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which model to determine the magnetic declination is more accurate WMM (2014-2019) or IGRF (1590-2019)? I just wanted to determine the magnetic declination for calibration TruPulse Laser Rangefinder. I did not know which model would give me greater precision measurements (Azimuth+Distance)+(GPS+GIS)

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  • they have created more than one for specific reasons. That would help you determine what you need. noaanews.noaa.gov/stories2014/20141215_worldmagneticmodel.html and ngdc.noaa.gov/geomag/WMM simply state that the model has been updated for accuracy and is updated every 5 yrs (for accuracy). If you need it for navigation. accuracy would be pertinent.
    – Brad Nesom
    Commented Feb 6, 2015 at 18:27
  • Brad, unfortunately both of those links have disappeared; if you know the new location could you update them? Commented Aug 2, 2020 at 14:38

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Essentially, it doesn't matter.

From https://www.ngdc.noaa.gov/geomag/faqgeom.shtml#What_is_the_difference_between_IGRF_and_WMM_models :

The IGRF and WMM are both estimated from the most recent data and are of comparable quality.

It does state that WMM is a 'predictive model only', and IGRF is 'retrospectively updated' which I take to mean IGRF allows for historic use (showing what it was) whereas WMM is only valid for the period of the model. Since you're looking for a current setting, either will serve. I note the sample I put in on their calculator is the same or within margin of error for both. WMM returns 8 degrees 39 minutes plus or minus 21 minutes, while IGRF returns 8 degrees 40 minutes (no plus or minus). Both say it moves west at 6 minutes per year.

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  • Chris, unfortunately both of those links have disappeared. If you know where they are now could you edit them in your answer? Commented Aug 2, 2020 at 14:39
  • @markgalassi Apparently there was a department or whatever name change and associated website restructuring. For whatever reason the links still use the old name abbreviation (NGDC) so it's possible they will again change at some point in the future to the new one (NCEI). A Google search for "magnetic declination calculator" had the relevant pages in the first few results should they break again.
    – Chris W
    Commented Aug 3, 2020 at 17:06

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