GPS information shipped with Psi-Mapper/London 1.7
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What's rather caught my imagination here has been the possibility of
hooking the Psion up to a GPS (Global Positioning System) unit, which are
now available for a few hundred pounds (though don't buy the cheaper
models) and which are smaller than the Psion.

In case you're not sure what a GPS is, it's a small unit with a built-in
aerial which receives positioning information from the american GPS
satellite system (see picture) to tell you your current latitude,
longitude, velocity, altitude etc.

By hooking the two together the possibility exists to use the Psion as
a very flashy real-time moving-map display. Of course, if all this seems
like whimsical gadgetry to you, you're probably right, but then I like
gadgets! My Garmin GPS45 cost about 255 including VAT in October 1995
from a London dealer.

Note that ETA etc are calculated using your set average speed in your
personal preferrences. I've tried using actual speed from the GPS etc, but
so far the results are just as transient and and/or approximate as using a
set average ... watch this space ...

So what do you need if you want to try all this out?

   * Psion 3a or 3c with 150k of free system memory (100k needed
     by the program, and 50k margin for other programs you might
     start and stop during the running of Psi-Mapper)
   * Installation of Psi-Mapper/London v1.7.04 or higher
   * PsiWin cable OR 3-Link cable (the part with the 'podule' on)
   * GPS receiver with NMEA 0183 v1.5 or higher interface (one of the
     Garmin units is ideal) and data cable to the 3-Link connector or
     podule.

Also worth thinking about is integrating power leads for your Psion and
GPS into the wiring if you intend to run them both for long periods! Note
that the Psion doesn't *have* to be on all the time, you can just turn on
when you need a 'fix'!

Acquiring the above

I'll assume you already have a Psion and 3-Link, or you probably wouldn't
have got this far! First item on your shopping list is to buy a GPS. The
next bit's the tricky one.

The easy way to connect all this together is to contact Tony Denson or
Peter Kitsen at Positioning Ltd on 01403 271114, as they have the
expertise and stock to put together all the elements you might want, from
cables to cradles. Or try Maritec on 0141 5542492, who do cables from most
GPS systems to the Psion 3-Link podule.

3a owners:
The more 'Do-It-Yourself' approach is to make up, or get made, a cable to
go from the GPS to the Psion podule yourself. As most GPSes have different
connectors, you'll need the specific data cable for your unit from the
manufacturers, which is normally about 20 pounds. You'll then need a
9-pin mini-DIN connector soldering on the end with the bare wires.

3c owners:
Simply use a null-modem adapter between the GPS data cable and the PC end
of the PsiWin cable. If you're not sure what this means, take both cables
to your local computer shop and show them both leads!!

Getting the GPS link working

Assuming you now have all the bits you need:

  1. Plug everything in

  2. Start up the GPS and position in your car to get good satellite
     reception. I find it works very well wedged on top of the dashboard,
     but if you have a heated windscreen this may be a problem for you, as
     the mesh of wires can block the signal.

  3. Start up Psi-Mapper/London and go to the map you want the moving map
     icon displayed on-top of, and set your required sticky
     displays/options. If you're wanting to try out the ETA/Distance left
     option, choose your settings in the 'Moving Map Settings' dialog, and
     'select' a destination (place or overlay item) by 'find'ing it in the
     usual way. When all is ready, select 'GPS Moving Map' from the
     right-hand menu.

  4. If all is well, you'll see one of two icons on your map. Either a
     cross-hair showing current position or a 'Poor GPS' icon. The latter
     will appear whenever your GPS's output quality deteriorates to warn
     you that it doesn't really know where it is anymore. Try waiting or
     re-positioning your GPS ....

  5. If the cross-hairs get too close to the edge of the screen, the map
     will re-centre itself and stay in 'GPS Moving map' mode.

Have fun!

Extra notes

   * If you haven't got a GPS yet, there is a little simulator routine
     built into the program to show you what you'd see

   * If you should blow anything up or injure yourself in any way, please
     note that I take no responsibilty whatsoever for use of this software
     product! And if you're driving, keep your eyes on the road! I mean it!
     ONLY USE THIS PROGRAM ON THE MOVE WHEN SOMEONE ELSE IS DRIVING. IF YOU
     *DO* USE THIS ALONE ON THE MOVE, I WILL NOT BE HELD RESPONSIBLE WHEN
     YOU CRASH HEAD-ON INTO A JUGGERNAUT!!!

   * Technical one, this. Your GPS map datum should be set to WGS 84, if
     it's not already! Also, the NMEA version supported by Psi-Mapper is
     0183 version 1.5. Psi-Mapper gets its information from the NMEA
     sentence $GPRMC, so if your GPS doesn't output this word you're
     stuck! Get in touch and I'll see what I can do ... See also my guide
     on troubleshooting GPS operations at the end of this file.

Recommendations for purchasing a GPS

Don't buy the cheapest models! They may not have the right NMEA computer
interface! Shop around before deciding which model to buy or how much to
pay! Start looking at the Garmin units (30,45,55,65,75,90 etc), which have
a very good reputation.

Places to try in your quest:

   * Positioning Ltd on 01403 271114
   * Pumpkin Marine on 0171 4806630
   * Garmin UK on 01794 519944

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                       Troubleshooting GPS operations

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So, you've been trying out Psi-Mapper on your Psion with your new GPS
gadget. And it doesn't seem to work, either at all or terribly reliably ...
Well, you're in the minority, because there are lots of people out there
using it all quite happily together, but I accept that what with all the
things that could go wrong, a few brief notes might be in order!
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Things to think about and look out for:

   * Are you using the latest version of Psi-Mapper? If not, download it
     from here.

   * Is your GPS 100% compatible with NMEA 0183 v1.5 and above? Psi-Mapper
     needs the $GPRMC word output every 2 seconds or more frequent. The
     best way to check what your GPS is outputting is to install the
     'Comms' app on your Psion (you'll find it on the 'C' drive), set the
     parameters to 4800 baud, 8 bits, no parity, no handshaking, and see
     what appears on your screen. You may find it useful to capture some of
     this output to a text file for later analysis, or for sending in for
     diagnostic purposes.

     Garmin GPSes seem to meet these criteria very easily, other makes tend
     to be more non-standard. In particular, the Magellan GPSes only output
     sub-sets of the NMEA standard data sets. If you've got a Magellan,
     make sure you're using v3.9 of greater of Mapper-3a/GB or v1.7 or
     greater of Psi-Mapper/London, as I've been tweaking the code to work
     more reliably on the Magellan's cut-down NMEA signals.

   * How are you linking the two together? Are you 100% sure the
     pins/wires in your connections aren't shorting or dropping out? Are
     all the cables pressed fully home? Using the pin-outs given in the
     GPS and PsiWin/3-Link manuals, try 'buzzing out' the cables you're
     using to ensure that the signals are going where you think they are!

   * Make sure your GPS's output is in the right NMEA mode. For example,
     the Garmin defaults to using its own proprietary GARMIN/GARMIN mode.

If you've addressed the above and are still having problems, please email
me!

Steve Litchfield
