declination calculator - SERP Analysis

https://www.ngdc.noaa.gov/geomag-web/

https://www.magnetic-declination.com/

https://www.geomag.nrcan.gc.ca/mag_fld/magdec-en.php

https://www.ngdc.noaa.gov/geomag/calculators/magcalc.shtml%3FuseFullSite%3Dtrue

https://www.alpinesavvy.com/blog/find-the-correct-declination-for-anywhere

https://www.omnicalculator.com/physics/magnetic-declination

https://web.cliveruggles.com/tools/declination-calculator

https://geomag.bgs.ac.uk/data_service/models_compass/wmm_calc.html

https://www.usgs.gov/educational-resources/method-1

https://help.campbellsci.com/windsonic1/windsonic/shared/windsonic-orientation/magnetic-declination-calculator.htm