Learning The Declination For An Area
Most use of declination is in conjunction with a map; as stated, that map may state (or even illustrate) the local declination. If not,
- A general isogonic chart of the world or continent can be consulted for a rough estimate of the local declination (within a few degrees)
- A prediction of the current magnetic declination for a given location (based on a worldwide empirical model of the deep flows described above) can also be obtained on-line from a web page operated by the National Geophysical Data Center, a division of the National Oceanic and Atmospheric Administration of the United States.
One would of course rather have the real declination than a prediction. However, a map is sure to be months or years out of date, whereas the model is built with all the information available to the map makers at the start of the five-year period it is prepared for. The model reflects a highly predictable rate of change, and will usually be more accurate than a map, and almost never less accurate.
Read more about this topic: Magnetic Declination
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