions say that VMG iis velocity made good towards a destination mark, ie the vector component from you to the mark

    VMG to the mark is useful in any situation where you cannot lay the mark direcly, ie mark to windward, or unable to sail deep downwind

    As to communcations systems, why not consider low power narrow band FM, cheap , good range ( 3-10Kms). reliable etc.
     
  14. Murray Peterson
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    Murray Peterson Structural Engineer

    My suggestion is to manufacture a low power CH70 transciever as part of the units. It does not have to be expensive, high power AIS or DSC radio equipment. It does not have to meet the requirements for AIS transponders approved for use in large ships.
     

  15. Tim B
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    Tim B Senior Member

    My comment was a little tongue-in-cheek, but it is essentially what you are suggesting. A way of identifying floating objects and provide details of such over a broadcast radio system.

    Tim B.
     
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