Adjusting a Compass's Magnetic Declination Manually
| Field | Navigation/Survival/Orienteering |
| Went Obsolete | Mid- to late-2000s |
| Made Obsolete By | Rise of personal, affordable GPS units |
| Knowledge Assumed | How to read an isogonic map, how to make simple mechanical adjustments using a screwdriver or similar |
| When useful | When using a compass and requiring a degree of accuracy (esp., when orienteering over large distances where small inaccuracies can cause large margins of error) |
- Locate one's general location on an isogonic map (see below),
- Manually adjust the compass's magnetic declination to the offset specified on the isogonic map (either East, West or none), and
- Test the adjustment by triangulating to known points (benchmarks and/or geologic structures)
Isogonic Map
Map of North America, showing magnetic declination lines.
