SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/scout-old-map-declination

Why might the declination printed on an old topo map be wrong today?

Magnetic north moves, so declination changes over time.

  1. Paper maps shrink a little every year
  2. True north moves a few miles every year
  3. Magnetic north shifts, so declination changes over time ✔

Why: Declination changes over time and with location because Earth's magnetic field drifts. USGS warns that values on old maps may no longer be accurate, so check a current value.

Huh, didn't know that: USGS says declination values on current maps come from NOAA.

The dad joke
My old map and I have something in common. We are both a little out of date.
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Sources

  1. USGS FAQ: What do the different north arrows on a USGS topographic map mean? https://www.usgs.gov/faqs/what-do-different-north-arrows-a-usgs-topographic-map-mean
  2. NOAA NCEI: Magnetic Declination https://www.ncei.noaa.gov/products/magnetic-declination

Test yourself in the game

Outdoors & CampingOn a map and compass, what is magnetic declination?Outdoors & CampingOn a topographic map, what does a contour line connect?Outdoors & CampingContour lines on your map are packed very close together. What does that mean?

That's stuff everyone should know.