GPS based data acquisition?

[phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org]

> Folks -
>
> As part of an ongoing study of light pollution, I'd like to be able to
> automatically acquire data from a light meter and plot it on a map, while
> driving over a route.
>
> I have the light meter sorted out: it's a voltmeter equipped with a light
> sensor. The voltmeter can be queried from a PC host over a USB connection
> and provide an ASCII data string representing light level. The voltmeter
> appears to be a serial port periferal.
>
> I have a GPS receiver (the microsoft 'streets and trips hardware) that
> talks to its software via USB, and I suspect it looks like a serial port
> device. However, I can buy some other hardware if that simplifies the
> application.
>
> So what is needed is some sort of app that can be programmed to fire
> requests to a 'serial port device' and then simultaneously capture the
> data that comes back and the GPS coordinates.
>
> Anyone have suggestions where to start with this?

OK, I made some progress on this. I discovered that the Pharos GPS-500 is
a 'serial-USB' device, which is very familiar since that's how we
communicate with our instruments. (This hardware was bundled with
Microsoft Streets and Maps. Hugh posted a notice that it was on sale for
something like $30 at one of the computer warehouse outlets, which is a
great bargain.).

I plugged it into a USB port, and it showed up (according to 'dmesg') on
/dev/ttyUSB0. The default baud rate is 4800, so I started up GTKTERM with
that port setting and baud rate and bingo! the terminal shows a stream of
ascii messages from the GPS.

There may be some advantages to using 'gpsd' as an intermediary, but in
any case we can just decode the ASCII data.

Our voltmeter software can be set to acquire data at any rate (over about
2 readings per second), so I picture patching that with a routine that
captures the most recent GPS data. The same routine would write a
voltmeter-data plus gps-data record to a file.

Now I need to figure out how that data could be superimposed on a map...

Peter

-- 
Peter Hiscocks
Syscomp Electronic Design Limited, Toronto
http://www.syscompdesign.com
USB Oscilloscope and Waveform Generator
647-839-0325

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