The United States National Grid (USNG) provides a way to describe any geographic location in the U.S. with a simple, if cryptic, coordinate reference. For example, the Washington Monument's position can be expressed as 18SUJ20, accurate to 10 km--more precisely, that describes a square 10 km on a side--and by adding more digits, you can specify the location more precisely: 18SUJ23480647 specifies its position accurate to 10 m. Among other things, USNG can be useful during major emergencies such as hurricanes, and various organizations are encouraging its use for such purposes as well as in day-to-day uses such as pointing out locations on a map.
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