GPS interfacing notes for Mapper-3a/London 1.6
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Connection of the GPS receiver to a Psion 3a running Mapper-3a.
==============================================================
Required are:
* Psion 3a with 150k of free system memory
* Installation of Mapper-3a/GB v3.6 or higher or Mapper-3a/London v1.5
  or higher
* 3-Link cable (or customised part thereof, see below)
* GPS receiver with NMEA 0183 v1.5 or higher interface (one of the Garmin
  units is ideal) and data cable

Also recommended are power leads for your 3a and GPS 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.
--------------------
If you already have a GPS, 3-Link etc, then all you probably need is a
custom cable to go from the GPS to the 3-Link podule. You can EITHER
(i) make one of these up yourself, or wire something up from GPS to the
    3-link D-type connectors etc and generally have a whale of a time
    doing it ....
OR
(ii) you can get in touch and I may be able to provide you a lead
    'off-the-shelf' to do the job
OR
(iii) you can get in touch with either Maritec (0141 5542492, they do
     lots of marine cabling to go GPS-Psion) OR even better contact P & K
     Measurements Ltd (see blurb below)

If you haven't yet got a GPS or cable etc and are wanting some advice,
there is a company that specialises in Psion/GPS/car fitting etc. P & K
Measurements Ltd (contact name Peter Kitsen or Tony Denson) do GPS units,
car-cradle for the Psion 3a, cabling, power leads and generally provide a
complete solution (and are happy to mix and match the bits you haven't
got yet!) Give them a call on 01403 271114.

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 satalite
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 Mapper-3a 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!

Steve Litchfield

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 Mapper-3a is 0183
version 1.5. Mapper-3a 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 ....