Hi all,
I am unable to understand how to get this field from a RMC sentence, on
the GPS I am using (LS20031) the field is empy so I am wondering if this
is just a problem of implementation or what.
AFAIK, the data is highly variable (location and time) so how is the
GPS module able to
The GPS receiver can only compute the direction to true north if the
antenna is on a moving vehicle. The GPS looks backward to where you
were in the last few seconds and computers the direction of travel.
On a fixed antenna this can't work.
But even at best the GPS' idea of north is poor. I had
Garmin receivers provide that data in their RMC sentence. They
apparently calculate it automatically using a mathematical model of
the earth's magnetic field, so its accuracy would depend on the
accuracy of the model. The GPS system itself does not provide a way
to measure variation.
With the
: Saturday, February 05, 2011 5:47 PM
Subject: Re: [time-nuts] OT- RMC sentence and magnetic
variation/compensation in GPS module
The GPS receiver can only compute the direction to true north if the
antenna is on a moving vehicle. The GPS looks backward to where you
were in the last few seconds
Thanks to all for your answers. I am designing a low cost automagic
satellite dish pointer.
I was thinking that adding the magnetic compensation to the magnetic
compass would be neat, but obviously I can't get it from the internet,
still wondering how the GPS could provide a useful value if
but obviously I can't get it from the internet
Are you sure?
still wondering how the GPS could provide a useful value if the modeling is
difficult, varying widely in time and space.
If you ignore local quirks like big chunks of iron ore, the magnetic
declination is a set of smoothly
Are you sure?
I guess so, it is a motorhome traveling South and Central Europe without
Internet connectivity. Really how could Garmin and others provide such data? Do
they allow the user to upload the maps? Never heard about it, but I may be
wrong.
Giuseppe Marullo
At 12:47 PM 2/5/2011, Chris Albertson wrote...
But magnetic variation can be can be gotten from a map...
Compensation would always need to be entered by hand.
Compensation? Please don't tell me they've changed things, and a great
mnemonic is no more. I learned it as
At 00:31 06-02-11, you wrote:
At 12:47 PM 2/5/2011, Chris Albertson wrote...
But magnetic variation can be can be gotten from a map..
e.g. http://www.intermagnet.org/apps/plt/dataplot_e.php?plot_type=dif_plot
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