Name: Ed M.
How does one compare headings on deeds in NJ relative to
magnetic north over the period 1878 to today. Some date indicates the
drift is as much as 0.15 degrees per year?
The drift in the magnetic field is significant,
as you have alluded to. You could use historical
maps to get the information that you need, if
they are available or you can use a model, such as
GEOMAG, available at www.usgs.gov
Once on the USGS site, do a search for geomag. At
the top of the list you should see "Geomag Program
Download Form". You can download the most recent
program. I'm not sure how far back in time this
program will allow you to go. USGS probably also
has historical magnetic field maps; you may have to
send them an email from their web site to find out
more about this.
David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory
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Update: June 2012