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Historical Magnetic Declination

Magnetic declination is an important concept for accurate navigation. A compass will always point along the lines of magnetic force (which converge on what are called the magnetic poles). The angle between the direction of force and the direction of the geographic north pole is called the declination.

600+ government ArcGIS servers with open data

Part 1 – List of 600+ government ArcGIS servers with open data Earlier this year I posted two pdf files with internet addresses for federal and state ArcGIS servers with open data.  That work has now been combined into a single pdf file.  In addition, internet addresses for various regional, […]