I had read that Magnetic pole is moving impacting declination but I really hadn't let is impact backcountry navigation until yesterday. I was following my very hard to follow AT boundary section and kept ending up off the line. The monument tablets are usually about 900 yards apart unless the terrain is steep. where they will chop up the line into shorter pieces and set an intermediate monument. I had the points plotted in my GPS but usually use my compass to stay on line. I was on a long straight bearing slabbing a steep downhill slope so its quite tough to stay on line to look for blazes. Whenever I looked at my course plot I would be on straight line to the east of my intended route on a fairly straight line. I would then drop down slope and would usually pick up a blaze and then would take another bearing.

My AT boundary maps call out true bearings and when I had corrected the bearing to magnetic I had my compass correction set to 18 degrees which used to be accurate for the area around Andover Maine. I checked the current declination today and its closer to 15. Therefore all my bearings were 3 degrees east of where the actual boundary ran. On 900 yards the error is 236 feet which is enough to get way off a faded intermittently blazed line.