Can I

Ah widnae choose a hand-held tae sustain fixed equipment, ah'd choose a fixed gps. Ye ken well yer fergetful, an it wid ony be a matter o' time afore yid hae left it in ra espace gliv box. An' all yer greeting widnae dee nae guid win ye discovered ra art o conversation was short o' ra braw gps speaker..

Despite the twaddle you'll read a gps output will feed many sources, certainly more than 3 if it's a garmin. The more ouputs you feed with a gps set (DSC,PC etc) the more exposed you are to failure. Make such wiring permanent to a fixed gps, and use your handheld as a backup.
 
In English now, go your Garmin store and ask for such a cable, they are standard issue. Although I'm with young tome regarding buying (ooh there's a swear word that will get through the checker) a fixed unit and using the handheld as a backup. You can get one for around £150.
 
Claymore,
I did it and it works. Icom DSC as well. GPS not Garmin but handheld SLR, doesn't matter, the signal output is NMEA anyway. I've set the same kind of connector to switch from laptop to autopilot.

good luck
Jose
 
The serial port on most portable PC’s is the male nine pin socket at the back of the computer. Only two of the nine pins are used for the GPS connection, No. 2 is for data out of the PC, N0 3 is for NMEA data in to the PC (look at a nine pin plug with your best reading glasses on and they will usually be marked in tiny letters). See the diagram below
GPSwiring.JPG

These two pins are connected to the NMEA In and NMEA Out wires from your GPS (look at your GPS manual, and there will be instructions on how to find these). Larger GPS have dedicated outputs to run Yeoman plotters, electronic charts and so on, but even handheld GPS have an accessory to plug in to give you a NMEA feed. You often need to configure the GPS to send an NMEA signal down the wire you will be connecting to your PC. Have a look in the GPS manual.

The easiest way to make a lead to connect your GPS to your computer is to buy a computer cable of any type that had a female nine pin plug on the end. You can even use an old mouse or other cable, provided it has a plug which fits the back of the PC. Chop off the cable to a suitable length, identify pins two and three using the continuity tester on your electrical meter, and splice in the wires to the feed from your GPS. Some GPS will advise you to also connect a ground or earth pin from the GPS to the computer

Troubleshooting your GPS/PC Interface: You can “see” a GPS signal using your electrical meter, so you will know if you have a live plug with the correct connections. Set you electrical meter to read something under 10v DC, and check the plug connections. A GPS signal looks like “Positive volts…No volts…Positive volts…No Volts…Positive volts…No volts…..” at about half second intervals. If you have an external GPS aerial, these are usually stand alone GPS engines – all you need is to apply power, and they will give you an NMEA signal with position, handy if your expensive interface packs up.

The next way to check your GPS signal is to use the “Hyperterminal” facility on your pc. (found under Start – Programs – Communications – Hyperterminal). Create a new connection (choose an icon and a name). Make sure you select “connect using Com 1” – the nine pin plug on the back of your pc. Hyperterminal will usually automatically sense the type of signal it receives - if you have to set it manually, the format is normally 4,800 baud, 8 bits, no parity, one stop bit. When you connect, you will see string of characters which look like this:

$IIRMC,230316,A,1636.992,S,15133.741,W,0.00,0,100801,12,E*67

If you do, you have got a good NMEA signal!
 
Thrilled to my Knickertops

This post started so badly with wee jamesie but I ended up with the best, most reasoned and explicit instructions and advice I've ever gained in my life - apart from once when my old Dad caught me with Sandra Plumbe, but thats a long time ago and he was quite right - she turned out exactly like her mother
Thank you all very much.
 
Just a slight correction if I can be so bold! Connect the data in wire to the GPS also. That way you can download routes and waypoints from the PC to the GPS, which a lot of plotting packages will allow.

Was that really your position on 10th August 01?
 
$IIRMC,230316,A,1636.992,S,15133.741,W,0.00,0,100801,12,E*67

Lets see, time RMC = Recommended minimum specific GPS/Transit data
UTC 23:03:16, A=receiver warning OK, 163deg 6.992min South, 151deg 33.741W, 0.00knts speed over ground, 0deg True course, 10th Aug 01, Mag Var 12deg E, *67 Checksum

Or something like that
 
Ok, you got the Mag Var 12 deg E. The position (close to shore) plus zero speed indicates the boat was at anchor.

The sentence starts II. If it was direct from a GPS receiver it would start GP (ie GPRMC), therefore this has come via an Integrated Instrumentation system, which means it was almost certainly a Raymarine GPS connected to the outside world via their NMEA bridge.

You might want to revisit your latitude- never seen 163 degrees yet!

There's a lot of forensic information in NMEA character strings.
 
You must log in or register to reply here.

Share this page

Top