48625Re: [SeattleRobotics] magnetic declination
- Aug 21, 2014I think you want the "World Magnetic Model" software from NOAA:
This is a software library with C source code that calculates the
declination for any location on the earth at any time between the years
2010-2015. Since this library doesn't need an Internet connection, you
could run the model directly on your robot.
On 8/21/2014 12:26 AM, SeattleRobotics@yahoogroups.com wrote:
> magnetic declination
> Wed Aug 20, 2014 8:25 am (PDT) . Posted by:
> dpa_io <mailto:davida@...?subject=Re%3A%20magnetic%20declination>
> Cross-posted from the DPRG list: Howdy,
> For those working on outdoor robots navigating to GPS coordinates using
> a magnetic compass or IMU-based magnetometers, the difference between
> magnetic north and true north needs to be incorporated into the heading
> In the before-time, the local magnetic variation was included in the GPS
> NMEA $GPRMC sentence in fields 10 and 11, but that no longer appears to
> be the case. My GPS currently returns zero for both of those fields,
> and Steve Edwards confirmed this with his GPS at the last RBNO.
> I think the GPS satellite guys just got tired of having to upload new
> magnetic maps all the time. Too bad
> So it looks like for jBot the magnetic variation will need to be entered
> by hand for any particular location. That change has now been made to
> jBot's navigation code.
> There's probably an app for your GPS-equipped smartphone that can return
> the local variation, but I haven't found a good one. In the meantime,
> the NOAA website at:
> provides a calculator that allows you to enter a lat/lon (and date!) and
> returns the correct magnetic variation. For the SMU campus in Dallas it
> currently returns 3.58 degrees E (i.e., add 3.58 to your compass
> heading) and says it changes by 7.5 minutes per year.
> Anybody got a slicker way of automating this process?
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