Loading ...
Sorry, an error occurred while loading the content.

magnetic declination

Expand Messages
  • dpa_io
    Cross-posted from the DPRG list: Howdy,For those working on outdoor robots navigating to GPS coordinates using a magnetic compass or IMU-based
    Message 1 of 5 , Aug 20, 2014
    • 0 Attachment
      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 
      calculations.
      
      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.
      
      Rats!
      
      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:
      
      http://www.ngdc.noaa.gov/geomag-web/?id=declinationFormId
      
      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?
      
      cheers,
      dpa
      

    • Carol Hazlett
      Thanks for the link!​ On Wed, Aug 20, 2014 at 8:24 AM, davida@smu.edu [SeattleRobotics]
      Message 2 of 5 , Aug 20, 2014
      • 0 Attachment
        Thanks for the link!​


        On Wed, Aug 20, 2014 at 8:24 AM, davida@... [SeattleRobotics] <SeattleRobotics@yahoogroups.com> wrote:
         

        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 
        calculations.
        
        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.
        
        Rats!
        
        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:
        
        http://www.ngdc.noaa.gov/geomag-web/?id=declinationFormId
        
        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?
        
        cheers,
        dpa
        




        --
        Carol Lynn Hazlett
        33801 55th Ave So
        Auburn, WA 98001
        (253) 653-6384


        The secret to creativity is knowing how to hide your sources............Albert Einstein
         



         
         
         
      • Peter Neubauer
        I think you want the World Magnetic Model software from NOAA: http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml This is a software library with C source code
        Message 3 of 5 , Aug 21, 2014
        • 0 Attachment
          I think you want the "World Magnetic Model" software from NOAA:
          http://www.ngdc.noaa.gov/geomag/WMM/soft.shtml

          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.

          -Peter


          On 8/21/2014 12:26 AM, SeattleRobotics@yahoogroups.com wrote:
          >
          > magnetic declination
          > <https://groups.yahoo.com/neo/groups/SeattleRobotics/conversations/topics/48623;_ylc=X3oDMTJyc2Fib2ZoBF9TAzk3MzU5NzE1BGdycElkAzE5NTI0MDQEZ3Jwc3BJZAMxNzA1MTM3MDc4BG1zZ0lkAzQ4NjIzBHNlYwNkbXNnBHNsawN2bXNnBHN0aW1lAzE0MDg2MDU5NzU->
          >
          >
          >
          > 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
          > calculations.
          >
          > 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.
          >
          > Rats!
          >
          > 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:
          >
          > http://www.ngdc.noaa.gov/geomag-web/?id=declinationFormId
          > http://www.ngdc.noaa.gov/geomag-web/?id=declinationFormId
          >
          > 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?
          >
          > cheers,
          > dpa
        • dpa_io
          Thanks Peter. I think that s actually implemented on one of the pull-down tabs at the NOAA site. I looked at the code but it s a bit big for the
          Message 4 of 5 , Aug 22, 2014
          • 0 Attachment
            Thanks Peter.  I think that's actually implemented on one of the pull-down tabs at the NOAA site.   I looked at the code but it's a bit big for the microcontroller I'm using (512k RAM + 512k flash), though maybe a reduced set might be hacked that just returns the variation.   Something to ponder.dpa

          • Dan Tebbs
            Also note, if you use a 4-year-old model, it may need tweaking... http://www.cbsnews.com/news/earths-magnetic-field-is-weakening-10-times-faster/ On Fri, Aug
            Message 5 of 5 , Aug 22, 2014
            • 0 Attachment
              Also note, if you use a 4-year-old model, it may need tweaking...




              On Fri, Aug 22, 2014 at 9:36 AM, davida@... [SeattleRobotics] <SeattleRobotics@yahoogroups.com> wrote:
               

              Thanks Peter.  I think that's actually implemented on one of the pull-down tabs at the NOAA site.   I looked at the code but it's a bit big for the microcontroller I'm using (512k RAM + 512k flash), though maybe a reduced set might be hacked that just returns the variation.   Something to ponder.dpa




              --
              Dan Tebbs
              Auric Consulting LLC
              Ph: 425-577-1688
              Email: DanTebbs@...
              http://www.Linkedin.com/in/dantebbs

            Your message has been successfully submitted and would be delivered to recipients shortly.