Quick Answer
The US National Geodetic Survey, the National Oceanic and Atmospheric Administration (NOAA), and the World Magnetic Model provide reliable resources for tracking declination changes. These organizations issue regular updates to declination values for different regions. A declination map or calculator can also help track changes over time.
Understanding Declination Changes
Declination is the difference between magnetic north and true north, which can vary depending on your location and time. The US National Geodetic Survey provides declination values for specific points in the United States, updated every 5 years. For example, the 2020 declination value for New York City is -6.2 degrees.
Accessing Declination Resources
NOAA provides a declination calculator that allows you to input your location and obtain the current declination value. The World Magnetic Model, developed by the British Geological Survey and the US National Geophysical Data Center, provides a global declination grid updated every 5 years. This model is essential for precise navigation and orientation.
Utilizing Declination Maps
A declination map can be an effective tool for visualizing declination changes over time. These maps typically display declination values as colors or contours, allowing you to quickly identify areas with significant declination differences. For example, a declination map of Alaska might show a large area with a declination value of -20 degrees, while a nearby region has a value of -5 degrees.
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