[aprssig] NMEA output GPS or compass?

John Gorkos jgorkos at gmail.com
Fri Jun 29 13:52:36 EDT 2018

I'm a little late to this, but what input is the LD-250 looking for?
If it's straight NMEA with GPHDT sentences, why not just build your own
little device to do that?  Seems to me, you could do the whole thing for
about $80:  a $10 Atmega µProcessor like a trinket, a $15 triple-axis
accelerometer board with a LSM303DLHC chip on it, and a $40 GPS board
with NMEA out.  Throw in a $10 level converter to get the output signals
up to "true" RS-232 levels, and put a little glue code in there to
generate the GPHDT sentence and mix it with the NMEA stream from the
GPS, and put it all in a nice little box with a power plug on it.

Heck, send me $80 and give me a week, and I'll send you the box.  I've
got everything I need sitting here on my test bench.

John Gorkos

On 6/29/18 10:27, david vanhorn wrote:
> Thanks all. 
> I am going to hold off till I find a fluxgate compass.  The GPS route
> would "work" but this thing has enough issues already.
> The Boltek LD-250 is " Long Range detection Designed for mobile use in a
> moving vehicle with a GPS or Compass connected " (From their web site)
> However..
> Their software doesn't work with any known map program.
> The unit sends strike information as bearing and distance relative to
> the front side of the sensor.
> If you add a compass, the strikes are rotated accordingly.
> The strikes are not converted to anything like an object at a coordinate
> though, so if the vehicle is moving, they are "smeared" across the map.
> It's only really useful while moving if the strikes are converted to
> absolute rather than relative coordinates, and then the image is rotated
> and panned accordingly to the vehicle rotation and motion.
> I could easily live without an actual map
> The GPS wouldn't give me workable heading data when not moving, and the
> LD-250 doesn't give useful data while I am moving..
> With a compass, at least I could park in whatever direction works, and
> I'd get a display rotated so that it's oriented north up.
> It's a fixed location instrument in a mobile package.   The only plus is
> that it doesn't require a full PC with PCI slot to run.
> Basically, in the 10 years since I last used it, the half-assed
> implementation of their software hasn't improved at all.   I need it to
> be at least 3/4 assed. :)
> It would be really cool if some working mobile app/program whatever
> could be trained to hear their data and plot it on a working map.
>   $WIMLI,<ddd>,<uuu>,<bbb.b>*<cs><cr><lf>
> <ddd> - corrected strike distance 0-300 miles
>   <uuu> - uncorrected strike distance 0-300 miles
> <bbb.b> - bearing to strike 000.0-359.9 degrees
>        <cs> - checksum in hex
>    <cr> - carriage return
>    <lf> - line feed
> http://www.boltek.com/manual-ld-250.pdf
> On Thu, Jun 28, 2018 at 7:25 AM, david vanhorn <kc6ete at gmail.com
> <mailto:kc6ete at gmail.com>> wrote:
>     I'm reactivating an old project, and I would like to find an NMEA
>     output GPS unit like the old Garmins with their four pin connector,
>     or a compass with similar output.
>     What I've seen in compasses are crazy expensive ($500), and GPS
>     units seem to all be USB output now if they have any external data
>     connection at all.
>     What I absolutely need at a minimum is a compass or GPS with an NMEA
>     output. The system has NMEA+ NMEA-, +12V power to compass/GPS and
>     ground.  If it's a GPS unit, I would prefer some sort of simple
>     "puck" style unit rather than something with a display and buttons
>     to misconfigure.
>     Any sources coming to mind?
>     -- 
>     K1FZY (WA4TPW) SK  9/29/37-4/13/15
> -- 
> K1FZY (WA4TPW) SK  9/29/37-4/13/15
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